|
of the
FLORIDA STATE MUSEUM
Biological Sciences
1988
Number 4
ECOLOGY OF THE BOBCAT IN
SOUTH-CENTRAL FLORIDA
Douglas A. Wassmer, Del D. Guenther,
and James N. Layne
UNIVERSITY OF FLORIDA
Volume 33
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ECOLOGY OF THE BOBCAT IN
SOUTH-CENTRAL FLORIDA
Douglas A. Wassmer, Del D. Guenther, and James N. Layne*
ABSTRACT
The ecology and life history of the bobcat (Felis nifiis) were studied on the protected
Archbold Biological Station and surrounding semi-developed land in south-central Florida from
1979 to 1982. Mean densities were 5 adult males, 8 adult females, and 13 juveniles/100 km .
Overall adult sex and age ratios were 0.64 male/female and 1.00 juvenile/adult, respectively.
Breeding occurred from August to March, with a peak in February and March. The mean size of
13 mobile litters was 2.6. Of 17 radio-collared cats, 9 died during the study, and 9 unmarked
individuals were found dead or reported killed in the study area. A higher proportion of
mortality (73%) was due to natural (feline panleucopenia and Notoedric mange) than to
man-related causes. Cottontail rabbits (Sylvilagus floridanus), marsh rabbits (S. palustris), and
cotton rats (Sigmodon hispidus) were the primary prey species, comprising 73% of the
occurrences of food items in scats and 86% of estimated prey biomass. Overall home ranges of 5
adult males and 7 adult females averaged 25.5 km and 14.5 km respectively. Short-term home
ranges during 12 intervals of 3 to 16 weeks averaged 14.5 km for males and 9.3 km for females.
Females tended to use their home ranges more intensively than did males, but males moved
farther from day to day than females. One adult female and one male adult were known to
abandon their ranges, the female's range apparently being acquired by her male and female
young. Adults of the same sex had non-overlapping home ranges, but ranges of males and
females overlapped extensively. Adult males and females with shared home range areas
occasionally travelled or rested together in all seasons. Activity was primarily crepuscular and
nocturnal. Seasonal variation in activity of males appeared to be related to temperature and in
females to care of young. Both sexes used natural vegetation types more than man-modified
habitats, with males using man-modified habitats relatively more than females. Marking behavior
varied seasonally and appeared to play a significant role in maintenance of home range
boundaries of adult males and adult females. Compared with data from other parts of the range,
the south-central Florida population had an average density comparable to values reported from
* Douglas A. Wassmer and Del D. Guenther conducted phases of this study for their M.S. degrees in the Department of
Biology, University of South Florida, Tampa, Florida 33620. Their current addresses are: (DAW) 5106 Vinson, Tampa, Florida
33610; (DDG) N. 4220 Bessie Road, Spokane, Washington 99212. James N. Layne is Senior Research Biologist, Archbold
Biological Station, P. 0. Box 2057, Lake Placid, Florida 33852.
WASSMER, D.A., D.D. GUENTHER, and J.N. LAYNE. 1988. Ecology of the Bobcat in
South-central Florida. Bull. Florida State Mus., Biol. Sci. 33(4):159-228.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
elsewhere in the southern U.S. and somewhat higher than levels recorded in northern areas;
relatively low litter size; comparatively small home range size; and a possibly higher frequency of
cases of a single adult female range contained entirely within an adult male range suggestive of a
facultative monogamous relationship. Implications of the study to conservation and management
of bobcats are discussed.
