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of the
FLORIDA STATE MUSEUM
Biological Sciences
1979
Number 3
BEHAVIOR AND ECOLOGY OF THE ROCK IGUANA
CYCLURA CARINATA
JOHN B. IVERSON
UNIVERSITY OF FLORIDA
Volume 24
GAINESVILLE
Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM, BIOLOGICAL
SCIENCES, are published at irregular intervals. Volumes contain about 300 pages and
are not necessarily completed in any one calendar year.
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ROBERT.W. HENDERSON
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manuscripts should be addressed to: Managing Editor, Bulletin; Florida State
Museum; University of Florida; Gainesville, Florida 32611.
Copyright 1979 by the Florida State Museum of the University of Florida.
This public document was promulgated at an annual cost of
$5,607.48, or $5.607 per copy. It makes available to libraries,
scholars, and all interested persons the results of researches in
the natural sciences, emphasizing the circum-Caribbean region.
Publication date: December 20, 1979
Price, $5.65
BEHAVIOR AND ECOLOGY OF THE ROCK IGUANA
CYCLURA CARINATA
JOHN B. IVERSON'
SYNOPSIS: The natural history and social behavior of the rock iguana, Cyclura carinata,
were studied during 25 weeks between September 1973 and June 1976 on several small
cays in the Turks and Caicos Islands, British West Indies, and in captive enclosures in
Gainesville, Florida.
Reproductive cycles were synchronized to climatic cycles. Testes sizes were max-
imal in April and May (the end of the dry season). Vitellogenesis began in January
(onset of the dry season); ovulation and mating occurred in early May. Courtship was
typical of most iguanid lizards; the mating system was probably one of serial polygyny
with monogamy among some males.
A single annual clutch of 2 to 9 eggs was laid in early June in the terminal portion of
the female's retreat burrow. Clutch size was positively correlated with female size.
Clutch weight averaged about 25% of preoviposition weight. Females defended their
nest burrows for several days to several weeks after nesting, but were not territorial
during the remainder of the year. Hatching occurred after approximately 90 days.
Neonates averaged 79.8 mm SVL and 14.6 gi. Juvenile growth rate averaged 19.2 mm
SVL/year. Males reached sexual maturity at approximately 220 mm SVL and 375-475
gm and at an age of about 7 yr; females 185-200 mm, 200-300 gm at 6 to 7 yr. Adult
males averaged 276 mm SVL and 935 gm, adult females 225 mm and 475 gm. The
largest male measured 360 mm SVL and 1864 gm, largest female 292 mm and 1135 gm.
Adults grew between 2 and 17 mm SVL/year.
Rock iguanas were primarily herbivorous at all ages and fed arboreally and terres-
trially. Five partial septa partition the proximal colon region; this modification presum-
ably increases digestive efficiency. Huge oxyurid nematode populations inhabited the
colon, and their relationship with the iguana may be mutualistic rather than parasitic.
Abdominal fat deposits were negatively correlated with gonadal activity.
Home range size was correlated with body size and habitat productivity, averaging
980 m' for females, 1260 m2 for subdominant males, and 1590 m2 for dominant males.
Diurnal activity was bimodal during warmer months; high midday temperatures
resulted in reduced activity. Winter activity was generally reduced and peaked at mid-
day. Iguanas basked following emergence; most of the remainder of the day was spent
feeding, interacting with other lizards, and shuttling in the sun-shade mosaic for ther-
moregulatory purposes. Basking preceded the termination of daily activity.
Rock iguanas performed ritualized "signature" displays or headbobs. Postural ad-
justments were among the modifiers producing variation in this display in different
behavioral contexts. Displays were important to territory declaration, male challeng-
ing, and sex recognition. Males were territorial year-round in the field, but developed
dominance hierarchies in captivity. Dominant males displayed less than subordinates.
Male territorial defense probably evolved as a mechanism guaranteeing access to food
resources and females for breeding.
The sex ratio was 1:1 in all age classes. Survivorship was positively correlated with
body size. Juvenile densities reached 90.3/ha in optimum habitat, adults exceeded
31.1/ha. Biomass estimates were 5.15 kg/ha for juveniles and 17.01 kg/ha for adults.
Life table data indicate replacement rate was near unity, and mean generation time was
14.0 years. In its life history strategy, C. carinata is a predominately K-selected species.
'The author is an Assistant Professor of Biology, Earlham College, Richmond, Indiana 47374, and an Adjunct
Assistant Curator of Herpetology of the Florida State Museum, Gainesville, Florida 32611.
IVERSON, JOHN B. 1979. Behavior and ecology of the rock iguana Cyclura
carinata. Bull. Florida State Mus., Biol. Sci. Vol. 24(3):175-358.
BULLETIN FLORIDA STATE MUSEUM
TABLE OF CONTENTS
INTRODUCTION... ................ .... ................... .......... 176
A CKNOW LEDGM ENTS ................................................. 182
MATERIALS AND METHODS ...... ............ ................. ..... ....... 182
MORPHOLOGY .. ........ .. ... .... ..................... ........ 188
H ABITAT ............ ...... .. .... .......... ............ .... ....... 193
REPRODUCTION ... ....................... .............. ........... .. 204
G ROWTH ..... ...................... ................ . ......... 247
F OOD AND F EEDING ............... ... ................... ....... . 265
A CTIVITY AND M OVEMENT ............................................... 285
SOCIAL ORGANIZATION .... ...... ....... .......... ...................... 299
INTERSPECIFIC COACTIONS . ..... ........... .. .................. ...... 318
DENSITY AND DEMOGRAPHY ............................................. 325
L ITERATURE C ITED .. ... ... .. ..... ................... ............... 344
INTRODUCTION
PURPOSE
The genus Cyclura is one of the most poorly known lizard genera in
North America, despite being one of the most conspicuous members of
the West Indian fauna. Although a sizable literature exists regarding
the genus, most of the references are faunal lists or general works and
contain only anecdotal information; no thorough autecological study
of any of the species has been made.
Few New World lizards have experienced as intimate a relationship
with man, and suffered more from the interaction, than Cyclura. Major
populations have been extirpated within historic times. Probably no
presently existing population is entirely free from pressures induced
by man and his animals. It is increasingly clear that a thorough
knowledge of the habits and adaptations of our fauna is necessary if we
are to be able to insure their survival in the face of continuing and in-
creasing cohabitation with humans. It was for these reasons that
study was begun on a still relatively common species: Cyclura
carinata, the Turks Island iguana (Fig. 1). From September 1973
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
through June 1976 C. carinata was studied both in the field in the
Turks and Caicos Islands and in the laboratory.
The goals of the study were: (1) to obtain data on the behavior,
adaptations, life history, and community role of this species; (2) to
determine what factors limit population size; (3) to discover methods
by which the species might survive cohabitation with man, without
threat of extinction; and (4) to provide an indepth charter study for ex-
trapolation to similar investigations of other less common and more
endangered species of Cyclura in the West Indies.
SYSTEMATIC RELATIONSHIPS AND DISTRIBUTION
The genus Cyclura is most closely related to the three largest herbi-
vorous iguanine lizard genera inhabiting continental North and Cen-
tral America: Ctenosaura, Iguana, and Sauromalus. On the basis of
myology and osteology Cyclura is most similar to Ctenosaura and next
most similar to Iguana (Avery and Tanner 1971). Endemic to the An-
tilles and Bahamas, Cyclura apparently evolved from a pre-Ctenosaura
stock isolated in the islands. The genera Amblyrhynchus,
Brachylophus, Conolophus, Ctenosaura, Cyclura, Dipsosaurus,
Enyaliosaurus, Iguana, and Sauromalus constitute the subfamily
Iguaninae (Avery and Tanner 1971).
Seven extant species constitute the genus Cyclura, distributed
from the northern Bahamas through the Greater Antilles (Schwartz
and Thomas 1975). Pleistocene remains are known from several islands
within the present range (review in Carey 1975).
Cyclura carinata is closely allied to C. rileyi (San Salvador,
Bahamas). The two species share a number of characters (lack of
enlarged, tubercular, median frontal shields; presence of dorsal crest,
with elongate spines, interrupted on shoulders and rump; maximum
size less than 1 m, etc.) and are both distributed in the southern half of
the Bahaman archipelago.
The relationship of Cyclura ricordi (Hispaniola) to C. carinata
deserves additional study despite the larger size (commonly exceeding
1 m total length) of the former. The two species have similar dorsal
crests and pigmentation patterns and are the only two species of
Cyclura without enlarged supracephalic scales.
STUDY AREA
The Turks and Caicos Islands lie to the southeast of the Bahama
Islands between latitude 21o and 220 N and longitude 710 and 7231'
W (Fig. 2). Although politically distinct from the Bahama Islands, this
1979
BULLETIN FLORIDA STATE MUSEUM
British Crown Colony is geologically part of the Bahaman archipelago.
The islands are situated approximately 150 km north of Hispaniola
and 890 km southeast of Miami, Florida. They consist of two groups of
islands separated by a 35.5 km wide, deep water (> 2200 m) channel,
the Turks Island Passage. The Turks Islands lie east of the passage,
the Caicos to the west. The former consist of two inhabited islands
(Grand Turk and Salt Cay), six uninhabited cays, and numerous
emergent rocks.
The Caicos Islands lie along the perimeter of the Caicos Bank, a
northwest-to-southeast-lying triangular shoal with a base and altitude
of approximately 125 and 75 km, respectively. Depths frequently ex-
ceed 180 m within 2 km of the reefs surrounding the Turks and Caicos
banks. Each of the banks is surrounded by depths of at least 1800 m.
The highest elevation in the islands barely exceeds 85 m (on Providen-
ciales). The present surface area of the islands, as calculated by the
Turks and Caicos Survey Department, is approximately 500 km, with
only 27 km2 in the Turks Islands group. Recent evidence indicates that
shoaling sand is filling many of the cuts, linking previously separated
cays via sandy isthmuses (Noble and Klingel 1932).
Although these changes are usually not rapid, the effects of
tropical storms can be. When Hurricane Donna passed directly over
the Caicos Islands in 1960 the cut between Pine and Water cays was
connected by a sand block. Shoaling since then has nearly filled the
cut. These changes are now, and probably have been in the past, very
important to the dispersal of fauna and flora between islands of the
bank.
.t e"
.- ~ ~ :
FIGURE 1.-Male Cyclura carinata basking on beach at Pine Cay, Turks and Caicos
Islands.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
My studies of Cyclura carinata in the Turks and Caicos Islands
were predominately based in the West Caicos cays. The major islands
comprising this group are, from north to south, Parrot, Dellis, Fort
George, Pine, Water, and Little Water cays (see inset, Fig. 3). Studies
reported here were confined to the latter four. These islands are
phenetically very similar. Each has its leeward sandy beaches, wind-
ward rocky coasts and mangrove swamps, inland brackish water lakes,
northeast-to-southeast-lying karst ridges paralleled by sandy dunes,
maximum elevations of 8 m, vegetation increasing in luxuriance from
west to east, and dense Cyclura populations.
Study was concentrated on Pine Cay, a privately owned island of
nearly 350 ha (Fig. 3). The average elevation on Pine Cay is less than 3
m. Only three points on the island exceed 6 m; the highest point on the
island barely exceeds 8 m. Extraordinary in the Bahama Archipelago,
Pine Cay lies over an impermeable basin, preventing salt water intru-
sion. Maintained solely by rainfall, a freshwater lens sometimes ex-
ceeding 15 m in thickness occupies this basin. Average storage capaci-
ty has been estimated at over 510 million liters. The water table is ex-
posed in seven inland lakes. This availability of fresh water is in part
responsible for the presence on Pine Cay of an extensive stand of
Caribbean pine (Pinus caribaea) found elsewhere in the Bahamas only
on North Caicos, Grand Bahama, Abaco, Andros, and New Providence
(Rabb and Hayden 1957). Vegetation on Pine Cay varies from sparse
on the most recent westerly sand beach ridges to dense on the
geologically older coral ridges to the east with better developed soils
(see Vegetation).
During the summer of 1973, construction began on a private resort
hotel, the Meridian Club, on Pine Cay. I was thus presented with an
opportunity to study the consequences of increased human in-
terference on theretofore relatively undisturbed iguana populations.
ZOOGEOGRAPHIC RELATIONSHIPS
The Turks and Caicos fauna is part of a larger southern Bahaman
faunal group that includes the islands southeast of the Crooked Island
passage, plus Rum Cay and Watling's Island farther north. At least 19
reptiles are endemic to the area, and although strongly divergent,
most have a Greater Antillean ancestry (Schwartz 1968). This is
despite the fact that the Bahaman platform has had its closest
geological relationship with the North American tectonic plate since
Triassic times (Freeland and Dietz 1971).
Among the amphibians, only Hyla naturally reaches into the
southern Bahamas from the north and then only the Mayaguana
passage. None is associated with Cyclura carinata. Over 115 species of
1979
TURKS AND CAICOS
NORTH ATLANTIC OCEAN
ISLANDS
22
.... ......... NORTH
o PINE CAYy 10KM 03
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MIDDLE CAICOS .EAST
WESTT 'CAICOS 0
SCA1COS
S... CAICOS BANK SOUTH
CAICOS
n "".. 0 SIX HILLS CAYS .GRAND
LONG CAY TURK L
.. .- **': ' -' .. .
S. COTTON..
: .. AMBERGRIS CAYS ,; ,, T LII
'" *.. % ........ .. *. -.*
FLORIDA CAY
SCAICOS BUSH CAY
C t' TURKS
8 is.
HATI .. . .. .
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72 71 c
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
FIGURE 3.-Topographic map of Pine Cay, Caicos Islands, showing locations of prin-
cipal study sites: (1) SW Blind, and (2) Ridge Area. Letters A through F indicate sectors
of flush transect route (dotted line). Other trails and roads are not illustrated. Dashed
line encloses limits of Hotel grounds. Unnumbered shaded areas indicate lakes.
BULLETIN FLORIDA STATE MUSEUM
birds have been identified on the Turks and Caicos Islands (Buden,
pers. comm.). Differentiation of at least two of these has occurred
within the southern Bahaman faunal region: Columbina passerina and
Calliphlox evelyane (Bond 1961). The avian species most important to
the biology of Cyclura will be discussed under sections concerning
specific relationships (see INTERSPECIFIC COACTIONS and
FOOD AND FEEDING). Of the depauperate mammalian fauna only
the bat Monophyllus redmani has apparently diverged within the
southern Bahamas (Buden 1975).
ACKNOWLEDGMENTS
I wish to express my sincere gratitude to Walter Auffenberg, chairman of my doc-
toral committee, for his constant aid and encouragement during this study. Thanks
also are due to the other members of my committee: John Kaufmann, Frank Nordlie,
Carter Gilbert, and Willard Payne.
I am particularly grateful to the New York Zoological Society for providing funds
for the field work. Without its support the study would have been infeasible.
Acknowledgment is also given to the University of Florida and the Florida State
Museum for support and space for the duration of my studies.
Of the many people in the Caicos Islands who made this study possible, special
recognition is due C. W. (Liam) Maguire and William and Ginny Cowles of the Meridian
Club, Pine Cay, for their generosity in providing housing, innumerable meals, access to
invaluable maps, and many other courtesies during the study period.
Special thanks are also due Francoise de Rouvray for breaking my monotonous
bean, raisin, peanut butter, and cracker diet with incomparable French cuisine, and to
Gaston Decker for extending every kindness to me while on Pine Cay. They enriched
my visits to the islands more than any other two persons. For similar courtesies I also
thank George and Marou Nipanich. I am also indebted to many other Turks and Caicos
islanders for information and help throughout my study.
Donald Correll, Robert Anderson, and Walter Auffenberg supplemented my plant
collections and identified most of the plants. Donald Buden supplied a list of birds
recorded from the Turks and Caicos Islands. Arthropod identifications were made by
Robert Woodruff (insects), and Martin Muma (solpugids and scorpions).
Walter Auffenberg and David Auth unselfishly allowed me access to their Caicos
Islands field notes. Diderot Gicca and Thomas Wiewandt generously shared with me
their field experiences with other species of Cyclura. Aerial photography of the study
islands was made possible by William and Ginny Cowles. Numerous others have, in one
way or another, added to the successful completion of this work; I apologize for my
failure to acknowledge each one individually.
My wife, Sheila, typed the numerous manuscript drafts, endured my frequent
absences from home, and supported me in many ways during all phases of the work. All
illustrations are the work of the author.
MATERIALS AND METHODS
Preliminary evaluations of Cyclura populations in the Turks and Caicos Islands
were made by Walter Auffenberg between 4 and 14 August 1973. Those investigations
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
revealed Pine Cay in the West Caicos Islands to be the best island for study for several
reasons, including the availability of water and adequate lodging, and the presence of
an extremely dense Cyclura population. Specific study sites on Pine Cay were
designated on my first visit in September 1973.
Eleven trips to the Caicos were made, with 163 days spent on Pine Cay and nearby
islands (15-29 September, 8-22 December, 1973; 2-16 March, 1 June-20 July, 29
August-10 September, 26 November-6 December, 1974; 1-14 April, 29 July-16 August,
4-11 November, 1975; and 1-8 May, 8-15 June, 1976). Twelve additional days were spent
observing and assessing Cyclura populations on numerous eastern islands of the Caicos
Bank. Field notes from the Caicos islands were made available by Walter Auffenberg
(48 study days from September 1973 through 1975) and David Auth (112 days from
June 1974 through February 1976). Copies of all our field notes are filed in the
Herpetological Library of the Florida State Museum.
A site of approximately 0.9 ha in the southwestern corner of Pine Cay was chosen as
my major study area, which was to be used mainly for behavioral observations with as
little interference and manipulation as possible on my part (Fig. 4). The area was initial-
ly chosen due to the abundance of lizard spoor and manure on open areas and the
generally good visibility below the canopy.
An abundance of spoor typically reflects lizard density in the immediate area. Since
Cyclura carinata on Pine Cay was extremely shy, it was necessary to construct a blind
in this southwestern study site. Lizards generally ignored the blind after it had been in
place for only one day. A total of 47 days (287 hr of actual observation) was spent in this
blind during the study period. In order to quantify accurately observed lizard
movements, yellow marker flags, spaced 6 m apart, were placed in a measured grid
system around the blind. Each marker was assigned a letter N (north of the blind) or S
(south), and a number (related to the distance from the blind). Thus a lizard at "N-5
West 3 m" was located 3 m west of marker number "N-5." This greatly increased the
speed and accuracy of data recording and allowed me to tabulate precise lizard
movements. During the course of field work, this entire study area was very thoroughly
and accurately mapped. Surveyors' and topographic maps, prepared under the direc-
tion of Liam Maguire of the Meridian Club and based on numbered cement lot markers
on Pine Cay, and aerial photos made possible precise mapping of lizard and landmark
locations.
Field notes were recorded on a cassette tape recorder each day and transcribed in
the field notebook at night. A Minolta SRT 101 35 mm camera, Sony AV 3400 portable
video camera and recorder, and GAF ST/602 Super 8 movie camera were all employed
to record lizard behavior. More than 1400 slides, 110 minutes of video, and 50 feet of
movie film were taken. The utmost care was always taken at the southwestern blind to
minimize interference with the natural system. Early in the study the resident popula-
tion was marked without handling by means of a "Paint Rifle," a large plastic syringe
firmly mounted on the end of a 1 m, 2 cm diameter, dowel. Maximum range exceeded 10
m, with accuracy possible from 6 to 7 m. Lizards were not at all bothered by this techni-
que. By shooting various colors of paint on various parts of the body, I was able to
recognize individuals. Index cards with outline drawings of the right and left sides of a
lizard were used to record marking and color formation, as well as sex and natural exter-
nal morphological features for each lizard. The cards were modified when parts of the
paint pattern were shed and/or the lizards were remarked. Even after three-month
absences, remnants of paint patterns, in conjunction with activity range and behavioral
information, could be used to re-establish the identity of individual lizards.
As the study progressed, lizards were occasionally noosed from the blind for ac-
curate measurement. In order to attract lizards to the blind for this purpose, as well as
1979
184 IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY 1979
to induce lizard interaction, numerous substances were experimented with as "baits."
Among the items tested were local fruits and flowers, soda and Ritz crackers, peanut
butter, vanilla extract, crab parts, other vertebrate carrion, and sardines. The latter
was the only substance that proved effective as bait, and its effect was striking: adult
males would occasionally cross the territories of at least three other territorial males to
BANK
/
7
/
0 5 IOM
03 UNVEGETATED AREAS
-3-CONTOUR INTERVALS (m)
-R-ROCKY CLIFF
BEACH
* DOMINANT MALE RETREATS
0 OTHER RETREATS
TREE CACTUS
BLIND
+ DISTANCE MARKERS
FIGURE 4.-SW Blind Study Area.
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
obtain the sardines. This bait was, however, less effective during the colder parts of the
year and also when high winds rapidly dissipated the fishy odor. Lizards foreign to the
study site were restrained in hardware cloth cages or on tethers and were sometimes in-
troduced into the activity ranges of established lizards, and the resulting behavioral in-
teractions recorded.