RESUME
Se estudiaron la ecologia y historic natural del gato months (Felis nifa) en la protegida
Estaci6n Biol6gica de Archbold y en areas adyacentes semidesarrolladas en el centro-sur de
Florida, de 1979 a 1982. Densidades medianas eran de 5 machos adults, 8 hembras adults, y 13
juveniles por 100 km 2. Las relaciones de sexo adulto y de edad eran 0.64 macho/hembra y 1.00
juvenil/adulto, respectivamente. Habia reproducci6n de agosto a marzo, con el maximo en
febrero y marzo. El tamafio median de 13 crias m6viles era 2.6. De 17 gatos marcados con
radio-collares, murieron 9 durante el studio, y se encontraron o se informaron de otros 9
individuos muertos en el area. La mayor parte de la mortandad (73%) se debia a causes
naturales (panleucopenia felina a sarna noto6drica), y no a actividades humans. Conejos
(Sylvilagus floridanus y S. palustris) y ratas de algod6n (Sigmodon hispidus) son las press
principles, formando 73% de las occurrencias en heces, y 86% de la biomass calculada. A base
de 5 machos adults y 7 lembras adults, los promedios de territories totales eran de 25.5 km2
para machos y de 14.5 km para hembras. A corto plazo, durante 12 periods de 3 a 16 semanas,
los territories promedios eran de 14.5 km para machos y de 9.3 km para hembras. Las hembras
suelen usas sus territories mas intensivamente, mientras que los machos viajan mas de dia a dia.
Una hembra adulta y un macho adulto abandonaron sus territories durante el studio, el
territorio de la hembra aparentemente pasando a sus hijos. Los territories de adults del mismo
sexo no traslapan, pero los territories de machos y hembras traslapan extensivamente. Machos y
hembras adults con territories compartidos viajan o descansan juntos de vez en cuando en todas
las estaciones. La actividad es principalmente crepuscular y nocturna. Variaci6n estacional en
actividad se relaciona con la temperature en los machos y con el cuidado de la cria en las
hembras. Ambos sexos usan ambientes de vegetaci6n natural mAs que ambientes modificados
por el hombre, con los machos usando ambientes modificados relativamente mAs que las
hembras. El comportamiento de demarcar territorio varia con las estaciones y parece jugar un
papel significant en mantener los limits territoriales de machos y hembras adults. Comparada
con datos de otras areas, la poblaci6n del centro-sur de Florida tiene una densidad median
comparable con otras areas del sur de los EE.UU. y algo mas alta que las densidades encontradas
en areas nortefias; crfa relativamente pequefia; territorio relativemente pequefio; y posiblemente
mayor frecuencia de tener el territorio de una hembra adulta enteramente dentro del territorio
de un macho adulto, sugieriendo una relaci6n mon6gama facultativa. Se discuten las
implicaciones del studio para la conservaci6n y el manejo de la especie.
TABLE OF CONTENTS
Introduction.......................................................................... .......................... 161
A cknowledgem ents................................ ......................................................... ........................ 162
Study A rea.......................................................................................................... ................................... 163
M methods .................................................................................................................................................... 167
Capture and H andling..................................................... .................................................. 167
Subjects........................................................................................................... ......................... 167
Study T echniques.............. ........................................................................................................ 169
D ata A nalysis................................. ........................................................ ......................... 170
R results and D iscussion............... ..................................................................................................... 171
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 161
Capture Success............................ ......................................................... ........................ 171
Demographic Characteristics................. ................................................................. 173
D density .................................................. ......................... .................................................... 173
Sex and A ge R atios ................................ ............................................................................ 173
B reading Season ............................................................ ................................................... 175
N atality......................................................................... .. ........................ 175
M ortality and Injuries....................... ............................................................................ 176
Longevity ................................................................. .. ......................... 181
F ood H ab its ............................................................................................................................. 181
Home Range and Social Organization.......................................................................... 184
H om e R ange Size........................................................... .................................................. 184
Use of Area Within Home Ranges.............................................. ............................. 189
Relationships Between Adult Home Ranges............................... ............................ 189
Female-Young Behavior and Home Range Use........................... ............................ 198
D aily T ravel ......................................... ..................................................................................... 205
A activity .......................................................................... ........................ 208
H ab itat U se.................................................... ..................................... ............................... 2 12
M parking B behavior .................................................................................. .................................. 217
Frequency of Types of Marking Behavior.................... ...... ............................ 217
Seasonal and Yearly Variation in Marking.................................. ............................ 217
Spatial Patterns of Marking Behavior................................................ ......................... 220
Conservation and Management Implications............................................ ............................. 223
L literature C ited ....................................................................................................................................... 225
INTRODUCTION
Previous studies of the bobcat (Felis nifits) in the southeastern United
States (e.g. Buie et al. 1979, Hall 1973, Kitchings and Story 1979, 1984,
Marshall 1969, Miller 1980) and in other parts of North America (e.g. Bailey
1972, 1974, 1979, Lawhead 1978, Zezulak and Schwab 1979) have revealed
considerable geographic variation in habitat relationships, movement patterns,
population levels, and other aspects of the species' ecology and behavior. Such
variability emphasizes the need for basic ecological and life history data from
many populations throughout the bobcat's range in order to gain a more
complete understanding of the basic biology of the species and its role in
natural and man-modified ecosystems. Increasing pressure on the bobcat by
the fur trade (National Wildlife Federation 1977) together with habitat loss in
many parts of the range also have created a need for more detailed
information on population dynamics, habitat requirements, and other
ecological and life history parameters of regional populations to provide the
basis for more effective management.
Although numerous references to local distribution and general habits of
the bobcat appear in the published literature on Florida mammals, there have
been few detailed studies of specific aspects of its biology in the state. The
principal objective of this study was to obtain baseline data on demographic
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
characteristics, home range, movements, activity patterns, habitat use, food
habits, social organization, and marking behavior of the bobcat in south-central
Florida. The study area consisted of a core area of completely protected
natural habitat surrounded by a semi-developed area typical of many parts of
Florida. This configuration allowed comparison of mortality rates and certain
other life history parameters in natural versus variously man-modified habitats.
Although bobcats in the part of the study area outside the protected core area
were at risk of being casually shot, they were not purposely hunted or trapped
for sport or the fur trade. Thus, for comparative purposes, the population can
be considered as unexploited. In addition, the core area was dominated by
relatively xeric vegetative associations that differ considerably from habitats in
northern Florida and elsewhere in the eastern United States in which bobcats
previously have been studied. A feline panleucopenia virus (FPLV) outbreak
during the course of the study also provided an unexpected opportunity to
observe the effects of disease on the ecology and social organization of a wild
carnivore population.
The study area of approximately 200 km2 was located in Highlands County.
The protected core area was the 16 km2 Archbold Biological Station, 10 km
south of the town of Lake Placid (27011'N, 8121'W). The main period of the
study extended from January 1979 through March 1982, with incidental
observations made on marked animals through 1984.
ACKNOWLEDGMENTS
We thank Fred Lohrer for bibliographic assistance, Chester E. Winegarner for help in
handling and examining bobcats, Owen Minnick and Bert G. Crawford for aid in maintenance of
the tracking vehicle and telemetry equipment, Lilian Saul for assistance in data analysis, Dorothy
Carter for typing the manuscript, and J. F. Eisenberg and J. L. Wolfe for helpful comments on an
earlier draft of the manuscript. We were fortunate to have the opportunity to work with Hope
Ryden for several weeks in an intensive investigation of mother-kitten behavior on the study area
and profited greatly from her ideas and observations. We also are grateful to veterinarians J. H.
Causey, Citrus Animal Clinic, Lake Placid, Florida, and J. Carroll, J.C. Schwartz, and E. D.
Stoddard, Kissimmee Diagnostic Laboratory, Florida Department of Agriculture and Consumer
Services, for aid in diagnosing the cause of death of bobcats. Support for this study was provided
by Archbold Expeditions, Inc.; Defenders of Wildlife, Inc.; The Roosevelt Memorial Fund of the
American Museum of Natural History; and Sigma Xi, the Scientific Research Society.
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
STUDY AREA
The study area (Fig. 1) is located near the southern end of the Lake Wales
Ridge, a southward extension of the state's Central Highlands region and the
most prominent topographic feature of peninsular Florida. The Ridge is
characterized by relict sand dunes, scarps, and other features indicative of
former higher sea levels (White 1970). In the vicinity of the study area the
Ridge ranges from about 6 to 12 km in width and from 30 to 68 m in elevation.
The climate of the region is characterized by hot, wet summers and cooler,
drier winters. Mean annual rainfall and temperature are 1370 mm and 22.20C,
respectively. Relative humidity usually ranges from about 75-85% at dawn to
about 20-45% at midday throughout the year (Douglass and Layne 1978).