Because lizards on islands with even minimal human traffic were difficult to capture
by noosing except from blinds, this technique was not frequently used on Pine Cay, ex-
cept at the southwestern blind study site (hereafter referred to as the SW Blind). The
technique was, however, fairly successful on islands rarely visited by humans. Juvenile
lizards and occasional adults could be secured by chasing them under rocks or into
hollow logs, from where they could be removed by hand. Noose snare traps and funnel
traps at burrow mouths in areas of great activity were each experimented with, but met
with only minimal success. Lizards were sometimes obtained by removing them from
their burrows. Nests discovered in this process were either removed to the laboratory
or marked for further observations. Numerous freshly killed or mortally wounded in-
dividuals were also secured from the mouths of local dogs and cats. In addition, the
dried remains of many mammal-killed Cyclura were collected. An attempt was made to
collect a sample of at least a few lizards in each season of the year to be used for dissec-
tion. Besides those lizards killed by dogs and cats, the bulk of this sample included
lizards removed from the area on Pine Cay destined for occupation by a hotel and its ad-
joining beach cottages. Since most of these lizards would have been killed by bulldozer
activity, this seemed the best source of material for dissection.
Specimens for dissection were weighed, measured, and preserved in formalin in the
field. Transferred to isopropyl alcohol in the laboratory, preserved specimens were then
autopsied for reproductive condition, gut content, fat bodies, and presence of parasites.
Ovaries, testes, and fat bodies were excised, blotted, and weighed to the nearest 0.01
gm. In females, all yolked ovarian follicles, oviducal eggs, and corpora lutea were
counted and measured to 0.1 mm with dial calipers. Testes volume was determined by
water displacement.
In order to collect data on growth, lizards located in the area immediately adjacent
to the site chosen for construction of the hotel were marked and released on the first
visit to the study island. On each of four succeeding visits within a year no recaptures
were made, despite a continued marking program all along the dunes parallel to the
northwest coast. The disappearance rate in this habitat was obvious on my first return
to the island in December 1973, when not a single iguana was seen in my original mark-
recapture area. A second site was sought, one less disturbed and more densely
populated. In July 1974, another mark and recapture program was initiated on an area
of approximately 1.85 ha on the north end of nearby Little Water Cay (Fig. 5). Habitat
and vegetation there are virtually identical to the areas of Open Scrub on Pine Cay (see
HABITAT). Growth data were also collected on numerous juveniles maintained in the
laboratory on lettuce, cat food, and bean sprouts.
Body length (snout to vent), tail length and condition, body weight (measured to the
nearest five gm), sex (when possible), and any other obvious external morphological
characters (especially in juveniles) were recorded for all lizards during the mark and
recapture program. Maximum height (in mm) and number of annuli on dorsal spines of
the neck, back, and proximal tail regions were also recorded for each adult. Each lizard
was then marked with a unique combination of, at most, two clipped digits and released
as soon as possible following capture (always within the hour). At the SW Blind "belts"
of various colors modified from cat collars were secured around several lizards "waists"
for later recognition.
In addition to lizard movements observed at the SW Blind, it was sometimes possi-
ble in sparsely vegetated sandy areas to map an individual lizard's activity range for a
1979
BULLETIN FLORIDA STATE MUSEUM
single day by his spoor. Since rain and wind quickly obliterate the tracks, this method
is useful only if mapping is done late in the afternoon (following lizard retirement) on
days lacking high winds or precipitation. A 15 m length of kite string was several times
secured around a captured lizard's abdomen just anterior to his hind limbs. On release
he would drag the string through the bush and a small portion of his movements could
later be plotted. The success of this method varied, since the string occasionally became
entangled in brush and was broken. A 3 m length string was similarly employed with
success to locate a captured lizard's home burrows at the SW Blind. Following lizard
submergence, known burrows were checked for string trailing into them.
Lizards were also tracked by radio-telemetry. This technique was used effectively in
lizard displacement and homing experiments as well as for recording daily movements.
All telemetry equipment was purchased from Mini-Mitter Co., Inc., Indianapolis, In-
diana. Transmitters used were Model L Mini-Mitters operating at just over 27 Mhz. A
3-channel Lafayette HA 420 walkie-talkie fitted with a Mini-Mitter Beat Frequency
Oscillator served as a receiver. A Mini-Mitter Model AF Directional Antenna was
employed early in the study; however, technical problems precluded its use for most of
the study. Triangulation by signal strength received from a whip antenna along right
FIGURE 5.-Mark-recapture area on northeast point of Little Water Cay. Study area
(ST) lies within dotted perimeter. Dashed line indicates island shape in 1967 based on
1:10,000 Turks and Caicos topographic series (Land Registration Department, Grand
Turk). Sand from northernmost point has redeposited along a 950 m spit (s) on the Bank
side of the island. Important physical features are included: approximate 1.5 m contour
intervals, pond (P), dune region (D), and mud flats dominated by nearly pure stand of
Rachicallis (R). Vegetation of the study area is typical Open Scrub.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
angle transects proved much more effective, especially in areas of dense vegetation.
The signal with this equipment varied from 100 m in sparsely vegetated dune areas to
just over 50 m in thickly vegetated, rocky areas with greater relief. The range was en-
tirely sufficient for successful use with this species.
Transmitters were secured to the previously described cat collar identification belts
with electricians tape and strapped to the lizard's waist. A short length of twine was
tied to the transmitter package atop the belt. Transmitter retrieval could then be ac-
complished by simply pulling the package from the lizard (leaving the belt in place for
identification) as he lay in his burrow at night or early morning. In this way, a second
disturbance of the monitored lizards was eliminated. The short trailing string did not
seem to bother the lizards nor hamper their movements in any way.
Measures of lizard activity were made in three basic ways: (1) direct observation; (2)
clocking mechanisms at burrow entrances; and (3) flush transects. To record lizard
emergence and submergence times, an alarm clock was remodeled as a single-event
recorder in a technique similar to that of Arlton (1936). A hole was drilled through the
outer case of each of several inexpensive spring wind clocks directly above the timing
wheel. The gravity-operated, tripper mechanism consisted of a small square of card-
board over which an elongate paper clip loop was suspended. A fine nylon thread at-
tached to the cardboard square was stretched across the entrance of a lizard burrow.
Disturbance of the thread removed the cardboard allowing the wire loop to drop
through the timing wheel, stopping the clock.
A flush transect method similar to the 'King strip census' (see Giles 1971 for discus-
sion) was also used for activity patterns as well as density estimates. The technique
consisted of traversing a permanent census trail at different times throughout the day
during each visit to the study island (Fig. 3). Distance along the transect route where
each lizard was flushed and distance from trail to lizard (before being flushed) were
recorded. A total of 103 transects was run during the course of the study. Data from
the flush transects, coupled with direct data at the SW Blind study site provided the
major basis for analysis of activity patterns and estimates of lizard density. In order to
test and insure the accuracy of this transect method, the transect route passed through
the SW Blind site, from which the most reliable density data were presumably
available. The success of flush transects on Pine Cay was the result of the character of
the island itself, as well as that of the lizard. Cyclura on the study island were wary and
typically ran when humans approached. Although many lizards were seen during
transects, the location of most was possible only after they bolted off over noisy leaf lit-
ter. This technique could therefore be successful only in areas where the vegetation was
dense enough to prevent the lizard from seeing the observer until he (the observer) was
within audible range of the noise of his flushing. Such was the case along the transect
route I used.
Lizard burrow structure was investigated by digging up several burrows. Inactive
burrows were usually chosen for excavation in order to minimize interference with
lizard populations. However, several active adult burrows were unearthed in order to
obtain the occupant and to correlate burrow structure with sex and size. Lizards so ob-
tained were either displaced for homing experiments, brought to the laboratory for
behavioral observation, preserved for dissection, or released into nearby inactive bur-
rows after marking. The structure, including length, direction, depth, and substrate for
all parts of each excavated burrow, was recorded. Eggs unearthed in nature, as well as
clutches laid in captivity, were removed to the laboratory in Gainesville for incubation
in moist sand under constant conditions. In an attempt to study turnover rates in bur-
row use, all burrows in a randomly chosen circular area (radius 26 m, area 0.22 ha) along
the limestone ridges of the leeward side of southwestern Pine Cay were surveyed on six
BULLETIN FLORIDA STATE MUSEUM
consecutive visits beginning in December 1973. This site was designated the Ridge
Area (Fig. 3).
Before analysis of diet in this herbivorous lizard was possible, it was necessary to
collect and identify the majority of the plant species on Pine Cay. Plant specimens were
first collected on Pine Cay in September 1973 and recollected seasonally. From these
various collections, a reference catalog of seeds, fruits, and leaves was assembled for
use in identification of lizard food items.
Scat analysis based on 670 fecal pellets supplemented gut content analysis. Plant
species and parts observed being eaten or bearing evidence of iguana feeding (i.e. tooth
marks) were also recorded.
Microhabitat temperatures and precipitation were recorded only when an in-
vestigator was on Pine Cay. Climatic data from Grand Turk Auxiliary Airfield, Grand
Turk (21026'N, 7108'W; elevation 4 m) were also available.
A 3 x 8 x 1.25 m enclosure with attached observation blind was constructed in
Gainesville, Florida, for captive observations. Artificial burrows, water, and an ad
libitum supply of fruits, vegetables, pet food, and sardines were provided.
Several terms used herein require clarification. The "Study Islands" include Fort
George, Pine, Water, and Little Water cays; the "Study Island" refers to only Pine
Cay. The principal study sites on Pine Cay are designated as the SW Blind and Ridge
Area (Fig. 3). Lizard body length or snout-vent length is abbreviated as SVL; tail length
as TL. All references to lizards, rock iguanas, or iguanas, refer to Cyclura carinata
unless otherwise qualified by a scientific name. All material collected incidental to this
study, including other vertebrate and invertebrate specimens, has been placed in the
collections of the Florida State Museum, University of Florida. Statistical methods are
those of Steele and Torrie (1960) unless stated otherwise. Means are ordinarily given
with one standard deviation. Definitions of behavioral terms appear in the text.
MORPHOLOGY
Cyclura carinata Harlan was described in 1825 from "Turk's
Island." The location of Harlan's holotype is unknown. The species
can be diagnosed as follows: nasals broadly in contact with the rostral;
frontal, fronto-parietal, and occipital regions covered by small ir-
regular, strongly keeled scales; circumorbital scales smaller than other
supracephalic scales; 2 to 4 enlarged, vertically arranged canthal
scales on each side; dorsal crest broadly interrupted on the shoulders
and rump; nuchal section of the crest with 16 to 20 spines (up to 2 cm),
which are longer than the 45 to 75 spines on the back; dorsal crest
spines exceed 5 mm in height only in males; femoral pores average 21
on each leg (range 18-25); vertical rows on the tail strongly keeled, with
four vertical scale rows between fifth and sixth rows; mid-dorsal tail
scales enlarged and sharply keeled; males < 80 cm total length,
females < 65 cm.
Two subspecies are recognized. The nominate subspecies can be
distinguished by having the nasals separated by a large wedge-shaped
scale; spinose, hexagonal scales on the outer tibial region, 3 or 4 of
which equal the diameter of the tympanum; and fewer than 60 spines
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
in the dorsal crest. Cyclura c. bartschi, described from Booby Cay, east
of Mayaguana Island, Bahamas Island (Cochran 1931), is character-
ized by nasal scales usually in contact; 4 or more tibial scales equal to
tympanic diameter, and usually more than 60 spines in the dorsal
crest.
The following morphological descriptions are based only on
specimens and data obtained in the Caicos Islands.
DENTITION.-Teeth heterodont, unicuspid at the symphysis and on
premaxillary; remaining anterior teeth strongly tricuspid. Median and
posterior teeth strongly compressed laterally and flared antero-
posteriorly, with a multicuspid cutting edge; large median cusp
flanked by 2-3 smaller anterior and 1-2 posterior cusps. Tooth formula:
0-10 pterygoid; 0 palatine; 4-10 premaxillary; 17-23 maxillary; and
19-28 dentary. Dentition similar to that of other iguanines (all primari-
ly herbivorous) in both tooth counts (Table 1) and presence of increas-
ing cuspidation from anterior to posterior along dentary and maxillary
(see Avery and Tanner 1971 for comparisons). Nearly contiguous,
laterally compressed, multicusped, pleurodont teeth forming con-
tinuous shearing surface, well-adapted for leaf chopping and shearing
(Hotton 1955; Ray 1965; Montanucci 1968). Tooth positions increase
ontogenetically (Fig. 6) as in Ctenosaura, Iguana, and Anolis (Ray
1965; Montanucci 1968). Maxillary and dentary counts positively cor-
related with skull length (r = 0.91 and r = 0.84 respectively).
SKELETON.-Basiphenoid wider than long, slightly to moderately
constricted behind pterygoid processes; length/width ratio: 0.65-0.72.
Five or more foramina on superficial surface of rostral part of premax-
illa; parietal foramen small, pierced in frontal or fronto-parietal suture;
parietal not produced posteriorly; angular and splenial elements pres-
ent; splenial long, narrow; dorso-ventral borders of Meckel's groove
fused anterior to splenial; antero-ventral alveolar foramen partially
enclosed by border of splenial; coronoid with large process overlapping
TABLE 1.-TOOTH POSITION COUNTS IN Cyclura carinata FROM CAICOS ISLANDS, BRITISH
WEST INDIES.
Right Left Right Left Pterygoid
Premaxilla Maxillary Maxillary Dentary Dentary per side
Mean 6.9 19.3 19.3 21.9 21.7 ---
Standard
Deviation 1.4 1.2 1.2 1.5 1.6 ---
Range 4 to 9 17 to 21 17 to 21 19 to 25 20 to 26 1 to 7
Sample 13 14 14 15 14 13
Size
1979
BULLETIN FLORIDA STATE MUSEUM
dentary; postero-ventral angular process pointed, elongate, directed
antero-medially. Usually 24 presacral vertebrate, each with
zygosphenes, zygantra, and zygopophyses. At least some autotomic
caudal vertebrae with two pairs of transverse processes, fracture plane
passing between them. Scapular and secondary coracoid fenestrae
well-developed; clavicles simple or with posterior hook-like processes;
interclavicle T-shaped or arrow-shaped; sternal fontanelle small or ab-
sent; 4 sternal and 2 xiphisternal ribs present. For description of hyoid
apparatus see Avery and Tanner (1971).
HEMIPENIS.-Structure in the genus never illustrated, but that of
C. carinata briefly described by Cope (1896). Hemipenis single-lobed,
subcylindrical to clavate; sulcus spermaticus a broad open groove
along the posterior surface of hemipenis; calyces cover distal half of
hemipenis, proximal half covered with irregular creases; spines or
spinose structures lacking; structure most similar to iguanine genera
Iguana and Amblyrhynchus (Avery and Tanner 1971).
LEPIDOSIs.-Possess corneous subdigital combs on digits 2 and 3
(#4 = longest) of hind limbs (diagnostic of genus); subdigital lamellae
multicarinate, not flattened, lacking mat of hair-like processes. Mid-
dorsal crest spines exhibit considerable sexual size dimorphism (Fig.
7). Female neck spines never exceed 5 mm height (maximum recorded
height, 3 mm). Male neck spines begin development (elongation) with
onset of sexual maturity; thereafter, each time skin is shed, spine in-
26-
O
25-
24-
0
I-
Z 23-
D 0 0
0 22- OD OD
U o oo
21- 0 *
20- 0 0 *
19- *
18-
17- *
30 35 40 45 50 55 60 65 70 75
SKULL LENGTH (mm)
FIGURE 6.-Ontogenetic change in tooth numbers. Skull length measured from snout to
occipital condyle. Maxillary (closed circles) and dentary (open circles) counts are
averages of right and left sides.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
FIGURE 7.-Adult male (A) and female (B) Cyclura carinata.
BULLETIN FLORIDA STATE MUSEUM
creases in length and an annular impression is formed around its base.
After 2 (sometimes 3) skin sloughs, back spines begin development ex-
actly as for neck spines; back spines are therefore shorter, with two
fewer annuli than neck spines (most individuals). Relationship of
spines to sexual recognition and annuli to growth and age discussed
later. Back spines approach or even exceed neck spines in height in
some old lizards; annuli become inconspicuous as the spines become
smooth due to wear. Middorsal spines on anterior portion of the tail in
males also elongate with age, albeit very slowly. Maximum middorsal
scale height 18 mm in extremely old males. For other scale characters,
see Schwartz and Carey (1977).
CoLOR.-Exhibiting great individual and population color variabil-
ity. Patterns tend to be darker (gray, brown, or green, depending on
population) immediately following emergence and preceding
submergence each day. Midday coloration typically light gray to
bleached green (related to population). Changing albedo presumably is
an adaptation to increase absorptive radiation in suboptimal ambient
temperature regimes (Cowles and Bogert 1944). Color change most
rapid during the morning basking period, timed at less than one hour.
Relationships of changing albedo and skin reflectivity to ther-
moregulation under study (Auth, in preparation). Seasonal color
changes related to hormonal levels (see Carpenter 1967; Ferguson
1976) not evident.
Interpopulation color differences on Caicos bank very pronounced.
Lizards from eastern populations (Middleton and Long cays) drab gray
dorsally and ventrally with only slight differences in darkness of gray.
Fort George and Pine Cay lizards brownish to greenish-gray following
emergence, nearly white-gray at midday; venter gray to blue-gray.
Abrupt pigmentation change occurs between Pine Cay and Water Cay
(to the south); lizards from Water and Little Water cays most brillant-
ly colored of Caicos populations; basically dark gray-green on
emergence, pale yellow-green during basking; typically lighter venter
blue-gray, flushed with yellow. Yellow coloration extends over tail and
on ventral surfaces of limbs and digits. Pine and Water cays have ap-
parently been separated throughout historic time by a deep water
channel, allowing the maintenance of very different color morphs.
Also exhibiting variable pattern of narrow vertical stripes on
dorso-lateral body surface; stripes most obvious near anterior middor-
sal line, increasingly less apparent laterally and posteriorly; typically 9
or 10 stripes (i.e. areas where pigmentation simply lighter than adja-
cent regions). Pattern most obvious in hatchlings and juveniles;
typically obscure in adults.
ANATOMY.-Thyroid gland morphology discussed by Lynn et al.
(1966). Digestive tract anatomy discussed in Iverson (1980).
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
HABITAT
CLIMATE
The Turks and Caicos Islands experience a typical tropical
maritime climate. East-southeasterly tradewinds predominate and
average 25.9 km per hour throughout the year, and annual air
temperature fluctuations are not great (Fig. 8). Recorded annual air
temperature extremes between 1960 and 1968 on Grand Turk (110 km
to the east of the study island) were 15.6 C and 36.0 C. However,
microclimatic temperatures show much greater fluctuations both daily
and seasonally. Temperatures on light coral sand substrates ranged
from 12.5 C to 60.0 C on the study island; those on darker soils were
considerable higher. Substrate temperature differentials between ex-
posed and shaded areas were greatest during midday in July through
August with a maximum recorded difference of 25 C (31-56 C). Twenty
degree divergences are typical of summer days without midday
precipitation. The maximum recorded winter (November-December)
shaded-exposed substrate differential was 18.5 C.
To provide a general picture of the diurnal thermal environment,
microclimatic temperature data from optimum days (unaffected by
overcast or rainy conditions) on the study site were averaged by half
hour for two periods, representing the longest and shortest days of the
year (Fig. 9). Data from six days in late June 1974 and six in December
1973 were used. These differences in summer and winter temperatures
are in part due to an annual fluctuation in day length (photoperiod) of
nearly three hours. A more detailed analysis of the thermal environ-
ment and its relation to the biology of Cyclura carinata on Water Cay,
Caicos Islands, is found in Auth (ms).
Since it was possible for me to monitor rainfall only while on the
study island, data collected between 1900 and 1968 at the Grand Turk
Auxiliary Airfield (latitude 2126'N, longitude 71008'W; elevation 4
m) are presented here, unless otherwise indicated. A well-defined dry
season exists from January through May with monthly rainfall
averaging only 31.5 mm (Fig. 10). The wet season usually begins and
ends rather abruptly in June and January, respectively, and rainfall
averages 62.8 mm monthly. In addition to amount of rainfall, the
percentage of days per month experiencing some rainfall also increases
substantially during the wet season (Table 2). Average annual rainfall
on Grand Turk is 597 mm. However, based on 458 mm recorded on
Pine Cay in 194 days over three years, the annual estimate is approx-
imately 862 mm, somewhat higher than on Grand Turk. Comparison of
the vegetation, soil moisture, and general weather conditions across
the bank on several occasions, in addition to information supplied by
locals, indicate that rainfall is greater on the more western islands of
the bank, but probably does not exceed 760 mm annually.
1979
BULLETIN FLORIDA STATE MUSEUM
MAX SHADED
SUBSTRATE
MEAN DAILY MAX
MEAN AIRLY MIN
MIN AIR
J F IM
J F MA
-~ I I I
M J A S N
M J J A S O N D
FIGURE 8.-Average monthly temperature regime in Turks and Caicos Islands.
Substrate temperatures were recorded at SW Blind, Pine Cay, during study period; re-
maining temperatures collected between 1900 and 1968 at Grand Turk Airfield, Grand
Turk.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
TABLE 2.-MONTHLY FREQUENCY OF STUDY DAYS ON PINE CAY WITH PRECIPITATION.
Jan Feb Mar Apr May June
Percentage 0 -- 17.6 0 25 37.8
Days 4 17 12 12 37
Sampled
July Aug Sept Oct Nov Dec
Percentage 42.9 56.3 52.4 54.8 62.5 25
Days 28 16 21 31 16 20
Sampled
45 SUBSTRATE
IN
-40 SUN
-35
-30 SHADED SUBSTRATE
-25
U -20
DECEMBER
6 9 12 15 18
S-55
SUBSTRATE
U 50ININ
:: 5 CM
LU
45 U ABOVE
45 ABOVE
SUBSTRATE
IN SUN
-40
35
3 / SHADED SUBSTRATE
30
-25 25 CM BELOW GROUND
JUNE
5 6 7 8 9 10 11 12 13 14 15 16 17 18 EST
TIME of DAY
FIGURE 9.-Average diurnal microclimatic temperatures for June and December at SW
Blind study site. Data averaged by half hour for six storm-free days in June, and four in
December. Arrows indicate sunrise and sunset.
1979
BULLETIN FLORIDA STATE MUSEUM
Changes in rainfall, temperature, and photoperiod are the major
aspects of climatic seasonality. The effects of each of these are
reflected in lizard activity. Days are often cool enough to curtail lizard
activity in the winter, but almost never so in summer. The climate in
the western cays of the Caicos Islands is one of a warm dry spring
(March to May), followed by a hot, wet summer (June to October)
which grades into an even wetter, but still warm autumn (September
to December), and is followed by a cool, relatively dry winter (January
to March). Abrupt changes in temperature and precipitation
characterize the transition between the wet and dry seasons.
SOIL
Reflecting their reef origin, the Turks and Caicos Islands are
characterized by honeycomb limestone formations usually covered
with coral sand. The rocks are typically exposed along the windward
shores, with broad sandy beaches along the leeward. Inland accumula-
tions of humus provide a rich nutrient source and support more lux-
uriant vegetation (see Vegetation).
Iguanas frequent rocky and sandy areas as well as the more
elevated humus areas, but generally avoid the lower areas with thicker
100-
75-
E
S50
-J
Z 50-
I /^
FIGURE
Islands.
J F M A M J J A S O N D
10.-Average monthly rainfall, 1900-1968, at Grand Turk Airfield, Turks
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
soils due to the proximity of the water table to the surface and their in-
ability to dig through the root mass.
VEGETATION
The spatial relationships of the principal vegetation types on Pine
Cay are illustrated in Figure 11 and listed in Table 3. Community
distribution of most of the plants on Pine Cay is found in Auffenberg
(ms). The vegetation on Pine Cay corresponds to the "Evergreen
Bushland" of Beard (1949), and is physiognomically similar to that
found on Anegada in the British Virgin Islands by D'Arcy (1975). The
same genera (if not species) are represented in similar habitats on both
islands. Although D'Arcy (1975) divided the flora of Anegada into
only four primarily edaphic communities (shorelines, sandy plains,
limestone plains, and vegetation near man), it seems justified on Pine
Cay to distinguish additional plant communities within at least two of
his provinces. A more thorough discussion of the components of the
vegetation types on Pine Cay and their relationships appears in Auf-
fenberg (ms).
Cyclura carinata inhabited all of Pine Cay's plant communities ex-
cept the Marsh and portions of the Mixed Woodland vegetation types.
These are areas where the proximity of the water table to the ground
surface precluded the possibility of burrow construction and vegeta-
tion was too dense for movement. Cyclura reached its maximum adult
abundance on Pine Cay in areas of Rocky Coppice (Fig. 12). Young
lizards were more commonly observed in areas of Open (Fig. 13) and
Dense Scrub.
BURROWS
Unless natural shelters in the form of abandoned land crab (Car-
disoma guanhumi) burrows or honeycomb limestone or coral forma-
tions are available, Cyclura carinata digs its own burrows. Since
natural retreats are not abundant on the study islands, most lizards
dig their burrows. Large mounds of vegetation, dirt, and rocks piled up
by bulldozers while clearing roads were often used for retreats by
lizards on Pine Cay. These sites also offer excellent elevated basking
sites.
Adult male iguanas exhibit relatively great attachment of specific
burrows. This is reflected in the greater average length, depth, and
complexity of burrows dug by males versus those dug by females.
Mean burrow length for 8 females and 12 males from Pine and Water
cays was 3.09 0.96 m (range 1.83 to 5.02) and 4.39 1.53 m (1.37 to
6.40), respectively. Mean burrow depth, measured to the top of the
burrow terminus for these same lizards was 31.5 25.3 cm (range 12.7
to 91.4) and 69.1 42.9 cm (25.4 to 183.0 respectively). Sexual dif-
197
BULLETIN FLORIDA STATE MUSEUM
TABLE 3.-PRINCIPAL VEGETATION TYPES ON PINE CAY, CAICOS ISLANDS, BRITISH WEST
INDIES.
Vegetation Type
Dense Scrub
Mixed Woodland
Open Scrub
Beach or Rocky Coast
Marsh and Lakes
Airstrip and Hotel
Development
Rocky Coppice
Mesic Coppice
Area
(ha)
119.94
Percent
of Total
Area
34.41
69.37 19.90
47.24 13.55
42.01 12.05
26.33 7.55
17.85 5.12
15.31 4.39
10.53 3.02
Dominant Plants
Casasia clusiaefolia
Coccoloba uvifera
Erithalis fruticosa
Phialanthus myrtilloides
Thrinax microcarpa
Erithalis fruticosa
Metopium toxiferum
Pinus caribbaea
Psidium longipes
Reynosa septentrionalis
Antirhea myrtifolia
Coccoloba uvifera
Ernodea millspaughii
Psidium longipes
Strumpfia maritima
Beach Chamaesyce vaginulata
Ernodea millspaughii
Rachiallis americana
Scaevola plumierii
Strumpfia maritima
Rocky Coast Guapira obtusata
Manilkara bahamensis
Rachiallis americana
Strumpfia maritima
Zizyphus taylori
Conocarpus erectus
Mariscus jamaicensis
Antirhea myrtifolia
Coccoloba krugii
Eugenia foetida
Manilkara bahamensis
Metopium toxiferum
Pithecellobium guadelupense
Reynosa septentrionalis
Zizyphus taylori
Byrsonema lucida
Coccoloba uvifera
Erithalis fruticosa
Reynosa septentrionalis
Total 348.58 99.99
Vol. 24, No. 3
Total
348.58 99.99
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
ferences in burrow depth are also due, in part, to the need for shallow
incubating chambers for successful nesting in females; burrow length
differences are also related to sexual dimorphism in size. Though
adults of both sexes commonly use the same burrow, strongly ter-
ritorial adult males never share them, unless as a retreat after having
been frightened. Although territorial adult male lizards near the SW
Blind maintained a single retreat, they were nevertheless aware of all
burrows (and other potential retreats) both within their own territories
and within those of adjacent males.
Even subadult lizards showed familiarity with burrows far outside
their normal activity ranges. On 20 September 1973 near the Ridge
Area on Pine Cay, a 178 mm SVL lizard was removed from its burrow.
After marking, it was released at the site of its burrow. It ran directly
and non-stop 16.1 m, where it entered another active burrow. The se-
cond burrow was found to contain the marked lizard, in addition to its
resident male (SVL 229 mm). When released after marking, this resi-
dent immediately ran over the ridge and directly to the burrow first ex-
cavated. The lizards were clearly aware of the exact location of the
other's burrow.
Blocking of a territorial male's primary burrow caused him to shift
his retreat. Removal of the obstacle after one to three days was fol-
SROCKY COP........PICE
))
@ MIXED WOODLAND
O BEACH OR ROCKY COAST
FIGURE 11.-Principal zones of vegetation on Pine Cay, Caicos Islands (after Auf-
fenberg MS). Inland open areas represent lakes, airstrip, or hotel grounds (within
dashed lines).
BULLETIN FLORIDA STATE MUSEUM
lowed by his return to the primary burrow. The effect of permanent
destruction of the primary burrow was not determined. The short term
blockage seemed to cause no change in activity range, but it is
suspected that a shift may occur if the burrow is destroyed.
Juveniles and subadults frequently shift burrows. One subadult
non-territorial male, in the SW Blind area, carrying a transmitter,
utilized three different burrows on three consecutive nights. However,
in some areas the unavailability of auxiliary retreats necessitates the
continual use of a single site. A hatchling took up residence in a small
hollow tree limb in a brush pile on 1 September 1974 within only a few
days of emergence. It still occupied the site in April 1975 when last
observed. Thereafter it was not seen on the study site, and presumably
had been killed.
The following patterns in burrow usage were observed in the Ridge
Area. Large burrows active at the beginning of the study remained so
throughout the study period, but there was considerable turnover of
small burrows probably due to (1) predation on juveniles; (2) lack of
burrow fidelity in juveniles; and (3) periodic excavation of burrows by
terrestrial crabs. Since the burrow is central to all activity in Cyclura
carinata, its importance cannot be overemphasized.
Not surprisingly, burrow excavation in all species of Cyclura seems
to be related to the substrate conditions. In areas where sandy dune
situations predominate, as on the typically small, low islands of the
FIGURE 12.-Ecotone between typical Rocky Coppice (background) and Rocky Coast
habitats on Pine Cay.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
Bahaman archipelago, dug burrows are used. However, on islands
dominated by cavernicolous limestone and coral exposures, where
there is no possibility of burrow excavation by iguanas, natural
retreats are employed (see Retreats under ACTIVITY AND
MOVEMENTS).
The presence of at least some friable soil for nest construction ap-
pears to be a very important factor ultimately limiting distribution
and numbers of Cyclura populations. In the species of Cyclura for
which the nest site has been described (Noble 1923; Wiewandt 1977) a
nest burrow was excavated in well-insolated soil areas, sometimes
several km from the female's normal activity range (see Discussion
under REPRODUCTION). In addition to protection, burrows could
serve a thermoregulatory function; however, lizards do not use them as
heat sinks, even under extreme conditions.
Adult Cyclura typically maintain their burrows by removing sand,
leaves, and other debris during the middle of the day when general
lizard activity is reduced due to high environmental temperatures.
However, this is not a daily routine; a period of several days generally
separates burrow cleaning activities. In removing debris, the lizard
enters the burrow head first and kicks material backward as it moves
further inside. Emerging from the burrow head first, it turns and
repeats the procedure several times.
The complete excavation of a burrow was never observed; the time
required is unknown. However, a young adult male completely ex-
FIGURE 13.-Typical Open Scrub habitat on Pine Cay.
201
BULLETIN FLORIDA STATE MUSEUM
cavated a new burrow near the SW Blind during my absence between
20 July and 1 September 1974.
Neonate lizards usually use natural cavities or spaces cleared
beneath rocks, roots, logs, etc., for retreats. In open sandy areas, they
will excavate their own burrows. These burrows are usually shallow (<
15 cm deep) and short (< 50 cm), with diameters between 2.5 and 3 cm.
Some have short side branches but these may be added by crabs.
Since many young lizards frequent more than one burrow and
many small burrows are actively maintained by crabs, small burrows
are not useful in estimating lizard density. Data concerning locations
of large active burrows can, however, provide fairly accurate estimates
of adult lizard density (see DENSITY AND DEMOGRAPHY).
Burrow dimensions and complexity are quite variable (Fig. 14),
dependent in part on the surface and subsurface soil texture. The
longest burrow excavated was in dune sand on Pine Cay and measured
6.4 m. It was occupied by both a female and a male when opened. One
of the biggest burrows encountered was an active one which I could
not completely excavate. The burrow was in an area of deep dune sand
nearly devoid of vegetation. The 16 cm diameter of the burrow sug-
gested that it had been dug by a male. Beyond 5.0 m of horizontal ex-
cavation, the burrow was 1.5 m below the sand surface. It continued
downward with the same slope at least 1 m farther. Digging was
suspended due to constant collapsing of the excavation pit.
Burrow orientation on Pine and Water cays (Fig. 15), appears to be
related more to micro-topographic features than to intentional direc-
tional construction. More burrows generally open to the northwest and
southeast on these two islands, because these retreats lie perpen-
dicular to the generally northeast-to-southwest lying ridges (Figs. 3
and 14). Cyclura prefers digging under the limestone exposures in the
sides of these ridges to digging in open flat sandy areas. In the latter
areas, burrows are typically excavated into the sides of small hum-
mocks formed by the accumulation of blown sand around the bases of
clumps of vegetation. An obvious advantage in avoiding flat areas of
open sand for burrow construction is the reduction of the possibility of
entombment by burrow collapse.
As in the burrows of the Florida gopher tortoise Gopherus poly-
phemus (Young and Goff 1939), there are numerous arthropod in-
quilines in nearly every Cyclura burrow, many apparently obligatory.
The most common and seemingly most obligatory were camel crickets
(Amphiacusta sp.). Also found were solpugids (genus Ammotrechella),
scorpionids, amblypygids (Tarantula marginepennis), nymphal
cicadas (Ollanta caicosensis), and numerous unidentified spiders.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
60 13
F 13 3
15 15
1M
25
90
25
20
FIGURE 14.-Variation in burrow morphology and orientation in adult Cyclura carinata.
Soil depth (in cm) to top of burrow is indicated; changes in depth are uniform between
measurements. Letters adjacent to burrow entrance (solid circles) indicate sex of in-
habitant. Asterisks mark burrows used for nesting in previous years.
1979
BULLETIN FLORIDA STATE MUSEUM
REPRODUCTION
MALE SEXUAL CYCLE
The male testicular cycle closely parallels the female reproductive
cycle. Since testes weight has been shown to be an accurate indicator
of testicular activity in lizards (Hahn 1964; Marshall and Hook 1960;
Ballinger 1973), no histological analysis was made. Testes reach max-
imum sizes in April and May, declining rapidly in June and July to
maximum regression in early fall (Table 4). Testicular size maxima are
coincident with breeding in Cyclura carinata. A similar cycle (early
spring maxima and late summer minima) is typical of at least the igua-
nid lizards.
Sexual maturity in male C. carinata was determined by testicular
enlargement between January and June, or actual observation of at
FIGURE 15.-Orientation of burrow entrances in Cyclura carinata, recorded as compass
direction into burrow.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
TABLE 4.-SEASONAL VARIATION IN PROPORTIONAL TESTES WEIGHT (TESTES WEIGHT IN
GM X 10-/SVL IN MM) IN MALE Cyclura carinata OVER 216 MM SVL.
Sample
Date N X S.D. Range
March 6 1 867
May 10 1 1358 -
June 30 7 178 141.13 48-454
August 15 2 117 70-164
September 15 1 47 -
December 15 2 177 151-203
December 30 4 165.5 115.37 62-305
tempted or successful matings in May. The smallest male with en-
larged testes was 216 mm SVL (weight approximately 440 gm). The
largest males without testicular enlargement were 222 mm SVL (435
gm live weight) and 210 mm SVL (365 gm). A 219 mm SVL captive
male, which attempted copulations on numerous occasions during
May 1975, was the smallest male observed to exhibit courtship
behavior. These data indicate that sexual maturity in males is reached
at approximately 220 mm SVL and a body weight of 375 to 475 gm.
Growth data indicate this requires about seven years (see GROWTH).
Adult males averaged 276.3 mm SVL (191-360) and 935.1 gm body
weight (256-1864).
FEMALE SEXUAL CYCLE
Ovaries are difficult to distinguish from testes in lizards less than
one year of age; however, the obvious presence of oviducts in females
allows accurate sexing of even hatchlings. Immature ovaries contain
numerous follicles up to 4 mm in diameter. Maximum follicular
diameter in mature females between oviposition and spring
recrudescence is also approximately 4 mm (Fig. 16). Yolking of follicles
begins between 1 January and 1 March and continues until ovulation
in early May. Maximum follicular diameters reach 30 mm at that time.
Seasonal combined ovarian weights reflect the same trends as
follicular diameters (Fig. 17), with ovarian weight maxima (63.7 gm in
a 248 mm SVL lizard with five enlarged follicles) in mature females oc-
curring in early May and post-reproductive minima (generally less
than 0.35 gm) from July through December. The maximum combined
ovarian weight recorded in an immature (184 mm SVL) female was
0.275 gm in March. Immature weights were normally considerably
less than this. Perhaps her ovaries were developing in preparation for
breeding the following year when she would surely have been of adult
size.
BULLETIN FLORIDA STATE MUSEUM
Oviducal eggs were not present before at least the last of April and
were noted only as late as 9 June. Yolked follicles and oviducal eggs
were never found in the same female and no yolked follicles (except an
occasional atretic one) were found in post-ovipository females. Fresh
corpora hemoragica averaged 6 mm in diameter, but regression was
rapid and corpora lutea were usually unidentifiable by early
September (Fig. 18).
Of only two females with oviducal eggs, one showed evidence of
transuterine migration of ova. The right reproductive tract of that
female included two corpora lutea in the ovary and three eggs in the
oviduct; the left tract bore four corpora lutea and three oviducal eggs.
Cuellar (1970) has previously discussed this phenomenon in lizards.
Minimum sizes for mature females (as indicated by the presence of
yolked ovarian follicles, oviducal eggs or corpora lutea) were 184 mm
SVL (250 gm; with enlarged yolked follicles), 190 mm SVL (280 gm;
M N
30o EGG DIAMETER
S F' M A M J J A S 0 N D
FIGURE 16.-Seasonal variation in maximum follicle diameter (mm) in ovaries of female
Cyclura carinata. Small dots indicate individual females; large dots, two or more
lizards. M and N mark mating and nesting seasons, respectively.
Vol. 24, No. 3
*
* *
T ..
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
corpora lutea present), 194 mm SVL (live weight unknown; with cor-
pora lutea), and 197 mm SVL (205 gm; with corpora lutea). Maturity of
young adult and subadult females collected between September and
January could not be accurately determined due to the regressed state
of the ovaries even in obviously adult females. The largest immature
females collected between January and August were 210 mm SVL (ap-
proximately 320 gm), 191 mm SVL (240 gm), and 184 mm SVL (weight
1601 2567
&1485
140.
120-
I-
z
2 100-
LU
z
< 80-
-s
Z
t 60-
0
o
i
0s
.4
4* b
0^
J F M A M J J A S O N D
FIGURE 17.-Seasonal changes in proportional ovarian weight (grams x 10"'/SVL in
mm) in mature female Cyclura carinata. Each point represents one individual lizard.
1979
BULLETIN FLORIDA STATE MUSEUM
unknown). Maturity in females at 185-200 mm SVL (200-300 gm) at an
age of about six years (see GROWTH) is indicated. Nearly all females
presumably oviposit their first clutch of eggs between age six and
seven. Adult females averaged 225.4 mm SVL (190-292) and 475.6 gm
(205-1135) body weight.
COURTSHIP AND MATING
From late March through April males became increasingly in-
terested in females. During April males were frequently observed
following females on the ground. At this time, the resident territory-
holding male typically approached within 1 m of the female, but did
not display or otherwise court the female. The approach usually caused
the female to headbob (submissively; see SOCIAL
ORGANIZATION), move a short distance away, stop, and again bob
to the male. The male often reciprocated with a headbob, and again ap-
proached the female closely and the sequence was repeated (up to 12
times). The impression was that the male was attempting to insure his
proximity to a female as the mating season approached. Perhaps this
precourtship interest is necessary for the induction of receptivity as in
6- *
5-
*E*
4- *
3-
ZE
*
1-
I l I I i I I l I I I II I
1 8 15 22 29 6 13 20 27 3 10 17 24 31 7 14 21
JUNE JULY AUG SEPT
FIGURE 18.-Regression of ovarian corpora lutea in Cyclura carinata following oviposi-
tion. Maximum diameter is plotted.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
Drosophila melanogaster (see Parker 1974:158) and Anolis carolinen-
sis (Crews 1975b).
Resident males terminated their female-directed activity to
displace neighboring males from their (the resident's) territory (hence
away from the female) at this time of the year, just as they did during
the remainder of the year. However, it was my subjective opinion that
the males were more willing to defend at this time of the year than at
any other. There was no question that the general level of activity was
greatest at this time of the year (see ACTIVITY and MOVEMENTS).
Following defense, the resident male returned to the female and re-
sumed his interest in her.
In some cases, the male was so persistent in his attempts to closely
approach the female, that she ultimately moved out of his territory
and into that of a neighboring male. However, females sometimes also
moved between males' territories without this pressure from the resi-
dent males. Perhaps female Cyclura were making active choices among
courting partners at this time, as Trivers (1976) suggested for Anolis
garmani.
The interest of males in females increased through April,
presumably until the female tolerated the close approach of a male and
active courtship could proceed. Unfortunately, neither active court-
ship nor copulation was observed in nature. However, they were fre-
quently observed in captivity and the basic behavioral components are
undoubtedly the same as those in non-captives.
Courtship was observed nearly 100 times (three times to comple-
tion) in the captive enclosure in Gainesville during nine days between
24 April and 9 May 1975 (Table 5). During this period, four mature
females and at least two of four males were confined in a pen at any one
time. The lizards were captured 5-9 April 1975 on the study islands.
TABLE 5.-AVERAGE NUMBER OF COURTSHIPS PER DAY ATTEMPTED BY EACH MALE
WITH EACH FEMALE IN GAINESVILLE ENCLOSURE DURING NINE DAYS BE-
TWEEN 24 APRIL AND 9 MAY 1975.