During the study, mean annual temperature was 21.90C, and the extreme high
and low temperatures were 37.2C and -7.20C, respectively. Daily maximum
and minimum temperatures for the warmer months (May-October) averaged
33.20C and 25.90C, respectively, while corresponding averages for the cooler
months (November-April) were 19.0C and 9.90C. Mean annual rainfall was
1201 mm, with 73% occurring from May through October. Standing water was
present in drainage canals, creeks, and seasonal ponds throughout 1979 and
early 1980. During summer 1980, most of these sources dried up and open
water was limited to two large and three small permanent lakes or ponds,
scattered livestock watering troughs, and an irrigation ditch system. Dry
conditions prevailed during the rest of the study despite normal rainfall in
1981.
Seven major natural vegetation associations (southern ridge sandhill, sand
pine scrub, scrubby flatwoods, flatwoods, swale, bayhead, seasonal ponds) are
found in the protected core area (Abrahamson et al. 1984). Similar
associations and various man-modified habitats occur on the remainder of the
study site. For purposes of this investigation, the following eight general
habitat types were recognized (percentage of each type in parentheses): closed
canopy xeric pine-oak (4), open canopy xeric pine-oak (28), flatwoods (21),
bayhead (7), citrus grove and tree nursery (16), oldfield (10), improved pasture
(12), and man-occupied (2). Figure 2 shows the distribution of these habitat
types in the study area.
The xeric pine-oak category includes the vegetative associations recognized
by Abrahamson et al. (1984) as southern ridge sandhill, sand pine scrub, and
scrubby flatwoods. These associations are characteristic of the deep sandy,
well-drained soils of the Lake Wales Ridge. South Florida slash pine (Pinus
elliottii var. densa) and sand pine (P. clausa) are the dominant overstory
species. Common understory and shrub layer species include turkey oak
(Quercus laevis), inopina oak (Q. inopina), Chapman's oak (Q.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
0 1 2
km
-
I
I
I
Figure 1. Study area showing Archbold Biological Station core area (stippled). Paved roads
indicated by solid lines, graded roads by dashed lines.
LAKE
GRASSY
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
,,,,', k Lake Placid 1 V
* 4444"4V.- 44
*. *. *. s.' .
Habitat Key
** XO
:t: XC
:V FW
SBH
CN
IP
OF
0 1 2
I 1
Figure 2. Habitats of the study area. XO = xeric pine-oak, open canopy;, XC = xericc
pine-oak, closed canopy; FW = flatwoods; BH = bayhead; CN = citrus grove and tree nursery;
IP = improved pasture; OF = old field; MO = man-occupied; paved roads indicated by solid
lines; railroad indicated by short dashed line; boundary of core area indicated by long dashed
line.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
chapmanii), sand live oak (Q. geminata), myrtle oak (Q. myrtifolia), scrub
hickory (Carya floridana), rusty lyonia (Lyonia fermginea), scrub palmetto
?(Sabal etonia), saw palmetto (Serenoa repens) and rosemary (Ceratiola
ericoides). Ground cover is generally sparse, consisting of grasses, forbs,
lichens, and shrub and tree sprouts. Xeric pine-oak habitats with canopy
coverage less than 50% were classed as "open canopy" and those with canopy
coverage greater than 50% as "closed canopy." The majority of open canopy
areas had less than 25% canopy coverage. The most extensive blocks of closed
canopy habitat were in a portion of the core area that had not been burned for
over 50 years.
Flatwoods occur on generally level, sandy soils with a relatively high water
table. South Florida slash pine is the dominant overstory species. Typical
shrub and ground cover components are gallberry (Ilex glabra), fetterbush
(Lyonia lucida), wiregrass (Aristida stricta), cutthroat grass (Panicum
abscissum), and saw palmetto. Grassy seasonal ponds and swales are included
in this category. Most flatwoods in the study area are relatively open, with
widely-spaced pines. However, small patches of flatwoods with dense pines
and heavy saw palmetto undergrowth often occur at the edges of ponds, lakes,
and bayheads and in parts of the core area where fire has been long excluded.
Bayheads, characterized by broad-leaved evergreen trees that form a dense,
closed canopy, occur along creeks, at lake edges, and in shallow depressions
with muck soils in flatwoods. The typical overstory species include loblolly bay
(Gordonia lasianthus), red bay (Persea borbonia), sweet bay (Magnolia
virginiana) and slash pine. Characteristic shrub layer components are young
bay trees, wax myrtle (Myrica cerifera), gallberry, and saw palmetto. Mosses
and ferns are often abundant components of the ground cover, and muscadine
grape (Vitis rotundifolia) is common along edges.