MALES
#1 #3 #4
SVL
FEMALES' (mm) 349 286 219
#1 235 3.0 2.333 4.75
#2 235 1.67 1.222 0
#3 216 1.33 1.222 0.75
#4 185 1.000 0.75
Days male
present 3
'All females were present everyday.
9 4
1979
209
BULLETIN FLORIDA STATE MUSEUM
Courtship Ethoqram
Display
Approach
(with or
without bob)
Vibratory Phase
(while approaching?)
Straddle and neck bite
Release neck hold -
Dragging phase
Tail Maneuver
_ Bob
-(submissive; on s approach
Complete rejection
(moves away)
Maintain position
Rejection
(runs away; usually with ope
Smoothed bobs)
Maintain position
"Return bite
SEscape reaction
(with open-mouthed bobs)
Refusal to arch tail
(possible only if small)
Tail arch
(Acceptance)
Opposition of cloacae
'INTROMISSION
Withdrawal
S'-Tail Wiggle
TERMINATION OF MATING
FIGURE 19.-Behavioral components of courtship in Cyclura carinata.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
The females and smallest male (#4) were released into the captive
enclosure on 17 April, while the other males were maintained separate-
ly in the laboratory. These males were introduced into the pen at
various times between 24 April and 9 May to investigate dominance
relationships (see SOCIAL ORGANIZATION).
Successful mating behavior can be divided into four basic stages:
approaching, displaying, neck holding, and copulating. Figure 19 il-
lustrates the male and female components of courtship behavior.
APPROACH.-In captivity the male and female did not always ex-
change headbobs prior to the male's approach to the female. In the
field, the female always bobbed submissively at the appearance of the
male; the male often did not reciprocate (see SOCIAL ORGANIZA-
TION). The courting male typically approached the female laterally
and from behind (their bodies aligned at approximately a 30 to 450
angle). The profile of the approaching male once within 0.5 m of the
female was very low to the ground. The body was dorsoventrally flat-
tened and the chin was kept less than 5 cm from the substrate. A few
times the male turned his head to inspect the female's hip area, but
usually approached until his head was lateral to her anterior trunk
region. At this point the female often moved away, rejecting the
male's advances. If she did not (or could not, as in some captive situa-
tions) the male began his courtship display and continued to approach
the female.
DISPLAY OR VIBRATORY PHASE.-The courtship display of Cyclura
carinata was stereotyped and very similar to that of most other igua-
nid and agamid lizards that have been studied (Carpenter 1967; Gon-
zales 1974). The male continued his approach toward the female while
rapidly vibrating his head vertically. I have termed this behavior
vibratoryy" display due to the low amplitude of the headbobs. A
typical display action pattern (DAP; see Carpenter and Grubitz 1961)
of this head movement appears in Figure 20. Four videotaped
displays, each including four oscillations of the head, averaged 0.36
seconds (0.32-0.40). Males sometimes performed displays with open
mouths.
This vibratory courtship display is synonymous with the
"jiggling" display described by Evans (1938) and Ruibal (1967), the
"courtship nod" by Carpenter (1962b), and the "shudder sequence" by
Ferguson (1970) for other lizards. In each case, the display consisted of
a sequence of shallow, rapid headbobs. Male Ctenosaura pectinata
(Evans 1951) and Amblyrhynchus cristatus (Carpenter 1966) also ex-
hibit a similar courtship display. Sauromalus obesus (Berry 1974) is
the only iguanine lizard studied to date that lacks this display.
Females rejected male courtship advances by a stereotyped rejec-
BULLETIN FLORIDA STATE MUSEUM
tion display or by simply running away. Either behavior was accom-
panied by vigorous headbobbing, typically with an open mouth. In the
rejection display (Fig. 21), the female compressed her body laterally,
postured high on all four legs with her back strongly arched and her
tail on the ground, and headbobbed rapidly. In the field, as in many of
the captive courtships, this display is probably sufficient to thwart the
male's courting interests. However, captive males often continued the
courtship sequence despite this display. If the female maintained her
position during the male's vibratory display and approach, the male
terminated the display, raised up and gripped the female's neck in his
teeth.
Many iguanid lizard species have a similar rejection posture (Fitch
1956; Clarke 1963; Carpenter 1967). Noble and Bradley (1933) first
described and illustrated this behavior but were unable to determine
its significance. Within the subfamily Iguaninae, Sauromalus obesus
(Berry 1974) also uses this rejection posture, while Amblyrhynchus
cristatus apparently does not (Carpenter 1967); other members have
not been sufficiently studied.
Only one homosexual courtship (with the smallest male) was
observed and it was terminated by the courting male following his
vibratory display.
NECK HOLDING.-Following the vibratory phase of courtship, the
male moved to straddle the female and secure a mouth grip on the dor-
sal region of the female's neck. The female could still terminate the
LU
CL
-_
TIME
FIGURE 20.-Display action pattern of typical vibratory courtship display of a male
Cyclura carinata. Time increments are 0.03 second. Amplitude is proportional to the
distance from the lizard's eye to the substrate. Graph is accurate to 0.015 second.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
courtship at this point by turning and biting at the male's head and/or
struggling free. Females sometimes attempted to walk away, dragging
the male for short distances.
Once the female's neck was securely held, the male attempted to
maneuver his tail under that of the female to align their cloacae. The
receptive female then arched her tail upward to facilitate the male's
tail maneuvering. She could apparently still reject the male's ad-
vances, by refusing to arch her tail only if the courting male was
smaller than herself; large males could force their tails under the
female's tail even if she did not arch it. This was observed once in cap-
tivity during the forced copulation (rape) of one of the females (dis-
cussed later) by a large male. The refusal of a female to arch her tail to
allow cloacal apposition was observed six times when a small male (219
mm SVL) had obtained a neck grip on a larger female. Once the cloacae
were finally opposed, the neck grip was maintained until hemipenial
withdrawal following copulation. The mating posture was exactly like
that pictured for Amblyrhynchus by Schmidt (1935).
COPULATION.-Once the cloacae were opposed, intromission fol-
lowed immediately and lasted from 40 to 76 seconds (X = 58.7, N = 3).
No thrusting by the male was observed. Wiggling of the distal portion
of the female's tail immediately preceded withdrawal of the hemipenis.
Uncoupling was rapid; the male released his neck grip and backed
away from the female. His pelvis remained elevated from the ground
until his hemipenis was fully retracted. Typically both lizards then
moved very little and rested quietly. Their activity during the re-
mainder of the day was generally depressed.
In all iguanine lizards, except Iguana iguana, for which data are
available (Table 6), copulation (i.e. female receptivity) occurs approx-
imately one month before oviposition. A distinct relationship with the
female ovarian cycle is implied. It is suggested, but not known, that
receptivity in Cyclura carinata immediately precedes ovulation as it
FIGURE 21.-Rejection posture of female Cyclura carinata.
1979
AVERAGE
MAXIMUM MAXIMUM ADULT AVERAGE AVERAGE AVERAGE EGG
SIZE WEIGHT SIZE WEIGHT CLUTCH EGG SIZE WEIGHT
(mm SVL) (kg) (mm SVL) (kg) SIZE (mm) (gm)
Amblyrhynchus Galapagos
cristatus
Galapagos
(Narborough)
Galapagos
(Hood)
Galapagos
(Narborough)
Galapagos
Galapagos
Galapagos
(Santa Cruz)
Brachylophus Fiji Islands
fasciatus
Fiji Islands
Conolophus
pallidus
3.118
o'=400 o'=2.948 o'=361 o'=2.01
cr=430
9 =350
o,=510
9 =350
o'=2.580 o'=341 o'=1.984 2.29 93 x 42
9 =1.928 9 =290 9 =0.992 (2-3)
9 =268 3n 86.0 x 42.5
80-120 t
z
96.3 5
(79-121) 2
82.0
(80.2-83.8) >
-
C0
3-4 40 x 30
Galapagos
(Barrington)
Galapagos
(Barrington)
Galapagos
Conolophus Galapagos
subcristatus (South Plazas)
o=420 cr=3.260
9 =380 9 =2.410
- 5 19 x 13
(n=3)
- 7,10 50-57 x
73-82
7-10 64 x 35
1.8-2.1 -
350 1.700* -
0,
Co
TABLE 6.-REPRODUCTIVE DATA FOR THE LIZARD SUBFAMILY IGUANINAE.
SPECIES
LOCATION
TABLE 6.-EXTENDED.
HATCHLING HATCHLING
INCUBATION SIZE WEIGHT BREEDING NESTING HATCHING
TIME (mm SVL) (gm) SEASON SEASON SEASON SOURCE
Eibl-Eibesfeldt 1961
Feb. 3-4 Bartholomew 1966
-- Jan.-Mar. early April early July Carpenter 1966
ca. 2 m Dec.-Jan. late Jan.- April- Carpenter 1966
Feb. May
112-113 d 97.0 58.7 before Feb. June Shaw 1966
(captive) 24 (captive)
S- February May DeVries 1974
105-130 ca. 80-120 Feb.-early early May- Bartholomew et al. 1976
March early June
17-23 w 65 -- Cogger 1974
(captive)
Sept.-Mar. Nov.-March Cahill 1970; Bustard 1970a
(captive) (captive)
Oct.-Nov.? Van Denburgh & Slevin 1913
- Dec.-Jan? Slevin 1935
..- Wilhoft 1958
--- Carpenter 1969
TABLE 6.-CONTINUED.
Conolophus sp. Galapagos -
Ctenosaura Veracruz, 17, 17, 30-35 x
acanthura Mexico 28 15-20
Ctenosaura Sonora, 9=179+ 9=0.215+ 15n 25.5 x 12.8 4.67
hemilopha Mexico
Ctenosaura Morelos, 0c=320 = 1.000 49n 5.10*
pectinata Mexico 9 =325 9 =0.950
Morelos, -
Mexico
Guerrero, -
Mexico
Michoacan, -
Mexico
Tamaulipas, 9 =191+ 9 =0.315+ 17n 28.0 x 18.0 4.41
Mexico
Ctenosaura Yucatan -
similis
Yucatan, Nicaragua, 9=335+ 9 =306 -
Costa Rica
Chiapas, 20-30 -
Mexico
Belize -
Western Costa c =440 =415 21-34 24-34 x
Rica 9 =335 18-19
Western Costa 9 =350 9=298 54.9 27.8 x 19.1 -
Rica (34-87)
Nicaragua, Costa o0=489 o= 345 o'=1.034 43.4
Rica 9 =347 9=276 9=0.651
TABLE 6.-EXTENDED.
May-July
- early May*
early May
April 11
early
spring
Oct.-Nov. DeVries 1974
Smith & Burger 1950
Iverson, unpubl. data
Evans 1951
July Davis & Smith 1953
May-June Davis & Dixon 1961
early July Duellman 1961
Iverson, unpubl. data
June-July Duellman 1965
early June Fitch 1970
June- Alvarez del Toro 1972
August
June-July Henderson 1973
late April Fitch 1973b
-June
Hackforth-Jones (MS)
June Fitch & Henderson (MS)
54.0
(49-59)
90 d
<90 d
2.5 m
53-61
57
summer?
February
March-May
Nov.?-Feb.
April
late March-
early April
TABLE 6.-CONTINUED.
Cyclura Caicos Islands,
carinata BWI
o0=360 o'=1.864 0c=276 o0=0.935 4.65 51.8 x 31.1
9 =292 9=1.135 9 =225 9 =0.476 (2-9)
Cyclura Jamaica 490+ -
collei
Jamaica 20n -
Cyclura Dominican 17n -
20n 85 x 38
- 11-23 68.6 x 45.9
N=3
12n 78 x 47
o =545
9 =510
0=545
9 =510
c=6.80 o'=517 o'=6.10 12 80.3 x 50.9
9=5.40 9 =475 9 =4.70 (6-19)
13n -
C
r
--r
z
-1
77.7
O
(58.5-88.3) O
-
104.0
(82-159)
0
C.
Republic
Captive (?)
Hispaniola
Mona Island
Mona Island
Dominican
Republic
Dominican
Republic
Cyclura nr. Great Exuma, 290 7n -
cychlura Exumas,
Bahamas
Guana Cay, 3-4 -
Exumas
Guana Cay, c=355 o =1.40 o =303 a0=0.770 -
Exumas 9=320 9 =0.85 9 =283 9 =0.595
cornuta
25.9
(19.0-29.9)
0r=6.24
9 =4.76 9 =476
TABLE 6.-EXTENDED.
90 d 79.8 14.6 late April early June early This study
(76-83) (12.5-15.0) -early May September
Grant 1940a
April-May Lewis 1944, 1946
9 w? Nhl 1 92
June
July 5
July 31,
Aug. 4,
Aug. 11
(captive)
July*
mid July-
early Aug.
November 9
late Nov.-
early Dec.
(captive)
mi
late
Haast 1969
Shaw 1969
- Thomas in Carey 1975
id to Wiewandt, in prep.
Oct.
- Iverson, unpubl. data
- Wiewandt and Gicca,
unpubl. data
- Carey 1975
- Coenen in Carey 1975
- Windrow 1977
127 d
106-129 d
(captive)
82.6 d
(78-89)
54.1
(47.4-61.9)
101.3
(95-104)
119
(105-127)
74.0
(60-92)
early June
I
TABLE 6.-CONTINUED.
Cyclura Little Cayman 9 =420+ 8-20 -
nubila
Cuba 16n 76 x 44.5
Cuba 17n 65.6 x 44.5
Cyclura Anegada, British o =550 o =7.75 r =534 o =6.72 12-16 -
pinguis Virgin Islands 9 =500 9 =5.25 9 =468 9 =4.75
Cyclura Dominican 9 =340 4.67 -
ricordi Republic (4-6)
N=3
Dominican 460 3.18 354 1.74 -
Republic
Cyclura San Salvador, 5n -
rileyi Bahamas
Dipsosaurus California
dorsalis
California
California,
Arizona, &
Nevada
California
Arizona
Captive
o'=145
9=142
144
o'=127
9=120
9 = 107.3
5-6 28.0 x 16.8
N=2
3-8
3-5 26.4 x 15.0
4.44
(4-5)
March
June
(captive)
August?
April -
early May
May early
June
June 23
July 10
(captive)
April-June?
Aug. 11
(captive)
late June -
early July?
- early June -
mid August
June?
Sep
No0
- Grant 1940b
it. 24 Street 1952
v. 5-9 Shaw 1954
(captive)
Aug.-Sept.
Carey 1975
Carey 1975
Wiewandt and Gicca,
unpubl. data
Stejneger 1903
Smith 1946
Shaw 1952
August Norris 1953
August
Mayhew 1971
Parker 1972
Muth 1977
TABLE 6.-EXTENDED.
93 d
119-123 d
102.4
(95-110)
100?
54.73
[48-59)
43.4 d
(43-45)
47-52
47.4
(46-50)
4.62
(3.6-5.1)
TABLE 6.-CONTINUED.
Enyaliosaurus Michoacan, 154 0=147 -- -
clarki Mexico 9 =135
Michoacan, o'=165+ o0=0.200 0a=153 ou=0.131 7.5
Mexico 9=150+ 9 =0.150 9 =142 9 =0.108 (4-11)
N=6
TIuana T. eward 47.6 x 28.6
delicatissima
Islands
Lesser
Antilles
Iguana Panama
iguana
British Guiana
0o=345
9=346
22
(17-27)
ca. 35
- 32.25 41.3 x 22.2
(21-43)
N=4
- 4-7
N=2
- 20-70
Panama
Nicaragua
Eastern Costa
Rica
Columbia
- 9 =353
ca. 30
41n
35.3 38.0 x 26.2
(29-40)
N=7
41n 39 x 26
- 33-45
N=2
38n
25-60
-
-
-1
--
3
o
>
- nc
01
Panama
Captive
Chiapas,
Mexico
z
0
0
.o
m
c!
t-
Duellman & Duellman 1959
Iverson, unpubl. data
- Garman 1888
Aug.-Oct.?
-Feb.-March
Oct.-Nov. early Feb.
March
eggs found
April 4
March-
February
(captive)
Oct.-Dec.
early April
March 1
(captive)
late Jan.-
early Mar.
April 19
(captive)
March-
April
Dec.-
Feb.?
Lazell 1973
Hallinan 1920
Beebe 1944
June? Swanson 1950
Carr 1953
June 6 Hirth 1963
May 18
(captive)
late April-
early May
July 3
(captive)
June-Aug.
Licht & Moberly 1965
Rand 1968
Van Aperen 1969
Alvarez del Toro 1972
TABLE 6.-EXTENDED.
ca. 46
April?
early to
midJune
ca. 3 m
ca. 3 m
73 d @ 30C
65 d
(captive)
90 d
10.25
254 (total
length)
TABLE 6.-CONTINUED.
Panama
Colombia
Panama
Western Costa
Rica
Nicaragua
California
California
Arizona
California
California
California
Arizona
o0=420
o =3.20 9=280 9=1.10 14-70
32-39 x
24-27
o0=530 -
9 =390
o0=550 o0=2.60+ o0=361 o= 1.309 30.5 -
9 =411 9=2.15 9 =327 9 = 1.195 (11-54)
8-10 35.3 x 21.6
o0=197
9 =185
0o=220
9 =205
o0=203
9=184+
0o=207
9 =207
5n 38.25-40.0 x
21.6-24.75
o0=0.315 150-160 9 =0.05- 7n -
9 =0.255 0.25
150-220 7.8 -
(6-13)
170 0o=0.250 10n -
9=0.175
o0=176 6-10 28 x 14
9 =189 (oviducal)
13.0
(12.4-14.0) m
ci
--
z
--
10.28
C
O
----
5
>
t
3
C-
C.
41 x 23
(in nests)
NOTE: Asterisks indicate values extrapolated or interpolated from cited source. All species probably lay at most a single clutch per year. Values in parentheses are ranges. Sample sizes
for clutch size included where small, except where N = 1 (marked with n). Incubation times in days (d), weeks (w), or months (m).
o
Sauromalus
obesus
TAHLE 6.-EXTENDED.
ca. 3 m
100 d
@ 28C
168-171 d
(captive)
85 d
68 (260
total)
60 (253
total)
73-76?
60?
68-70?
46-60
May-June
March 26-
June 25?
Mar.-
April
May-June
64.6
(53.9-79.6)
February
March
late Feb.-
early Mar.
Jan.-Feb.
Feb.-Mar.
late May
late June*
June 22
May-June
late April- Rand 1972
May
late May Mueller 1972
mid-June Ricklefs & Cullen 1973
(captive)
mid-Dec.- Fitch 1973
early May
April- Fitch & Henderson 1977b
June
Shaw 1945, 1952
Smith 1946
Sept.* Gates 1957
Johnson 1965
Sept.? Berry 1974
Iverson, unpubl. data
August Prieto and Sorenson 1977
BULLETIN FLORIDA STATE MUSEUM
does in Anolis carolinensis (Crews 1973a), and perhaps Crotaphytus
wislizeni (Parker and Pianka 1976).
It is strongly suspected that female receptivity is terminated by
copulation, as Crews (1973b) has shown to be the case in Anolis
carolinensis. One captive female mated twice with the same male in
three days, but she was an unwilling partner in the second mating. The
male was able to "rape" the female due to his much larger size (286
mm SVL versus 235 mm) and the confinement of the enclosure. Since
no female Cyclura was observed to accept a male more than once in
captivity (mated females always rejected further courtship attempts),
I suspect that females copulate only once, with only one male, during
each breeding season.
Males, however, will copulate more than once during the breeding
season, but apparently only once during any one day. On 24 April,
male #3 had attempted to mate once (with another female) before he
copulated successfully with female #1. He did not attempt courtship
again that day. He courted unsuccessfully 3 times on the following
day, and on the next day 11 times (with two females) before he forcibly
mated #1 female. He did not try to court again that day, but did on
several following days. On 9 May, #3 male copulated successfully with
the first female (#3) he courted. She was very receptive and moved to
him immediately after his morning emergence. He did not attempt
courtship for the remainder of the day. It is suggested that males in
the field are able to mate with more than one female if they are
available.
In captivity, female #1 accepted male #3 on 24 April, and was raped
(by the same male) on 26 April; female # 3 accepted male #3 on 9 May.
The other two females were not observed to accept males, but both
later nested. It is therefore presumed that they also mated. The
earliest courtship attempt was observed on 24 April; none was attemp-
ted in two days of observation prior to that. Since the lizards involved
were captured less than three weeks prior to that time, a two to three
week mating season, centered about the first of May, is indicated.
POST-COPULATORY BEHAVIOR.-Captive males frequently dragged
their cloacal regions on the substrate both prior to and following court-
ship behavior. Two captive males also exhibited a strange modification
of normal defecatory behavior during the breeding season. The pelvic
region was elevated above the ground in typical defecation posture;
however, the abdominal contractions necessary to egest the fecal pellet
resulted in version of the hemipenes. The organs remained everted un-
til after the scat was deposited. As they were then withdrawn a small
quantity of white viscous fluid (semen?) dripped from the region of
each retracting hemipenis. I could not determine the significance of
this behavior.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
Probably the most significant post-copulatory behavior noted in
the captive situation was when the male drove off males that courted
the female with which he had copulated. This behavior was clearly
observed after only one of the three captive matings. Following the
other two copulations, other males did not attempt to court the mated
female.
Two other males were present in the enclosure at 1237 hours on 26
April 1975 when male #3 copulated with female #1. Male #2 was old,
senile, and subordinate to #3; he was never observed to court. Male #4
was young (first or second year post-maturity); he courted frequently
(Table 5) but was never accepted by a female.
Approximately 8 min after #3's copulation, male #4 courted female
#4 twice in less than 30 sec and was rejected each time following the
vibratory display. Male #3, resting in the shade, showed no interest in
this activity. However, at 1249 hr, #4 approached female #1 very
rapidly and after an abbreviated vibratory display, jumped up and bit
at her neck. Simultaneous with her attempts to reject him, #3 postured
(see SOCIAL ORGANIZATION), charged from his resting place, and
chased #4 away from "his" female. Following the short chase, #4
bobbed submissively, as #3 moved back to his resting place. Within 30
sec, #4 again moved to court #1 and again #3 postured, charged, and
drove #4 from the vicinity of the female, and then moved into the
shade to rest. This same sequence was repeated five times over the
following 5 min; 20 to 60 sec separated each sequence. At that time
(about 1256 hr), male #2 moved to the feeding station and this seemed
to stifle #4's advances temporarily.
No interaction occurred until 1321 hr when #4 resumed his courting
interest in #1, and #3 again chased him away from her. The sequence
was repeated six more times, each separated by 60 to 150 sec, over the
next 9 min. Male #4 dragged his cloaca on the substrate three times
during the following 9 min and retreated to a burrow for the remainder
of the day at 1341 hr. Number 3 male did not attempt to "guard" any
female during any other day of observation. This protective behavior
thus appears to be restricted to the day of copulation.
Assuming females are receptive for only a short time during the
ovarian cycle, the practice of guarding a recently-copulated female by
a male in the field would help guarantee that he, alone, contributed to
that female's entire brood that year. Parker (1974) has discussed the
significance of this behavior in his theoretical treatment of female-
guarding as a male time-investment strategy.
The mating system of Cyclura carinata is apparently one of serial
polygyny, with monogamy among some males (see Wilson 1975).
There appears to be pair-formation during at least the breeding season.
1979
BULLETIN FLORIDA STATE MUSEUM
Two females at the SW Blind lived within the home range of the same
respective males for two years until all were killed by dogs and cats.
Monogamy and/or polygyny seem to be the predominant systems
among the iguanines. Although no breeding observations were made,
pair bonding and monogamy have been suggested for Cyclura pinguis
(Carey 1975). Johnson (1965) noted male-female pairing in Sauromalus
obesus, but did not observe courtship. In a more complete behavioral
study, Berry (1974) found a polygynous system with pair formation for
the same species.
Male Mona Island Cyclura cornuta are generally polygynous but
some are apparently promiscuous; females are monogamous, polyan-
drous, or promiscuous (Wiewandt 1977). Street (1952) implied that
Cyclura nubila is promiscuous, but no supporting data were presented.
His observations were based on tame, unrestrained lizards inhabiting
a golf course in Cuba, but may not be representative of field popula-
tions. Alvarez del Toro's (1972) observations of Iguana iguana suggest
a polygynous mating system for the species. However, Peracca (1891,
cited in Noble and Bradley 1933) observed that captive male iguanas
mated with more than one female, but did so more with one female
than another. He also noted multiple insemination of females (up to 11
times). This suggests a polygamous if not totally promiscuous system,
but it may have been an artifact of the captive situation. Mueller
(1972) reported that the species is polygamous in Colombia. Further
studies of courtship behavior as well as all aspects of social behavior
are sorely needed for lizards of this subfamily if meaningful com-
parisons are to be made.
NESTING
Female Cyclura carinata oviposit their single annual clutch in early
June. Two gravid Pine Cay females had fully shelled oviducal eggs on
3 and 9 June and four recently deposited nests were excavated on 5
June, 7 June, and 9 June (2) on Pine and Water cays. A female at the
SW Blind site laid her eggs 6 June. A female captured 5 June on Water
Cay nested in an observation pen four days later. Captive lizards tend-
ed to nest later than native lizards, perhaps due to subnatural thermal
or photoperiod regimes. A Pine Cay female collected 4 April deposited
her clutch on 12 June in Gainesville. A Water Cay female, captive for
nearly one year, dropped her eggs on 25 July 1975 (David Auth, pers.
comm.). Soil for burrowing was not available in the pen in 1975 and the
eggs were deposited on the enclosure's substrate. The female had
ceased feeding two weeks previous to oviposition and resumed im-
mediately after laying.
Since copulation was not observed in the field, I have no way of
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
knowing with certainty the relation of a female's nest site to the ter-
ritory of the male with which she copulated. However, burrows, or
branches thereof, offering optimum nesting conditions (see later) are
limited in many areas due to substrate conditions and high lizard den-
sities. Therefore, female nest site location is probably not closely deter-
mined by the location of the territory of the male with which she
copulated, but rather by nest site availability. A clustered nest site
distribution in areas with optimal nesting conditions would thus be ex-
pected, and was in fact observed at the SW Blind during the summer
of 1974 (Fig. 22). The nest burrows were clumped in the strip of
relatively deep friable soil lying midway between the rocky ledge adja-
cent to the lake and the rocky seashore. Availability of nest sites is
probably an important factor limiting population size; the success of
egg clutches laid in inferior nests is certainly reduced. The fact that
several other iguanine lizard species migrate considerable distances to
communal nesting areas (Rand 1968; Montgomery et al. 1973;
Wiewandt 1977; Hackforth-Jones MS) suggests that suitable sites
may be generally limiting to members of the subfamily.
Nesting activity is apparently confined to the morning. The
previously mentioned SW Blind site female failed to emerge on 6 June
at her usual time. Under continual observation, the female first
emerged at 1045 hr EST. She climbed immediately into a small Con-
ocarpus tree and began eating leaves.
In the afternoon she returned to the nest burrow to kick additional
soil in to further close the nest chamber. The 5 June Water Cay captive
female had finished nesting by 0900 hr EST 9 June, when she began to
cover the nest. The female captured 4 April nested sometime during
the early part of the day on 12 June.
Cyclura nubila on Little Caymen apparently oviposit late in the
day; Lewis (in Grant 1940b) found nesting females between 1730 and
1800 hrs. Cyclura cornuta (Wiewandt 1977), Iguana iguana (Rand
1968; Alvarez del Toro 1972), and Amblyrhynchus cristatus
(Carpenter 1966) will nest at any time during the day. Sauromalus
obesus is known to nest at midday (Johnson 1965).
Nest burrows are not constructed specifically for that purpose by
female Cyclura carinata as in Cyclura nubila (Street 1952; Shaw 1954),
Cyclura cychlura (Carey 1975), Sauromalus obesus (Johnson 1965),
Iguana iguana (Rand 1968; Hirth 1963a), Amblyrhynchus cristatus
(Carpenter 1966), Cyclura cornuta (Noble 1923; Haast 1969; Wiewandt
1977), Ctenosaura similis (Hackforth-Jones MS), and apparently
Ctenosaura pectinata (Evans 1951). Cyclura cychlura on Andros ap-
parently utilizes termite mounds for nesting in the absence of soil for
digging (Walter Auffenberg, pers. comm.). The terminal portion of a
BULLETIN FLORIDA STATE MUSEUM
FIGURE 22.-Spatial relationship of known nest burrows to deep sandy soils (stippled)
and rocky substrates (hatched) near SW Blind (B). Contour intervals (dashed lines) are
in meters. Scale at left measures five meters. R indicates road.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
retreat burrow is used for the nesting chamber in C. carinata. She may,
however, dig a short branch off the main burrow for the nest chamber.
Figure 23 illustrates a typical nest burrow found on Pine Cay on 9
June 1974. The general configuration of several nest burrows is
diagrammed in Figure 14. As earlier described (see Burrows, under
HABITAT), females tend to inhabit shallower burrows than males.
This is certainly a function of the necessity for relatively shallow bur-
rows by females for use as nest chambers; the roof of no nest chamber
excavated was more than 25 cm below the ground surface.
Following the deposition of the egg complement at the end of the
burrow (or a diverticulum of the same), the female kicks and pushes
sand around the eggs and completely blocks the burrow just proximal
to the eggs, forming a sealed air chamber above the eggs. A similar
chamber is also present in the nests of Amblyrhynchus cristatus
(Carpenter 1966) and Ctenosaura similis (Hackforth-Jones MS). This
chamber apparently aids in the maintenance of high humidity and
perhaps also functions to facilitate respiration of the eggs.
The female obtains the soil necessary for the nest plug from the
area near the mouth of her burrow. The covering process was observed
in part only once in nature. As the female walked through the burrow
toward and out of its entrance, she pushed soil backward with her
forefeet and alternately flung dirt backward with her hind feet. Once
approximately a half meter outside the burrow she would turn and re-
enter the burrow and repeat the sequence. This process was repeated
three times in the instance I observed.
The actual manipulation of the dirt at the nest plug was not ob-
served. It is not known if female Cyclura carinata butt the soil with
their heads while plugging the nest chamber to pack the earth as do
Amblyrhynchus (Carpenter 1966), Iguana (Rand 1968), and Cyclura
cornuta stejnegeri (Wiewandt 1977).
Female C. carinata demonstrated their digging instinct many times
as nesting season approached during early June. Foraging females
would frequently stop and scratch vigorously at the substrate in the
same manner as that observed in the female covering her nest. This
behavior was observed at no other time of the year.
One of the most interesting behaviors associated with nesting
follows the completion of the nesting process itself. Although female
C. carinata are not territorial during the remainder of the year they
vigorously defend the area around their nest (and home) burrow.
A female Cyclura carinata at the SW Blind site defended her nest
burrow against all conspecifics, female and male, at least until 2 July
when daily observation was terminated. Perhaps my presence near her
territory reinforced her defensive instinct and caused an atypical ex-
1979
BULLETIN FLORIDA STATE MUSEUM
FIGURE 23.-Diagram of typical nest burrow of Cyclura carinata excavated June 9,
1974, on Pine Cay, Caicos Islands.
AIR
SIDE -SAND
SIDE
TOP
J
50 cm
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
tension of this behavior. Two other undisturbed females near the SW
Blind were last observed exhibiting this defensive behavior on 10 June
and 12 June, respectively. It is not known when the behavior ter-
minated as they were not seen again. A captive female in Gainesville
exhibited this nest defense for three days following nesting when she
was removed to another pen (David Auth, pers. comm.). Even though
she was moved to a different enclosure she continued to exhibit occa-
sional defensive behaviors for at least 35 days after the transfer.
Subsidence of nest defense behavior seems to be related to
decreases in the number of intruding lizards (i.e. a lack of positive rein-
forcement). At the SW Blind site, as well as in captivity, the behavior
seemed to remain as long as reinforcement from interaction was con-
tinual. The adaptive significance of such a behavioral mechanism
seems apparent. It is clearly advantageous for a female lizard to ex-
pend energy guarding her nest site from other females seeking nest
sites and from males which might inadvertently uncover the eggs dur-
ing burrow cleaning activities. Once the nesting period is completed,
however, and the resident male is aware of the female's burrow, this
energy is better spent on other activities.
The defended area around a female's nest burrow was accurately
mapped in two cases near the SW Blind. During June 1974 female #18
(222 mm SVL) maintained an activity range of only about 155.5 m2,
centered around a low perch overlooking her nest burrow (Fig. 24). I
observed her defend the nest site eight times. Mean radius from the
perch to the site where an intruder was defended was 3.79 0.71 m
(3.0 to 5.2). This radius defines a circular area of 45.1 m2, only 29% of
the female's activity range for the month.
During the same month, another female was observed to guard her
nest eight times. Her defense was centered about a low brush pile
directly above the entrance to her nest burrow. She defended against
intruders which approached within an average of 4.60 1.93 m (1.2 to
7.3). A circular area averaging 66.5 m2 was thus defended. Her activity
range for the month could not be accurately plotted.
Following nesting the female spends most of her time on a perch
near her nest burrow vigilantly watching the area. Three females at
the SW Blind site utilized piles of dead branches within 2 m of the en-
trance to their respective burrows for their elevated guard stations.
For at least the next few days, these females could nearly always be
seen occupying the same perch. A female which nested on 6 June spent
6 hr, 23 min (total active period = 9 hr) at her station on 10 June (with
two defenses of her nest); 7 hr, 1 min on 12 June (with only one nest
defense); 1 hr, 17 min on 16 June (a single defense); 43 min on 21 June
(one defense); 1 hr, 29 min on 26 June (two defenses); and, 51 min on 2
July (one defense).
BULLETIN FLORIDA STATE MUSEUM
On the approach of a conspecific (male or female) the guarding
female would make short lunging charges accompanied by vigorous
open-mouthed bobbing and defensive posturing (see SOCIAL
ORGANIZATION). Biting was never observed in these interactions
and is apparently not part of the female's behavioral repertoire. Most
intruding females and subadult males immediately ran when initially
charged by the guarding female; however, males in whose territory the
nest burrow occurred were more reluctant. In order to discourage the
advance of a resident male, the female usually had to make several
short charges, presenting her postured body laterally to the male bet-
ween lunges, and bobbing vigorously with open mouth. The male
always ultimately moved away, despite the small relative size of the
female; a 222 SVL female (approximate weight, 400 gm) was repeated-
ly successful at driving off the 286 SVL resident male (weight, about 1
kg).
Nest defense was the rule for Cyclura carinata at the SW Blind, but
it is not known if lizards at other locations on Pine Cay or on other
/ ,
FIGURE 24.-Home range, movements and defense of a female Cyclura carinata during
nesting season. Approximate home range is encircled; broken perimeter indicates ques-
tionable limits. Arrow in Blind (B) points due south. Bar scale represents two meters.
Open circle marks nest burrow; solid dots indicate feeding sites. Stars designate sites of
defensive encounters with intruders. Confluence of most movement lines marks the
female's principal perch site when resting.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
islands always exhibit the behavior. Eibl-Eibesfeldt (1966; see also
Carpenter 1966) found that Amblyrhynchus cristatus on islands where
potential nest sites were limited also defended their nests, while those
on islands where nesting areas were plentiful did not. Lizard densities
on Pine Cay were high and available burrows for nest sites were pro-
bably at a premium in many areas. This factor probably limited
population growth to some extent in those areas.
Nest defense, either before or after oviposition, has also been
reported for the iguanines Cyclura cornuta (Wiewandt 1977), Cyclura
cychlura (Carey 1975), Cyclura nubila (Street 1952; Shaw 1954) and
Iguana iguana (Rand 1968) in the field, and Brachylophus fasciatus
(Cogger 1974), C. cornuta (Shaw 1969), and C. nubila (Shaw 1954) in
captivity. In each of these, the aggression level apparently subsides
within a few hours to a few days following oviposition.
The evolution of specialized nest guarding behaviors in at least the
above species of the subfamily Iguaninae suggests that nest sites may
commonly be limiting to all members of the group. Female iguanines
undoubtedly actively seek optimum nest sites, i.e. areas with friable
soil (Carpenter 1967), good insolation (Rand 1972), and/or decreased
predator numbers (Rand and Robinson 1969; Sexton 1975).
Since these areas are often patchily distributed, communal nesting
is common among iguanines: Amblyrhynchus cristatus (Carpenter
1966), Cyclura cornuta (Wiewandt 1977), and Ctenosaura similis
(Hackforth-Jones MS). Sexton (1975) and Hackforth-Jones (MS) have
discussed the advantages and disadvantages of communal versus
dispersed nesting in Iguana iguana, and Ctenosaura similis, respec-
tively; their comments pertain to other iguanines as well.
It should be clear that any behavior that decreases the energy
spent in locating and constructing nest burrows should have a distinct
selective advantage. A variety of strategies have apparently been
employed by iguanines to reduce the cost of nesting. Female Cyclura
carinata avoid excavating a complete nest burrow for each separate
clutch by simply depositing the clutch in previously excavated retreat
burrows (not necessarily one she has previously used as a retreat). A
portion of the energy thus saved is then allocated to short-term nest
defense which decreases the probability of interference with the nest
by conspecifics.
Ctenosaura similis (Hackforth-Jones MS) nests communally; many
females oviposit in the same connecting nest burrow system. Since
many females contribute to constructing the nest burrow, average
energetic cost of nest construction per individual is probably less than
if separate burrows were constructed. Unfortunately, it is not known if
ctenosaurs exhibit nest defense behavior within these burrow systems.
1979
BULLETIN FLORIDA STATE MUSEUM
Iguana iguana (Rand 1968) nests communally; each female oviposits in
a separate nest, which she may or may not have constructed. Since
iguanas are physiologically incapable of completing the nesting pro-
cess in a single bout, they must several times leave the partially con-
structed nest to rest. Since a rested female gains a considerable
energetic advantage if she resumes digging in a burrow already par-
tially completed, females compete for and dispute over these burrows.
Disputes are generally settled via simple (not complex) displays rather
than by actual fighting. Rand and Rand (1976) have argued
stochastically that these competitive disputes are actually settled
with a minimization of energetic cost to the individual. Their cost
argument probably relates as well to the similar behavior of Cyclura
cornuta (Wiewandt 1977) and Amblyrhynchus cristatus (Carpenter
1966).
EGGS, INCUBATION, AND HATCHING
No information is available in the literature concerning reproduc-
tive potential in Cyclura carinata. Only a single clutch of eggs is laid
annually. Based on number of oviducal eggs and/or corpora lutea,
clutch size in C. carinata averages 4.38 1.95 (2-9; N = 18), and is
positively correlated with SVL length (Fig. 25). An increase of one egg
for about 16 mm SVL is indicated by the least square regression
estimate (clutch size = 0.064 SVL 10.018; r = 0.741, p < 0.01).
Estimation of clutch size by counting enlarged ovarian follicles
from lizards collected during the spring tends to slightly overestimate
the actual number of oviposited eggs (X = 4.80 0.98; N = 5).
Numerous excavated burrows contained hatched egg shells
somewhere along their lengths, but their numbers were deemed
unreliable as an estimate of clutch size and therefore were not included
in any of the above calculations. The numbers of shells found in these
cases were 1,1,3,5, and 7. It is doubtful that Cyclura carinata ever lays
a single egg only and these shell records probably reflect my inability
to find the entire clutch. The grand mean for clutch size from females
with enlarged follicles, oviducal eggs, or corpora lutea; natural
nestings observed; captive layings; and excavated nests is 4.65 1.77
(2-9; N = 26).
Clutch information from two additional females was not included in
the above calculations because of their captive maintenance, and the
possible implications of their captive reproductive life. A 285 mm
SVL, 770 gm lizard (the heaviest female encountered in the study) was
captured 28 July 1974, by David Auth on Water Cay. Maintained in
captivity on a generous diet, she laid seven eggs on the enclosure floor
on 25 July 1975. She appeared very healthy until her sudden acciden-
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
tal death on 24 May 1976. Dissection revealed 11 yolked follicles of
near-ovulatory size in the ovaries. A potential clutch size of 11 is in-
dicated. Another Water Cay female, captured 16 February 1976, (292
mm SVL) laid 11 eggs in captivity 25 July 1976. Clutch sizes in these
two females thus exceed by two the nearest record. This apparent
jump in reproductive output could be related to the increase in quanti-
ty and quality of food resources available to them in captivity. The im-
plications of these observations will be discussed later.
Twenty eggs (oviducal or freshly laid) averaged 51.8 mm (46.0-58)
by 31.1 mm (28.5-33.5) and weighed an average of 25.9 (19.0-29.9) gm.
Eggs are elongate ovals when laid; the elastic shell is thin and translu-
cent and an embryonic disk 1.5 to 2.0 cm in diameter is faintly visible
through the integument. The shell soon thickens, loses its translucent
character, and becomes an immaculate white.
3-1 *
3
0 *
200
FIGURE 25.-Relationship of clutch size to snout-vent length (in mm) in Cyclura
carinata. Number of eggs based on counts of oviducal eggs and/or corpora lutea only.
1979
BULLETIN FLORIDA STATE MUSEUM
Two clutches of 6 eggs each were incubated to hatching in the man-
ner of Zweifel (1961); only 3 of 6 hatched successfully in both cases. To
minimize disturbance the widths of only 3 eggs were measured during
incubation. Average width had increased to 38.3 mm at 18 days
prehatching. This increase in diameter continued to a maximum at
hatching; egg length increased very little during incubation. One egg,
which increased exceptionally in size, weighed 46.0 grams just prior to
hatching. Such an increase in egg size and weight is typical of iguanid
lizard eggs (e.g. Crenshaw 1955).
One of the incubated clutches (Clutch A) was excavated from a nest
burrow on Pine Cay 9 June (see Table 7) and was surely less than one
week post-oviposition. Incubated at room temperature on Pine Cay un-
til 20 July, the eggs were then transferred to a constant 280C environ-
ment in the laboratory in Gainesville. Prior to 20 July, two eggs had
developed fungus, collapsed, and were removed. The first had shrivel-
ed on 15 June (6 days after discovery) and contained an embryo of 34
mm total length. The second collapsed on 4 July (25 days post-
location); the contained embryo measured 45 mm total length.
At 1800 hr, 2 September (85 days since discovery), hatching began.
Two to four longitudinal slits were made in each egg shell by the
lizard's egg tooth. Three young had completely emerged by noon on 4
September. On dissection the fourth egg was found to contain a fully
developed, stillborn fetus which had apparently been unable to escape
the egg. The first hatchling was completely out of his egg within 18
hours of slitting the egg; the second required 10 hours; the third, 19
hours.
The other incubated clutch (Clutch B) was laid in captivity on 12
June 1975, by a female captured 4 April 1975 on Pine Cay, and main-
tained in an outdoor observation enclosure in Gainesville. She was
first copulated with on 26 April, and at least one more time on 27 April
by a different male. Following deposition, the six eggs were removed
immediately to an environmental chamber and incubated in sterile
sand at 30C. Three eggs spoiled during incubation and were discard-
ed. During the afternoon of 22 September (101 days postoviposition),
hatching began. By 1815 hr that evening, the heads of two hatchlings
protruded from their respective eggs through a single longitudinal slit
16-19 mm long located dorsally on the eggs approximately 1/3 the
distance from their ends (Fig. 26). Because of the continual distur-
bance while photographing the hatching process, the young required
approximately 44 and 65 hours respectively to gain complete freedom
from their eggs. The third egg had not been pipped by 0800 hr, 24
September, and was opened. The contained fetus was fully formed and
alive, but had badly deformed hind limbs. In addition all three of the
young had the distal portions of their tails twisted and shortened.
Vol. 24, No. 3
T\wI.: 7.-S i..Sicl:('Ir ) Ri-:' Roi)O(]TivI: DxVi\ 'it-(M Fh:i \li.: Cvclura carinata.
Pre-
Date SVL oviposition
Location Nesting (mm) Weight (gm)
Pine Cay June 3 (0)
Water Cay
Pine Cay
Pine Cay
Pine Cay
June 5 (N)
June 7 (N)
June.9 (N)
June 9 (N)
Pine Cay June 9 (0)
Water Cay June 9
(C; June 5)
Pine Cay June 12
(C; April 4)
Pine Cay June 18, died
with oviducal
eggs
(C: April 3)
Pine Cay Between June
13 July 15
(C; April 5)
Accumulated Averages
Clutch
Weight
(gm)
245 520 142
Post-
oviposition Clutch Mean Egg Mean Egg
Weight (gm) Size Size (mm) Weight
(gm)
5 56.0 x 32.2 28.3
(54.5-58.0 x 31.0-33.5)(27.2-29.9)
255 -207.2* 645 8
200 -51.8* 250 2
200 -77.7* 285 3
- 155.4* 6 52.4
(51.5-54.0)
235 510 126.2 380 6 49.1 x 29.5 21.0
(46.0-52.0 x 28.5-30.25)(19.0-23.1)
250 815 250 568 9 49.5 x 31.5 27.8
(49-50 x 31-32)
235 570 155.4* 6 51.0 x 32.2
(50.5-51.5 x 30.0-33.5)
235
560 77.7*
216 440 129.5*
230 569.2 137.3
(excluding
estimates
= 172.7)
425.6 5.3 51.8 x 31.1
RE EPP x 10'
0.273 5.46
0.243* 3.04
0.172* 8.60* O
0.214* 7.13*
-
0.247 4.12
0.307 3.41
Z
0.273 4.55
0.139* 4.63*
0.294* 5.88* O
0
0
2z.9 U.Z4U 5.ZU
(excluding (excluding
estimates estimates
= 0.275) = 4.33)
No I : (N) by date indicates date nest found: IO) indicates female with oviducal eggs. and ICI captive nesting Iwith date female collected). Observed range included in parentheses below
means. Asterisks signify values estimated from overall average egg weight. Reproductive effort (IE) measures proportion of clutch weight in preoviposition weight of female.
Expenditure per progeny (EPPI is the proportion of female weight made up by a single egg.
oc n
BULLETIN FLORIDA STATE MUSEUM
FI(;uRE 26.-Hatching in Cyclura carinata. See text for explanation. (A) 1815 hrs 22
September 1975; (B) 0815 hrs 23 September 1975.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
Parker and Pianka (1976) found similar tail deformities among both
captive hatchlings and wild Crotaphytus wislizeni in Utah. Bustard
(1969) has suggested that such tail abnormalities may result from high
temperature incubation of eggs. Field temperatures measured at
depths representative of nest locations indicated a nearly constant
28-290C through June and July. Incubation of the captive clutch at
higher than natural temperatures (300C) may have produced the
observed deformities.
Incubation temperatures in natural nests have been recorded for
several other iguanine lizard species. Bartholomew (1966) found
temperatures in Amblyrhynchus varied between 280C and 300C. Ig-
uana iguana nest temperatures in Panama (Rand 1972) were quite con-
stant and ranged only between 310C and 320C; however, temperatures
recorded in Costa Rica by Hirth (1963a, 1963b) and Mueller (1972) in
Colombia at typical nest depths on nesting areas fluctuated from
27.8 C to 31.4 C, and 29.7 C to 30.3 C, respectively. Temperatures in
nest burrows of Ctenosaura similis in Costa Rica ranged between
30.0C and 31.50C (Hackforth-Jones MS). Johnson (1965) found
temperatures in a single nest of Sauromalus obesus varies from 32.20C
to 36.1C. It is apparent that only minor temperature fluctuations
characterize the nests of iguanine lizards.
No direct field data are available for the incubation period in
Cyclura carinata but evidence indicates a term of about 90 days. A
metal enclosure was placed around a recently laid nest burrow ex-
cavated on Water Cay on 5 June 1974. The nest had hatched and the
young were above ground within the enclosure when checked on 30
August (86 days after discovery). Yolk remnants in their guts in-
dicated they were very recently hatched. Hatchlings were seen emerg-
ing and dispersing from two previously unlocated nests at the SW
Blind on Pine Cay on 1 September 1974.
Young of the year have been captured on Pine Cay on 31 August
1974 (2), 5 September 1974, 8 September 1974, and 18-20 September
1973 (10), and were very common during early and mid-September.
The earliest collection date for a new hatchling was 10 August 1975, on
Little Water Cay. On that date, 22 additional juveniles were captured
and released, and all were at least one year old. An obviously recently
hatched C. carinata with exposed umbilicus and remnants of yolk in its
gut, was collected on Fort George Cay on 23 September 1973.
Since eggs are laid during the first two weeks of June and hatch
during late August and early September, an incubation period of three
months (approximately 90 days) is indicated. The captive hatching of
Clutch A, estimated to be a week old when found, after 85 days, fur-
ther supports this figure.
BULLETIN FLORIDA STATE MUSEUM
Hatchlings measured in early September ranged from 76 to 83 mm
SVL (X = 79.80; N = 20) and 108 to 121 mm TL (X = 113.6; N = 17).
Captive hatchlings were smaller than those naturally hatched; three
from Clutch A averaged 74.1 mm SVL (73.0-76.2 mm) and two from
Clutch B, 72.75 mm (72.0-73.5). Tail lengths from the Clutch A hatch-
lings ranged from 104.8 mm to 106.4 mm (X = 105.9).
Nine recently hatched lizards on Pine Cay weighed in early
September averaged 14.62 gm (12.5-15.0). Three captive hatchlings
averaged 15.69 gm (13.4-17.3) immediately after leaving their eggs.
The higher weight is due to the bulk of the freshly absorbed yolk sac.
The same three lizards weighed 10 days later averaged 14.34 gm
(12.2-15.6).
Hatchling rock iguanas are basically identical to the adult female,
except for the longer tail and the proportionately larger head (see
GROWTH), the more brilliant laterally striped pattern and the
presence of the egg tooth.
FERTILITY, PRENATAL AND NATAL MORTALITY
No oviducal eggs or freshly laid eggs (representing five clutches,
totaling 32 eggs) examined lacked embryonic disk development.
Although the sample size is quite small, a fertility rate close to 100 per-
cent is indicated.
Estimates of natural prenatal mortality come from only four nest
chambers excavated following the hatching period. Since spoiled eggs
are easy to distinguish from the crisp parchment-like empty shells of
successfully hatched eggs, mortality rates for these clutches during in-
cubation were determined. Unsuccessful eggs and their respective
total complement size included 3 of 3, 1 of 5, 1 of 8, and 0 of 7. Mortali-
ty rates therefore averaged 33.1 percent among these clutches (range 0
to 100%). However, this estimate is not weighted with respect to
clutch size and tends to overestimate mortality. If we total the number
of bad eggs and compare this to the total of all four complements, the
mortality rate is 21.7 percent and may be a more reliable estimate
despite the small sample size. Wiewandt (1977) found a 14 percent
mortality rate in natural nests with single clutches for Mona Island
Cyclura cornuta.
One of the most critical stages in the life history of Cyclura carinata
occurs shortly after hatching, between the time the bulky yolk sac is
drawn into the body cavity and the time the mid-ventral cleft through
which the sac was drawn is securely closed. In that interval the lizard
must necessarily rest since disturbances provoking movement by the
hatchling, whether they be from siblings in nature or observers in the
laboratory, will cause the closing umbilicus to rupture. The resulting
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
hemorrhage and the subsequent inability of the lizard to successfully
retract the yolk sac into his body cavity lead to the eventual death of
the individual. Synchronization of hatching processes in a nest
chamber providing little sensory input is therefore of utmost impor-
tance to successful hatching in Cyclura carinata.
Once the hatching process is complete, the lizards must still escape
their incubation chamber. Their success at this time is reflected in the
fact that of six nest burrows excavated after hatching, none contained
a dead hatchling lizard. Freedom is gained via a narrow escape tunnel
(or tunnels) dug by the hatchlings vertically from the nest chamber.
The proximity of the nest chamber to the substrate surface simplifies
the process (see Nesting). However, escape from the nest chambers
constructed under flat limestone or compacted coral sand rocks is
necessarily different. Only one such hatched nest was excavated. Con-
siderable scratching at all walls of the chamber was evident and the ex-
cape tunnel had ultimately penetrated the nest plug and the lizards
had apparently emerged through the main burrow. This alternative is
always available should vertical escape be impossible.
The importance of sibling facilitation (as noted in sea turtles; Carr
and Hirth 1961) in Cyclura carinata digging out of the nest is
unknown, but it is logical to assume that the presence of more digging
hands would increase the probability of a more rapid, successful
emergence. Experimentation with monitored nests would be very in-
teresting.
GENERAL SEASONAL REPRODUCTIVE PATTERN
The timing of the major events of the reproductive cycle of Cyclura
carinata is illustrated in Figure 27. A general model relating en-
vironmental, physiological, and behavioral changes during the
reproductive cycles of male and female Cyclura carinata is shown in
Figure 28. Although partly hypothetical, this model describes well the
YOLKED FOLLICLES
MATING
SOVIDUCAL EGGS
S NESTING
CORPORA LUTEA
HATCHING
J F M A M J J A S O N
FIURE 27.-Annual reproductive pattern of Cyclura carinata.
BULLETIN FLORIDA STATE MUSEUM
Vol. 24, No. 3
synchronization of biotic and abiotic events in the annual cycle of the
rock iguana.
Three basic patterns in the timing of tropical iguanine reproductive
cycles are evident. In the first, nesting coincides with the beginning of
the rainy season, with hatching occurring well into that season. This is
the pattern followed by Cyclura cornuta (Wiewandt 1977), Cyclura
cychlura (Carey 1975), C. pinguis (Carey 1975), and Cyclura carinata
(this study). For these species, the reproductive cycle appears to be
seasonally timed to reduce the possibility of egg desiccation and to in-
sure an abundant food supply, especially fruits, for hatchlings. The se-
FEMALE COMPONENTS:
DATE Behavioral Phy
ENVIRONMENTAL VARIABLES
MALE COMPONENTS
slologicaI Physiological Behavioral
Jan Increasing Radiation and temper-
ature (with decrease in precipi-
ration)
General t Testicular
Activity enlargement General increase
increase in activity
(maintenance of
normal terri story
Feb. Follicular
vitellogenesis
Mar.
April Testicular Increased interest
Max mum nfeneles
Rejection of Initation of
courting males Courtship behavior
Ovulation and Testicular
May Mating-l----- c concmitant (7) regression Mating
receptivity
Shelling of Nortal activity
oviducal eggs resumes
June Choosin of -Beginning of Rainy Season
Nest site
Nesting and
associated
guarding
Decrease in Luteal
nest guarding regression Increasing precipitation
July NormI activity Increasn in plant
resumes reproduction (and
associated structures)
Aug. Decr asking
radiation and
tempera tures
H_____ ATCH ING HATCHING
Sept,.
Oct. Decrease in plant
reproduction
Nov.
Decrease in Decrease in
general activity general active ity.
Dec.
Fi;uiR: 28.-A hypothetical model relating environmental, physiological, and
behavioral changes to the reproductive cycles of male and female Cyclura carinata.
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
cond strategy involves nesting during the dry season, with hatching
coincident with the beginning of the rainy season. Iguana iguana and
Ctenosaura similis adhere to this schedule (Davis and Smith 1953;
Hirth 1963a; Rand 1968; Alvarez del Toro 1972; Fitch 1973b). Both
Rand (1972) and Fitch (1973b) agree that this cycle is dictated by the
lack of optimal incubation temperatures during any other time of the
year. In addition, the cycle is advantageous to hatchlings that are
folivorous or insectivorous since these resources are available soon
after the beginning of the rainy season.
In the last pattern, nesting occurs toward the end of the rainy
season, and hatching early in the dry season. Amblyrhynchus
cristatus is the only species known to conform to this schedule
(Carpenter 1966). Unfortunately, since this species is a littoral feeder
(mainly marine algae), and food resource productivity and availability
have not been studied, the significance of the timing of its reproduc-
tion cycle is unknown.
There is some disagreement concerning the timing of the reproduc-
tive cycle in the genus Conolophus; nesting in November to January
(the rainy season) is suggested by Van Denburgh and Slevin's (1913)
and Slevin's (1935) data; however, DeVries (1974) reported nesting in
May and June (during the dry season). This apparent paradox deserves
further study.
REPRODUCTIVE EFFORT AND STRATEGY
Recent studies argue that the ratio of clutch weight to preoviposi-
tion body weight may not accurately reflect the proportion of energy
allocated to reproduction, especially in lizards producing multiple
seasonal clutches (Tinkle and Hadley 1973, 1975; Vitt 1974; Vitt and
Ohmart 1975; Tinkle 1976). The clutch weight-body weight ratio (ab-
breviated RE, for reproductive effort) tends to underestimate a
similarly derived ratio of actual calories (Tinkle and Hadley 1975; Vitt
and Ohmart 1975). Unfortunately, the lizard literature contains con-
siderably fewer of the latter estimates than the former. Nevertheless,
the clutch-to-body-weight ratio is still of value in making general in-
terspecific comparisons of reproductive effort.
A similar argument can be raised for estimates of expenditure per
progeny (EPP) based on the proportion of preoviposition female
weight in a single egg. However, for broad comparisons, this measure
is probably adequate.
Selected reproductive data, including RE and EPP, for individual
female Cyclura carinata appear in Table 7. RE in Cyclura carinata
averaged slightly less than one-fourth and ranged from 0.139 to 0.307
for nine females. This value falls well within the range of similarly ob-
245
BULLETIN FLORIDA STATE MUSEUM
trained values in the lizard literature as compiled by Pianka and Parker
(1975: Range 0.05 to 0.30 X = 0.173; N = 70+ species), Tinkle (1969:
0.10 to 0.40; N = 14) and myself (0.10 to 0.40; N = 27). However, the
value obtained for C. carinata is greater than the average for those
species. Unfortunately, speculation on specified reproductive
strategies based on these data is complicated by the fact that the ma-
jority of the lizard species for which data on reproductive effort are
available produce multiple clutches, while the values reflect only single
clutches. Since all the iguanine lizards apparently oviposit only once
per year, comparisons within the group should be more meaningful.
EPP values for C. carinata ranged from 3.04 to 7.13% and averaged
5.20%. This is a relatively high value among lizard species. Estimates
of EPP for several species calculated from the literature averaged from
about 2 to 7% (Telford 1969; Avery 1975a; Parker and Pianka 1975,
1976; Pianka and Parker 1975; Vinegar 1975; Vitt and Ohmart 1975).
However, one value calculated from a single female Tachydromus
tachydromoides (11.2%) exceeded this range (Telford 1969). This value
is probably approaching the limit that is possible for lizards.
Among nine clutches, there is a significant negative correlation of
EPP with female SVL length (r = -0.92, p < 0.01) and clutch size (r =
-0.85, p < 0.01). Older females lay more eggs, but expend less energy
per egg. As expected, RE is positively correlated with clutch size (r =
0.74, 0.05 > p > 0.01. It is, however, not significantly correlated with
female SVL (r = 0.40, p > 0.05). In comparison to other lizard species,
Cyclura carinata demonstrates a high reproductive expenditure per
clutch as well as per progeny; relatively few large eggs are produced
annually.
The iguanine lizards have been poorly represented in previous
analyses of reproductive strategies, due to a dearth in basic reproduc-
tive data for the included species. No species has been fully studied
reproductively; basic reproductive parameters remain unmeasured
(especially weights) even for otherwise well-studied iguanines like Dip-
sosaurus and Sauromalus. I have scoured the literature as well as the
knowledge of my colleagues in an attempt to compile and analyze
reproductive data for lizards of the subfamily Iguaninae. This informa-
tion, supplemented by some of my own unpublished data, appears in
Table 6.
This table illustrates the general deficiency of our knowledge of ig-
uanine reproduction. Several comparisons can, however, still be
drawn. Cyclura carinata lays the fewest eggs (X < 5) of any studied ig-
uanine except Amblyrhynchus (2-3) and perhaps C. cychlura (3-7).
Ctenosaura similis can lay nearly 20 times as many eggs as Cyclura
carinata. Only Amblyrhynchus, Conolophus, Cyclura nubila, and C.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
cornuta are known to lay larger eggs than Cyclura carinata. However,
the eggs of Ctenosaura similis are only half the length and one-fifth
the weight of those of C. carinata. Each of these comparisons suggests
considerable variation in reproductive expenditure among this other-
wise homogeneous group of lizards. Within the subfamily reproductive
strategies fall into two basic categories (after Iverson MS): the produc-
tion of large clutches of relatively small eggs (as in Iguana iguana and
Ctenosaura similis) and the deposition of small clutches of relatively
large eggs (most of the remaining species, including Cyclura carinata).
I am currently studying the selective advantages of these strategies to
the species exhibiting each.
GROWTH
GENERAL PATTERN
Cyclura carinata ranges from about 80 mm SVL and 15 grams at
hatching to over 290 mm SVL and 1100 grams in females and nearly
360 mm SVL and 1900 grams in males (Fig. 29). The relationship be-
tween the logarithm of snout-vent length and that of body weight is
significantly linear:
Log Wt = 3.0336 Log SVL 4.496
(r = 0.987, d.f 176, P < 0.0001).
This equation is equivalent to Wt = (3.202 X 10-s) SVL3-336, where Wt
= weight in grams, and SVL = snout-vent length in mm. Curves for
females (plus juveniles) and males (also with juveniles) are not
significantly different from the overall curve.
An ontogenetic reduction in head size relative to body size occurs in
Cyclura carinata from hatching to maturity in males and throughout
life in females (Fig. 30). Older males, however, do exhibit a secondary
increase in proportional head size. Hypertrophy of the head
musculature contributes significantly to the visual image of a massive
head in aging males. This cephalic enlargement in Cyclura carinata
does not however reach the magnitude that it does in old male Cyclura
cornuta, but as in that species (Wiewandt 1977), it may be important
in social contexts, especially male-male interactions (see SOCIAL
ORGANIZATION).
At hatching relative tail size is maximal, decreasing in length pro-
portional to body length throughout life (Fig. 31). There is no sexual
difference in relative tail length; however, the girth at the tail base is
proportionately larger in males due to the presence of the hemipenes
internally.
Variation in maximum size (and weight) between populations of
Cyclura on the study islands is notable (Tables 8 and 9). Adult Cyclura
248 BULLETIN FLORIDA STATE MUSEUM Vol. 24, No. 3
carinata from Water and Little Water cays are larger (and more
yellow; see Color under MORPHOLOGY) than those from Pine and
Fort George cays. Since the islands are so similar phenetically, this
divergence may be related to genetic differences in the colonizers of the
two groups of islands.
The sexes of Cyclura carinata are strongly size dimorphic; female
SVL and weight average 81.5 and 50.9% that of males, respectively
*
18-
17-
16- 0
0
15-
14-
13-
12 -
0 10-
xd 0
6 8- **
i*
7- O O
6- 0O
3- O O *
081
2- .roe
0
80 120 160 200 240 280 320 360
BODY LENGTH (mm)
FIGURE 29.-Relationship of body length (SVL) to weight. Solid circles above 180 mm
SVL indicate males; open circles, females. Each symbol represents at least one in-
dividual. Data from 181 lizards.
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
(Tables 8 and 9). Amblyrhynchus, Ctenosaura similis, and Iguana ig-
uana all exhibit this great size dimorphism. Female Amblyrhynchus
average 85.0% of male SVL and 50.0% of male body weight (Carpenter
1966); female Ctenosaura similis measure 80.0% and 55.6%, respec-
tively (Fitch and Henderson 1977a); and Iguana iguana average 73.6%
(Fitch 1973a) to 90.6% male SVL (Fitch and Henderson 1977b). Males
are also larger than females in all the other iguanine species for which
data are available (see Table 6); however the dimorphism is extremely
reduced. Female Cyclura cornuta, Cyclura pinguis, Conolophus sub-
cristatus, Ctenosaura pectinata, Dipsosaurus dorsalis, Enyaliosaurus
clarki, and Sauromalus obesus all average only slightly smaller than
males of the same species (references in Table 6).
HEAD WIDTH
(mm)
.5
0
O
O
0
000
00 0
O
008
go
*
**
* 0
FIGURE 30.-Relationship of headwidth across tympanum to body length (measured
snout to vent). Solid circles above 170 mm body length indicate males; open circles,
females. Each symbol represents at least one individual. Data for 77 lizards.
1979
BULLETIN FLORIDA STATE MUSEUM
The sexual size dimorphism observed for C. carinata may be the
result of intense sexual selection as a consequence of its generally
polygynous mating system and/or as a mechanism to reduce in-
traspecific competition for food (see later).
Comparisons of lizard size-frequency plots by month of capture
suggest several discrete juvenile age classes. Although the use of these
32-
E
I -
I -
0
Z 24-
LU
_J
16-
8-
*
ooo
o %
000
09 O
J: 0
a
*.-:
I I I I I l lI1 I I l
80 120 160 200 240 280 320 360
BODY LENGTH (mm)
FIGURE 31.-Relationship of body length (measured snout to vent) to tail length. Solid
circles above 170 mm body length indicate males; open circles, females. Each symbol
represents at least one individual. Data from 179 full-tailed lizards.
Vol. 24, No. 3
TABLE 8.-COMPARISON OF SNOUT-VENT LENGTH IN Cyclura carinata ON FOUR OF THE STUDY ISLANDS.
Fort George Pine Cay Water Cay Little Water Cay Total
X=221.75 30.46 X=218.24 17.19 X=256.6 22.79 X=231.11 15.01 X=225.39 22.56
9 191 -267 190 260 222 292 191 -254 190 292
N=4 N=27 N=5 N=9 N=45
X=237.17 28.64 X=270.12 32.29 X=314.69 44.84 X=261.64 43.61 X=276.26 46.37
0' 203 286 216 318 191 30 191 318 191 -360
N=6 N=17 N=13 N=11 N=47
NOIE: Data from lizards over 190 mm SVL only. Means + one standard deviation appear with range and sample size.
TABLE 9.-COMPARISON OF BODY WEIGHT IN Cyclura carinata ON FOUR OF THE STUDY ISLANDS.
Fort George Pine Cay Water Cay Little
X=366.25 160.68 X=433.46 97.63 X=749.83 187.80 X=42
9 205-610 250-570 535 1135 3
N=4 N=13 N=6
X=470.00 165.58 X=832.5 231.65 X=1451.67 344.00 X=64
O" 265-735 460-1110 750-1864 25
N=6 N=8 N=12
NOTE: Data from lizards over 190 mm SVL only. Means + one standard deviation appear with range and sample size.
SWater Cay
8.89 71.17
15 540
N=9
6.3 319.84
6 1215
N=10
Total
X=475.59 193.40
205-1135
N=32
X=935.08 479.98
256 1864
N=36
BULLETIN FLORIDA STATE MUSEUM
size distributions to estimate growth rates can be misleading (Tinkle
1967b), when used in conjunction with mark and recapture data
reliable growth information can be obtained. Actual growth data on
Cyclura carinata are difficult to acquire even on islands uninhabited by
man and his animals. Collection of such data on disturbed islands is
nearly impossible. Slow adult growth and the difficulty in accurately
measuring a struggling lizard with a total length of over half a meter
and weighing over half a kilogram compound the difficulty in obtain-
ing accurate natural growth information. On Pine Cay predation on
juvenile lizards by feral mammals made abortion of a mark-release-
recapture program there necessary early in this study; during four
visits over one year 30 juveniles were marked and none recaptured. A
similar recapture program initiated on uninhabited Little Water Cay
(Fig. 5) proved satisfactory. A total of 103 lizards was marked on five
visits (10 July and 4 December 1974, 10 August 1975, 5 May and 10
June 1976), and 19 were subsequently recaptured at least once.
Growth in juvenile Cyclura carinata based on actual recapture data
as well as analysis of size-class information is plotted in Figure 32.
Based on size at sexual maturity, males require 7 to 8 yr to reach
maturity (about 220 mm SVL); females, 6 to 7 yr (185-200 mm SVL).
Size-class data indicate an average hatching SVL of 80 mm (weight =
19.0 gm from regression equation); juveniles average 100 mm (37.4
gm) at 1 yr, 124 mm (71.8 gm) at 2 yr, 146 mm (117.8 gm) at 3 yr, 161
mm (158.5 gm) at 4 yr, 178 mm (214.9 gm) at 5 yr, and 195 mm (283.5
gm) at 6 yr. Only a slight decrease in growth rate (measured as change
in SVL length) occurs from hatching to maturity. An average growth
rate of approximately 19.2 mm SVL (range = 15-24) per year, or 1.6
mm per month, is indicated. Similar results are obtained from in-
dividual growth records of recaptured Little Water Cay lizards as well
as of several captive Pine Cay juveniles (Fig. 33, Table 10). A single
captive juvenile lizard maintained in captivity for 16 months increased
in body length from 129 to 178 mm SVL, a growth rate of 5.5
mm/month. This atypically high value was not used in any of the
calculations, since it presumably represents growth under optimum
conditions. The slopes of each of the regression equations in Table 13
evidence the nearly constant juvenile growth rate.
Mean change in tail length per month for recaptured Little Water
Cay lizards less than 180 mm SVL with complete tails was 2.365
1.30 mm (N = 13). The data suggest relatively constant rates of tail
growth in juvenile Cyclura.
Despite their tropical location, there is considerable seasonality in
both temperature and moisture in the Caicos Islands. This is reflected
in the phenology of the vegetation and ultimately in the growth and ac-
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
11'
is
17.
16.
15-
11-
10-
9-
20
19
18
17
16
15
14
S13-
12
11-
10
9-
8
7.
1*1 I I I
26 6
253
H 1 2 3 4 5 6 7
AGE (YRS)
FIGURE 32.-Growth in juvenile Cyclura carinata based on actual recapture data (top)
and size class distribution (bottom). Snout-vent lengths in centimeters. Means (horizon-
tal lines connected by curve), range (vertical line), standard deviation (heavy solid ver-
tical line) and sample size for each size range class sample are indicated. Horizontal bars
below curve in lower graph mark annual period of slow growth (December to March).
Total sample size = 206.
Z
BULLETIN FLORIDA STATE MUSEUM
tivity of Cyclura in the islands. During the cold, dry season of late
December through March, there is very little plant growth. Growth in
juvenile lizards (and presumably adults) also slows considerably. This
growth reduction in Cyclura is apparent in Figure 32 (bottom) if the
slope of the curve during the harsh winter season (marked by horizon-
tal bars below the growth curve) is compared to that for the remainder
of the year. The slope of the curve (equivalent to growth rate) during
the winter season (X = 0.992 mm/month; range 0.30-1.39) is
significantly different (p < 0.05) from the slope for the remainder of
the year (X = 1.855; range 1.15-2.30). This winter decrease in growth
rate is related not only to a decrease in food quality and quantity (pers.
observe ; Auffenberg MS) but also to a reduction in activity
necessitated by the cooler temperatures (see ACTIVITY AND
MOVEMENTS).
Mean body size (SVL) and weight for yearly intervals (see above)
were utilized to construct a curve relating change in body weight to
body size for juvenile C. carinata. Actual weight changes in recaptured
lizards for the most part fit that curve very well (Fig. 34). Both sets of
data indicate a nearly constant annual increase in body weight change
3 -
*
o
2 0 0 0
0
Se 0
at 0
o
0 0
0
S- *o
1 10 12 14 16 18 20 22 24
BODY LENGTH (cm)
FIGURE 33.-Growth rate (mm SVL per month) of recaptured lizards on Little Water
Cay (closed circles) and captive lizards from Pine Cay (open circles) plotted by the
average of the body lengths at first capture and at recapture.
~
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
TABLE 10.-REGRESSIONS OF BODY SIZE ON GROWTH RATE FOR FOUR CATEGORIES OF DATA
FROM FIGURE 33.
Little Water Cay recapture data
(lizards < 200 mm SVL only)
All Little Water Cay data
Little Water Cay and captive data
(< 200 mm SVL only)
All Little Water Cay and captive
data
Regression
Equation (X =
mm SVL; y =
growth rate [mm
X SVL/month]; and Critical
Growth rate r = correlation value for
(mm SVL/month) coefficient) r
1.74 0.63 y=0.0033X + 1.34 0.468
N=18 r=0.138 (5%)
1.58 0.77 y=-0.0081X + 2.65 -0.444
N=20 r=-0.439 (5%)
1.85 0.80 y=-0.00083X + 1.98 -0.388
N=26 r= -0.061 (5%)
173 0.90 y=-0.0094X + 2.92 -0.496
N=28 r=-0.718 (1%)
(X = 10.03 gm/year) through at least the first 6 yr of life.
Very little information on growth rates of adult Cyclura carinata
was obtained during the course of the study. Only one adult lizard of
those few marked on Little Water Cay was recaptured. Although
many lizards at the SW Blind site were remeasured, the value of the
data is questionable due to the difficulty in accurately measuring the
large lizards; negative growth rates (SVL change/month) were occa-
sionally recorded. Nevertheless, an extremely slow adult growth rate
is suggested. The mean change in SVL per month for males at the SW
Blind was 0.18 mm (N = 12). However, all but three (4 recapture
records) of these lizards were obviously old, territorial-holding males. I
therefore believe that this extremely low estimate of mean growth rate
reflects the very slow growth of older males. The mean growth rate
(mm SVL/month) in the smaller males (250-270 mm SVL) is 0.659 (N =
4) and is probably a more accurate estimate of growth in adult male
lizards.
A mean growth rate for females slightly more than half that of
males (0.461 mm SVL/month; N = 4) is indicated by the SW Blind and
Little Water Cay recapture data. This is as anticipated since the dif-
ference between SVL at maturity and maximum size in females is only
half that for males.
In a further attempt to determine the rate of growth in adult ig-
uanas, the relationships of body size to the mid-dorsal spines were in-
vestigated. As explained under MORPHOLOGY, once maturity is
reached in males the spines on the neck begin elongation (Fig. 7).
I
BULLETIN FLORIDA STATE MUSEUM
Thereafter each time the skin is shed an annulus is formed around the
base of the spine. The back spines begin a similar development (in-
cluding rate) after the skin is twice cast (Fig. 35). Therefore, neck
spines possess two more annuli than back spines. Tail spines also
8-
7 9 11
13 15 17 19 21
SVL [cm]
FIGURE 34.-Relationship of weight change (gm/month) to body size in juvenile Cyclura
carinata. Hollow circles are actual weight change records from recaptured Little Water
Cay lizards, plotted by the average of the original and the recapture snout-vent lengths.
Solid circles represent calculated weight changes: mean snout-vent lengths for one year
age intervals were used to calculate body weights with the regression equation:
Wt = (3.202 x 10-s)SVL3 .. ; consecutive yearly weight changes were divided by 12 to
give monthly values. These are plotted by the average of the mean snout-vent lengths
at the beginning and end of the sample year.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
elongate in older males, but annuli are not formed. The dorsal spines of
females develop little and generally do not bear annuli (Fig. 36). With
age the dorsal spines are worn smooth and the number of annuli are un-
countable. However, it is frequently possible to determine with some
accuracy the number of annuli present. Unfortunately, the spine
sheaths are not shed precisely at the time the adjacent skin is
sloughed, and annuli counts therefore tend to be underestimated.
Since the spines indicate previous ecdyses, it should be possible to
estimate age in male lizards by the number of annuli on their spines.
But some knowledge of the time between molts is necessary. Accurate
data on shedding frequency are difficult to obtain; Tinkle (1967b:43)
has discussed the problems inherent in their estimation. From adult
lizards painted both on Little Water Cay and at the SW Blind an an-
nual slough is indicated. Furthermore, adult Cyclura carinata from
Water Cay maintained in captivity by David Auth during the course
of thermoregulatory studies shed their skin annually. Street (1952)
also believed Cyclura nubila on Cuba shed only once a year (during the
spring).
The onset of shedding in Cyclura carinata seems to be coincidental
with the resumption of more rapid growth following the cold and dry
winter. The skin is not sloughed rapidly; ecdysis may require several
7+- 13/9
7 4
6
5-
3
z 2-
Z
N
1 3 5 7 9 11 13 15 17
SPINE HEIGHT [mm]
FIGURE 35.-Relationship of mean maximum dorsal back (B) and neck (N) spine heights
to number of spine annuli in male Cyclura carinata. Numbers adjacent to curves are
sample sizes.
1979
BULLETIN FLORIDA STATE MUSEUM
months for completion. The skin of the head and upper trunk areas are
shed first, followed by the lower trunk, then the limbs and ultimately
the tail. In those instances where traces of paint were still visible dur-
ing late summer or autumn on lizards marked the previous year, the
paint remnants were always on the tail or distally on the limbs. Once
initiated, juvenile shedding appeared more rapid than that of adults,
as would be expected from the more rapid juvenile growth rate.
Because there is evidence that ecdysis is an annual phenomenon,
the annuli on the dorsal spines are believed to represent yearly in-
crements. Since annulus counts are therefore approximately equal to
age post-maturity in male lizards, growth rate can be estimated by
comparing these counts to lizard size. Figure 37 demonstrates the
linear relationship between number of spine annuli and body length in
Cyclura carinata. The least-squares regression equation for this data (y
= 0.59x 11.849) indicates an SVL change of approximately 1.7 cm
with the addition of 1 annulus, i.e. 1 year. This is equivalent to a
growth rate of 1.41 mm SVL per month, more than twice the 0.66 mm
estimate for young adult males and only slightly less than the 1.85 mm
estimate for juveniles based on actual recaptures. SVL lengths
calculated from weights recorded from six captive adult male lizards
by David Auth (pers. comm.) for periods totaling almost 60 months
(Range 7.25 to 14) exhibited an average monthly change of 1.82 mm.
20
E 15 'MN
XI-6
10 3. 5 / 6 MB
ILl 3 2 3
Z 5 MT
m 5 2
1 7 5 1
20 22 24 26 28 30 32 34 36
SVL [cm]
FIGURE 36.-Change in dorsal spine height with body size in Cyclura carinata. Means
for maximum spine heights from neck (MN), back (MB), and tail spines (MT) of males
and neck spines of females (F) are plotted by 1 cm body size classes. Numbers adjacent
to curves are sample sizes.
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
This presumably overestimates actual growth rate, since captive
animals receive more food of higher quality than do wild individuals.
Therefore, the actual adult male growth rate is probably close to the
1.41 mm per month estimate from the annulus data.
Due to small sample sizes, it was impossible to relate social status
to growth rate in wild populations. However, in captivity, subordinate
male lizards (females do not exhibit dominance relationships in nature
or captivity, except during nesting) often would not eat even when
food was abundantly available. In addition, their activity was greatly
reduced. Berry (1974) found that dominant male Sauromalus grew
more rapidly than subordinates, and I suspect a similar relationship in
wild male Cyclura carinata. Males unable to establish territories in
primary habitat are forced to occupy inferior peripheral habitats, such
as unstable sandy habitats. As an example, the distal two-thirds of the
sand spit formed since 1967 at the northeast point of Little Water Cay
is populated only by adult male lizards.
If the juvenile growth rate (through 6 yr) is 1.6 mm per month, as
indicated by the Little Water Cay recapture data as well as age-size
class analysis, and the adult male rate (after 6 yr) is 1.4 mm per month,
the average adult male of 276 mm SVL (Table 8) is approximately 10
yr 10 mon of age.
Unfortunately growth rates of adult females are not so readily
calculable. However, if a female lizard of mean adult female body size
(225 mm SVL; Table 8) is the same age as a male of mean body size, an
increment of monthly growth in adult females of 0.52 mm is indicated.
+* *
7 6
6-
5-
-4
:3
Z 3
Z 2 .
0* *
20 22 24 26 28 30 32 34 36
SVL (cm)
FIGURE 37.-Change in number of neck spine annuli with body size in male Cyclura
carinata. Back spine annuli number is two less than neck spine count. Small dots in-
dicate individual records; large dots, two or more. Least squares regression (y = 0.59x
- 11.849; N = 34; r = 0.8577; p = p< 0.01) utilizing only that data for annuli number-
ing through seven is plotted.
BULLETIN FLORIDA STATE MUSEUM
It remains to be seen whether this assumption is a valid one. In any
case, this estimate supports the rate determined from four recaptured
adult females (0.36 mm/month).
SVL lengths calculated from weights recorded from four captive
female lizards by David Auth (pers. comm.) for periods totaling more
than 53 months (range, 7.25 to 26) indicated an average monthly in-
crease of 1.11 mm. This value is over two times the estimated natural
growth rates. One captive female gained 63 mm in SVL (and 562 gm
body weight) in only 26 months (2.42 mm/mon). A similar-size female
marked and recaptured on Little Water Cay gained only 3 mm over 24
of the same 26 months. This accelerated captive growth may indicate
that natural food resources are limiting growth (see FOOD AND
FEEDING).
From the SVL-body weight and the SVL-spine annuli regressions,
calculated annual adult male weight changes constantly increase from
about 14 gm/yr in newly maturing individuals to almost 24 gm/yr in
older lizards (X = 18.9 3.1, from ages 6 to 17 yr). Calculated yearly
weight increases were 82 gm/yr during the sixth year and 252 gm/yr
during the sixteenth year.
The slowing of the growth rate in adult females when compared to
males is perhaps related to the high annual female reproductive expen-
diture; female Cyclura carinata deposit roughly 25% of their gravid
body weight annually when nesting (see REPRODUCTION). Apply-
ing the SVL-body weight regression to the mean adult SVL for males
(276.26 mm) and females (225.9 mm) calculates body weight at 815 gm
and 440 gm, respectively. Age for males of this size was previously
determined to be approximately 10 yr, 10 mon. Six-year-old subadult
lizards average 195 mm SVL and 283.5 gm. Therefore, males increase
their weight 531.5 gm in 4 yr, 10 mon. If we assume average-size adult
females are also aged 10 yr. 10 mon, then they experience only a 156.5
gm increase in the same 4 yr 10 mon. (Even if this is not a strictly valid
assumption, I believe its accuracy will not greatly affect the following
discussion.) However, in that period of time, a female would have
deposited five clutches of eggs. Since mean clutch size for females 195
to 225 mm SVL equals 3.42 and mean egg weight equals 25.9 gm,
average clutch weight for those five clutches is approximately 88.6
gm. Add the weight of five average clutches (442.9 gm) to the 156.5 gm
female increase during the 4 yr, 10 mon and we observe that a poten-
tial weight increase of nearly 600 gm might be possible if reproductive
output were rechanneled to growth (and maintenance costs were
disregarded).
It is perhaps more than coincidental that this value is approximate-
ly equivalent to the male increase during the same five periods (531.5
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
gm). It is tempting to suggest that the observed sexual size dimor-
phism is explainable in terms of a simple shift of a portion of the poten-
tial energy available for growth to use in the reproductive output of
females. Nevertheless, it would probably be better explained as a
means of reducing intraspecific competition and/or as a correlate of the
polygynous mating system.
FACTORS AFFECTING GROWTH
As shown above for juveniles, lizards grow little during the winter.
This is probably due primarily to two factors. In response to the colder
and drier conditions most plant species do not produce fruits or
flowers. Cyclura must necessarily become more folivorous. Since diges-
tion of fibrous leaves is presumably more difficult, as evidenced by the
fact that leaves often pass through the entire gastrointestinal tract
unaltered, and the caloric content of leaves is generally lower than that
of fruits (Golley 1969; Auffenberg MS), the nutritive quality of the
winter diet is much reduced. Secondly, lower winter environmental
temperatures sometimes make it impossible for lizards to reach pre-
ferred temperatures for one to several days at a time. Feeding is
therefore precluded, and digestive activity is presumably reduced
(Harlow et al. 1976) as most activity certainly is. Thus, despite their
tropical location, populations of Cyclura carinata are subjected to a
distinct climatic seasonality which is reflected in a decrease in the
physical and physiological availability of the food resources during the
winter. Growth must necessarily slow during that period.
LONGEVITY
If the previously estimated adult male growth rate (17 mm/yr) were
maintained from age 6 yr (195 mm SVL) on, with no slowing in old age,
it would require over 15 years to reach the approximate 350 mm max-
imum male SVL. Even if the mean juvenile growth rate was main-
tained throughout life, over 14 years would be required for a male to
reach that 350 mm maximum SVL. These data suggest that large
adult males commonly live 15 yr; many probably live 20 yr, with occa-
sional individuals surviving 25 yr.
REGENERATION
As in most other lizards (Fitch 1954:97; Tinkle 1967b:58), rate and
extent of tail regeneration in Cyclura carinata is dependent on a varie-
ty of factors, including age and site of fracture. Figure 38 illustrates
the relationships of tail break site in juveniles, females, and males on
the total length of tails with regenerated portions. The data indicate
that: (1) fully regenerated tails in juveniles are proportionately longer
1979
BULLETIN FLORIDA STATE MUSEUM
than those of adults, and (2) the longer the lost tail segment, the
shorter the completely regenerated tail length will be.
Information on actual regeneration rates of broken tails is scanty
and only data from juvenile lizards are available. Regeneration is very
rapid in juveniles, exceeding 5 mm per month (maximum recorded 7.3).
The fact that the majority of the broken-tailed adult lizards seen ex-
hibited nearly maximal regeneration (note modal values in Fig. 38)
*
J F M
J F M
J F M
I
REGION
UI
OF TAIL BREAK
FIGURE 38.-Proportional tail length (TL x 10/SVL) in broken-tailed Cyclura carinata
for juveniles (J), females (F), and males (M), based on region of break. Roman numerals
refer to break position: I = proximal third unregeneratedd portion of tail/SVL = 0 to
0.47), II = Middle third (0.47 to 0.93), and III = distal third (over 0.93). Data from tails
with multiple breaks are not plotted. Unbroken tails have a mean proportional length of
about 14.
in
_ I I I I I I I I
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
suggests that regeneration rates in adults are also very rapid. The im-
portance of the tail for balance when running, and as an escape
mechanism from predators, as well as its use in social contexts (see
SOCIAL ORGANIZATION) bespeaks the selective value of rapid tail
regeneration.
Occasionally incompletely severed tails will begin regeneration,
producing forked tails. In this study, three lizards were encountered
with bifurcate tails; one additional iguana exhibited three tail forks.
COMPARISONS WITH OTHER IGUANINES
Cyclura carinata is a medium-sized iguanine lizard; the genera
Brachylophus (one species), Ctenosaura (four species, except C. similis)
Enyaliosaurus (four species), and Sauromalus (five species), and only
one other species of Cyclura (rileyi) are smaller. Cyclura carinata ex-
hibits greater sexual size dimorphism than any other iguanine (see
above); adult females average only about 80% and 50% of adult male
SVL and body weight, respectively. Male Cyclura pinguis are also
larger than females (Carey 1975) but not to the extent found in C.
carinata.
A juvenile growth rate of 1.6 mm SVL/mon (0.052 mm/day) in
Cyclura carinata is among the slowest yet recorded among lizards (see
review in Tinkle 1967b). This is undoubtedly an artifact of the much
greater size of juvenile Cyclura compared to previously studied
juvenile lizards. Comparisons of weight changes during juvenile
growth are probably more meaningful to growth discussions involving
lizard species of greatly varying sizes. Unfortunately, these data are
not easily extracted from the literature. Nevertheless, the rates of
body length change for juvenile Cyclura carinata compare favorably
with those recorded for other juvenile iguanines (Table 11). Adult
growth rates are similarly congruent (Table 12).
Very little information exists on age at maturity in iguanine
lizards. Fitch (1970) theorized that three years is the minimum
breeding age for Ctenosaura similis in Costa Rica. Mayhew (1971),
Berry (1974), and Carey (1975) similarly postulated that Dipsosaurus
dorsalis, Sauromalus obesus, and Cyclura pinguis require 5-6, 9, and
7-9 yr respectively. These data correspond well with my estimate of 6-7
yr for Cyclura carinata and Wiewandt's (1977) estimate of 6-7 yr for C.
cornuta.
Longevity has been discussed previously for few iguanine species.
Johnson (1965) and Berry (1974) postulated 25 and 20 years, respec-
tively, as estimates of longevity for Sauromalus obesus in the Mojave
Desert. Carey (1973) maintained two Dipsosaurus dorsalis (adults
when obtained) in captivity for just over 14V2 years; assuming at least
1979
263
BULLETIN FLORIDA STATE MUSEUM
TABI.E 11.-JUVENII,.: GRowTni RATES IN I;GUANINE LIZARDS.
Species Location
Ctenosaura Western Costa
similis Rica
Ctenosaura Belize
similis
Ctenosaura Western Costa
similis Rica
Cyclura Caicos Islands
carinata British West
Indies
Cyclura Mona Island
cornuta
Cyclura Anegada, British
pinguis Virgin Islands
Dipsosaurus California
dorsalis
Dipsosaurus Arizona
dorsalis
Iguana Belize
iguana
Sauromalus California
obesus
Sauromalus California
obesus
Sauromalus California
obesus
Growth
rate (mm Sample
SVL/month) Size Data Base
9
9
9 2+ age class
groupings
.17 1 age class
groupings
.86 8 field recaptures
(7.5 to 15.33)
1.6 206 age class
groupings
1.74 16 field recaptures
2.10 8 captive data
4.4 8 captive
6 noncaptive
1.2 and 3.0
2 captives
0.8 to 4.4* 23 captive
0.9 to 1.2* ? field recaptures
2.7
(0.0 to 5.1)
6.60
o =3.8
(1.6 to 6.3)*
9=1.8
(0.0 to 4.2)*
2.5'
22 field recaptures
23 field recaptures
21 field recaptures
15 field recaptures
1 field recapture
3.5 1 captive
Reference
Fitch 1970
Henderson 1973
Fitch 1973
Present study
Wiewandt 1977
Carey 1973,
1975
Mayhew 1971
Parker 1972
Henderson 1974
Berry 1974
Johnson 1965
Mayhew 1963a
*Growth rates for growth season of six months only.
five years to reach adulthood (Mayhew 1971), at death the lizards were
probably more than 20 years of age. Goin and Goin (1962) considered 15
yr to be the maximum age for Conolophus subcristatus, and Mueller
(1968, 1972) believed that very few Iguana iguana lived more than 10 yr.
Iguanine lizards of at least 13 species (including four species of Cyclura),
each wild-caught as an adult, have been maintained in captivity from 4
to 17 yr (review in Bowler, 1977). Unfortunately Carey (1975) did not
speculate on longevity for Cyclura pinguis in the British Virgin Islands.
However, if longevity is computed by utilizing his values for size (400
mm) and age (7-9 yr) at sexual maturity, maximum size (about 540 mm),
Vol. 24, No. 3
264
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
TAiI.: 12.-A)u:L'. GitOWTii RATES OV I(;UNIN: LIZAIzIS. Asre:IISK INI)ICATIS G IOWrII
I(ATrI:Es FO Six MONTH GIOWTrII SEASON ONI.Y.
Species Location
Sauromalus California
obesus
Cyclura Caicos Islands
carinata British West
Indies
Sauromalus California
obesus
Growth rate
(mm SVL/month)
0-1.7
1.6
0.5-1.3
0.18
(<270 mm SVL)
0.66
1.41
1.82
0.36
1.11
(<170 mm SVL) 1.9
(0-4.3)*
(>170 mm SVL) 0.7
(0-2.3)*
(<170 mm SVL) 0.3
(0-0.5)*
(>170 mm SVL)-
0.04
(0-0.1)*
Sample
Size
Data Base Reference
8 field recaptures Johnson
1 captive 1965
11 field recaptures
12 field recaptures Present
4 field recaptures study
34 spine annuli
analysis
6 captives
4 field recaptures
4 captives
14 field recaptures Berry
1974
31 field recaptures
6 field recaptures
19 field recaptures
and the average of his two captive subadult growth records (2.1
mm/month), a minimum longevity of nearly 14 yr is obtained. Follow-
ing a similar procedure, Cyclura carinata must normally live from 15
to 20 yr.
FOOD AND FEEDING
DIET
GENERAL COMMENTS.-Food items eaten by Cyclura carinata are
listed in Tables 13 and 14. A more comprehensive analysis of diet,
based on stomach analysis, appears in Auffenberg (MS); therefore,
only a few important points regarding diet are discussed here.
At least 95% of the diet (in volume or numbers of items) of lizards
of all ages during all seasons is plant material (Auffenberg MS; this
study). As expected, seasonal diet variation reflects food availability;
fruits and flowers are necessarily infrequently represented (leaves fre-
quently) in the winter diet. Ontogenetic diet changes are primarily
related to the increasing size of the trophic apparatus with age; adults
are more efficient leaf-croppers and can swallow much larger fruits
than juveniles.
Strumpfia (bay cedar) is the single most important food item in the
diet of Cyclura carinata during the first year of its life. Erithalis (Torch
1979
TABLE 13.-PLANTS KNOWN TO BE EATEN BY Cyclura carinata on Pine Cay. Fecal Determinations by Gross Examination Only.
Discovered
Species Leaves Fruits Flowers Other In GI tract In feces By observation
Acacia acuifera ++ X X
Ambrosia hispida X
Amyris elemifera -- X
Andropogon glomeratus X X
Antirhea myrtifolia -- + X X
Argythamnia sericea X
Bourreria ovata X X
Bucida buceras --X
X 0
Bumelia americana -
Byrsonima cuneata -- + X X
Calyptranthes pallens + X X X >
Casasia clusiaefolia + -- X X
Cassia lineata -- X X
Catesbaea foliosa - X
Chamaesyce buxifolia --X
Chamaesyce vaginulata -- -- X
Chloris petraea + + X X X
Coccoloba krugii ++ X X X
Coccoloba uvifera -- ++ X X X
Conocarpus erectus X X X
Crossopetalum rhacoma -- + X X X
Cuscuta americana --X
Cynanchum cf eggersii X
Cyperus fuligineus + X X
Digitaria filiformis + + X X
Erithalis fruticosa + ++ + flower X X X
buds P
S.. ... Y X o
++ I
Ernodia millspaughii
Eugenia foetida
Evolvulus sp.
Guaiacum sanctum
Guapira obtusata
Guettarda krugii
Gundlachia corymbosa
Hippomane mancinella
Hypelate trifoliata
Jaquinia keyensis
Manilkara bahamensis
Maytenus buxifolia
Metopium toxiferum
Paspalum laxum
Phyllanthus epiphyllanthus
Pithecellobium guadelupense
Plumeria obtusa
Psidium longipes
Rachiallis americana
Reynosa septentrionalis
Rhizophora mangle
Scaevola plumieri
Strumpfia maritima
Tabebuia bahamensis
Thrinax microcarpa
Thyralis sp.
Tournefortia volubilis
Zizyphus taylori
2 mushroom species
6 unidentified species
No'l:: -- occasional
+ common
+ + abundant
leaf buds
shoots
shoots
leaf buds
and petioles
+ stems
+ ++
-- flower buds
(entire plant)
+
BULLETIN FLORIDA STATE MUSEUM
TABLE 14.-ANIMALS KNOWN TO BE TAKEN BY Cyclura carinata ON PINE CAY.
Discovered
In In By
GI Tract Feces Observation
Mollusca
unidentified slug X
Crustacea
Decapoda
Clibanarius (hermit crabs) X X X
Cardisoma guanahumi (land crabs) X X
Insecta
Homoptera
Ollanta caicosensis (Cicada) nymphs X X
Ollanta caicosensis (Cicada) adults X X
Lepidoptera
Pseudosphinx tetrio larvae X
Hymenoptera
unidentified honeybee X
Isoptera
Nasutitermes costatus X
Coleoptera
unidentified adult weevils X
unidentified beetles X X
Diptera
unidentified species X X
Odonata
unidentified wing fragments X X
Arachnida
Solpugidae X
Reptilia
Cyclura carinata juveniles X X
Cyclura carinata skin X X
Aves
various species (as carrion) X
unidentified feathers X X
wood) and Ernodea (guanaberry) are also very important. Of 6
neonates captured in September with food in their gastrointestinal
tracts, 5 had eaten Strumpfia fruits, and two contained Erithalis
and/or Ernodea in their digestive tracts. During December of their
first year (approx. age, 3.5 mon), 7 of 12 juveniles had fed on Strump-
fia, and 3 of 12 had eaten more than one of these three species. By
March (age 61/2 mon), each of 4 juveniles had eaten at least one of the
Vol. 24, No. 3
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
three species; by June and July (age, 9-10 mon) this proportion was 2 of
6. This may reflect the occurrence of the three plant species in nearly
all habitats, as well as the fact that fruit is produced throughout an ex-
tended reproductive season (Auffenberg MS; pers. observ.).
In addition to fruits of the above three species, adults are especially
fond of fruits of Antirhea, Casasia, Coccoloba, Eugenia, Manilkara,
Psidium, Reynosa, and Thrinax. Evidence of the fruits of at least one
of these species was found in the gut of nearly every adult lizard
dissected.
GEOPHAGY.-The guts of nearly all Cyclura carinata examined con-
tained sand grains and/or other soil fragments. There is some con-
troversy as to whether reptilian geophagy and/or lithophagy is inten-
tional or accidental (see Kennedy and Brockman 1965; Sokol 1967; for
literature review). Despite Sokol's (1971) observations (in captivity?)
of apparently intentional geophagy in the iguanines Iguana iguana
and Ctenosaura pectinata, I believe that Cyclura carinata does not pur-
posely ingest particles of the substrate. I have never observed
geophagy in this species either in captivity or in the field.
COPROPHAGY.-The intentional ingestion of feces, whether from
their own or other species, has been documented for herbivorous tor-
toises (Auffenberg and Weaver 1969; Mares 1971) and has been
reported in the herbivorous lizards Amblyrhynchus cristatus (Wilcox
et al. 1973, bird feces), Dipsosaurus dorsalis (Norris 1953; Stebbins
1954; Minnich and Shoemaker 1970, mammal and reptile, including
their own), Iguana iguana (Swanson 1950, believed by natives to eat
human excrement), Sauromalus obesus (Nagy 1973, fecal origin
unspecified; Sanburn 1972, Neotoma lepida droppings), and
Utomastix acanthinurus (Dubuis et al. 1971, gazelle drippings).
However, feces were not found in the upper gastrointestinal tracts of
any Cyclura carinata dissected.
The importance of coprophagy to iguanines is unknown. Unfor-
tunately Nagy (1973) did not speculate on the significance of the occur-
rence of feces in the stomachs of Sauromalus. Mares (1971) hypothe-
sized that ingestion of the scats of herbivores by other herbivores
might increase the latter's efficiency of assimilating the contained
cellulose materials since they are already partially digested. Minnich
and Shoemaker (1970) suggested that the ingestion of fecal materials
may provide specific nutritional requirements (vitamins and proteins)
otherwise lacking in a plant diet. Another possible benefit of
coprophagy is that it provides a means of acquiring potentially sym-
biotic intestinal micro-organisms that might also increase assimilation
efficiencies (see Digestive Efficiency, this section, and IN-
TERSPECIFIC COACTIONS).
1979
BULLETIN FLORIDA STATE MUSEUM
CANNIBALISM.-The inclusion of conspecifics in the diet of Cyclura
carinata is of particular interest (Table 14): cannibalism is extremely
rare among iguanid lizards, especially in non-captive situations (Burt
1928; Dodge 1938; Shaw 1950; Mayhew 1963c; C. Johnson 1965; Mon-
tanucci 1965, 1976; Groves 1971; Bowie 1973). No herbivorous lizard is
known to exhibit cannibalism in nature; but Alvarez del Toro (1972)
reported that Ctenosaura similis in captivity will eat "young iguanas"
(species not given). However, a hatchling C. carinata was found in the
stomach of a conspecific adult female (203 mm SVL) collected near the
Ridge Area on Pine Cay on 2 January 1974.
In addition one natural observation of possible cannibilism was
made. On 3 September 1974, while walking along a trail near the SW
Blind, I flushed a hatchling Cyclura from a low perch near the trail's
edge. He ran away from me into the bush, directly toward an adult
male that he had apparently not seen. As the hatchling ran to within
1.5 m of the male, the adult charged and snatched the hatchling up in
his mouth by its entire left foreleg. As the hatchling flailed in an at-
tempt to escape, the male vigorously shook it. I stooped to get a better
view, and frightened the adult, which ran off out of sight with the
hatchling dangling in his mouth.
EPIDERMOPHAGY.-Shed skin is commonly found in the
gastrointestinal tracts and/or feces of Cyclura carinata. Murphy (1969)
observed Cyclura cychlura in captivity to pull shedding skin from
other iguanines and feed on it, but in my study ingestion of skin was
not observed in either wild or captive C. carinata. Of 54 adult iguanas
dissected, 12 had skin fragments in their guts; 9 of those were females
and 3 were young males (222-298 mm SVL). A shed male dorsal spine
was found in the large intestine of another female. These observations
suggest that females groom dead skin from males. Of all records of
skin in guts or feces, 80 percent fell between 5 March and 13 August.
The adaptive significance of epidermophagy in reptiles is unknown;
Bustard and Maderson (1965) reviewed the subject and speculated
that, as in birds and mammals (Rawles 1960; Mercer 1961), the in-
gested skin represents an alternative source of Vitamin D.
CARRION FEEDING.--Cyclura carinata do not hesitate to feed on car-
rion when it is encountered. They are, in fact, attracted to carcasses by
olfactory clues. I have observed iguanas locate and feed on the decay-
ing soft part of hermit crabs. On several occasions birds shot for diet
analysis and not immediately retrieved were found by foraging ig-
uanas. In every case, the lizard immediately began feeding on the car-
cass. (See example under Social Feeding). Fish carrion was found in the
stomach of one iguana. Several-day-old canned sardines were con-
sumed as readily as fresh ones at the SW Blind.
Vol. 24, No. 3
270
IVERSON: ROCK IGUANA BEHAVIOR-ECOLOGY
Among iguanines, carrion feeding has been reported for Iguana
iguana (Loftin and Tyson 1965) and Dipsosaurus dorsalis (Norris
1953). I suspect necrophagy is more common among iguanine lizards
than the literature suggests.
COMPARISONS WITH OTHER IGUANINES.-An extensive literature,
supplemented by dissections of previously unstudied forms, indicates
that all 30 species of the subfamily Iguaninae are primarily her-
bivorous throughout their lives. Some iguanid and agamid species are
believed to exhibit an ontogenetic change from carnivory to herbivory
(Mertens 1960; Pope 1969; Fleet and Fitch 1974; Carey 1975; Fitch and
Henderson 1977a; and review in Pough 1973), but this definitely is not
the case in Cyclura carinata. Unfortunately, captive and anecdotal
natural observations form the basis for suggesting this strategy for
other iguanine species (Iguana iguana, Amblyrhynchus cristatus, and
most species of Cyclura). Further study is necessary to determine
whether the juveniles of other iguanines (or any other herbivorous
lizards) ingest animal matter opportunistically or intentionally. Table
15 reviews the literature on diet in the genus Cyclura. Fruits of such
widespread forms as Coccoloba, Erithalis, and Opuntia are probably
eaten by iguanas wherever they co-occur. Auffenberg (MS) compares
breadth of the food niche with respect to floral diversity within the
genus Cyclura.
FEEDING BEHAVIOR
GENERAL COMMENTS.-Cyclura carinata will feed anywhere within
its home range (see ACTIVITY AND MOVEMENTS), but males feed
within their defended territories more often than outside them (see
SOCIAL ORGANIZATION). Feeding activity is bimodal during the
warmer months (because of high midday environmental temperatures)
and unimodal during colder months. Lizards generally make one to
several feeding forays away from their burrows each day. During the
winter only one foray is usually possible. Weather permitting, iguanas
will feed every day of the year (see ACTIVITY AND MOVEMENTS).
Hatchling lizards begin feeding soon after emergence from the nest.
Of seven neonates collected on 18 September 1973, six contained food
both in the stomach and intestines. Others collected 30 August 1974
(4), 31 August 1974 (2), and 5 and 8 September 1975 (1 each) either
lacked food in the gut or produced no scats following capture. Of all
the lizards examined, these were the only ones that lacked digesta in
the gastrointestinal tract.
As in Iguana (Rand 1967b) and Dipsosaurus (Norris 1953), feeding
may also be reduced in female Cyclura carinata carrying eggs. The en-
tire gastrointestinal tract of a gravid female dissected 3 June con-
TABLE 15.-NATURAL FOODS RECORDED FOR LIZARDS OF THE GENUS Cyclura.
Species Location Diet' Reference
Jamaica
Mona Island
Mona Island
C. collei
C. cornuta
C. cornuta
C. cornuta
C. cornuta
C. cychlura
C. nubila
C. nubila Cayman Brac
C. nubila Cayo de la Piedra, Cuba
C. pinguis Anegada B.V.I.
C. pinguis Anegada
C. pinguis Anegada
C. ricordi Dominican Republic
Petiveria sp. (leaves)
Tribulus cistoides
74 species of vascular plants including fruits of 26 species; flowers
eaten when available
Sphingid moth larvae
Scarab beetles
"fruits", crabs
cactus fruits
Erithalis fruticosa (flowers, buds, & leaves)
Ipomoae pes-caprae (flowers and leaves)
Cordia caymanensis
Ernodea littoralis
plums, mangoes
Opuntia (all parts)
crabs
Coccoloba (leaves)
Opuntia (fruit)
nutmegss"
Cactus (all parts)
Coccoloba
Conocarpus erectus (leaves)
Reynosa uncinata
Erithalis fruticosa
Coccoloba uvifera (leaves)
Unidentified grasses
Lantana reticulata
Insects (mainly Lepidopteran larvae)
Pisonia rotundata
cactus fruits
'Items in diet are listed in approximate decreasing order of useage. Plant parts (leaves, fruits, etc.) are included when possible.
Hill in Gosse 1848
Martin 1966
Wiewandt 1977
Eyerdam 1954
Carey 1975
Wilcox et al. 1973
Grant 1940b
Grant 1940b
Sutcliffe 1952
Grant 1937
Underwood 1962
Carey 1975
0,
Carey 1975 z
o
C',
Haiti
Dominican Republic
Exumas, Bahamas
Little Cayman Island
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