Citrus groves and tree nurseries are found principally on land that formerly
supported xeric pine-oak communities. As the groves are periodically disced,
ground cover between rows is generally sparse or absent. However, grasses
and forbs may become extensive in groves that have not been disced for some
time. The oldfield category includes vacant lots, fallow agricultural fields,
decadent citrus groves with sparse dead trees and rank grass and weedy ground
cover, pastures overgrown with weeds and brush, and railroad and road
right-of-ways. Improved pastures are open areas of dense, short-cropped
natural or exotic grasses with widely scattered shrubs, clumps of palmettos, or
pines. A golf course in the study area also is included in this category.
Man-occupied areas consisted of three light industrial complexes of about 3 ha
each, an extensive housing development with scattered houses and much open
land, a mobile home park, a recreational vehicle park, several areas containing
clumped rural residences, and a few gardens or agricultural fields. The study
area was traversed by a railroad and two major highways and contained a
166
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
number of secondary paved and unpaved roads. The core area contained a
network of 4-wheel drive roads, foot trails, and firelanes.
METHODS
Capture and Handling
Bobcats were captured with National live traps (104 x 50 x 40 cm). From 1 to 10 traps were
deployed at any given time. Trapping was concentrated in the core area in an attempt to capture
all bobcats utilizing that area. Of a total of 109 trap sites, 107 were distributed throughout the
core area, 1 was located adjacent to the boundary of the core area, and another 0.5 km from the
core area. The number of trapnights (TN) per site ranged from 1 to 61, with a total of 2013 for
all sites. Baits included live animals (cotton rats, Sigmodon hispidus; adult domestic rabbits;
young and adult chickens) and pieces of meat (chicken; cottontail rabbit, Sylvilagus floridanus;
gray squirrel, Sciums carolinensis). Meat baits were suspended by a string just behind the trap
treadle and live animals were housed with food and water in separate wire-mesh enclosures
attached either inside the trap above and behind the treadle (cotton rats) or to the back of the
trap (rabbits, chickens).
Captured bobcats were sedated with intramuscular injection of ketamine hydrochloride
("Ketaset," Bristol Laboratories, Syracuse, New York) at doses ranging from 5 to 36 mg/kg of
body weight. Low doses were given when changing collars and higher doses when more thorough
examination was necessary. Data recorded for each animal included body measurements (total
length, tail length, hind foot, ear from notch, neck circumference) and weight; length and
diameter of the upper right canine; pelage condition and markings; ectoparasites; reproductive
condition; presence and nature of injuries or scars; and length and width of foot pads and notes
on their shape and symmetry. Weight; dental condition, including amount of wear, coloration,
and stage of replacement (Crowe 1975); and appearance of teats of females and the scrotum of
males were used to classify cats as adults or juveniles. Plaster casts of the right fore and hind feet
were made to aid in identifying individual bobcats by tracks in the field. The animals were
marked with an ear tag in one ear and an alphanumeric tattoo in the inside of the other ear.
Radio collars were color coded with reflective paint or with colored tape to facilitate visual
identification.
Subjects
Seventeen bobcats were radio-collared (Table 1), including 13 adults (6 males, 7 females) and
4 juveniles (2 males, 2 females). Two additional individuals handled during the study included an
emaciated 5.3 kg adult female (F2) with a severe infestation of mange mites (Notoedres cati) that
died after being darted and a 2.4 kg juvenile female (F7) captured twice and released without
radio-tagging due to her small size. Mean and extreme weights of adult males and females were
9.5 kg (8.1-10.5) and 7.9 kg (5.8-10.1), respectively. Weights of individuals classified as juveniles
ranged from 5.3 to 7.9 kg (X = 6.1).
One of the females (Fl) included in the study was a semi-tame individual. She was captured
outside the study area in spring 1974 and kept in a cottage on the Archbold Biological Station
from mid-September 1974 until May 1975 when about a year old, then released at the site
(Winegarner and Winegarner 1982). She reappeared at the cottage 16 days later and continued
to return periodically. She was often fed when visiting the cottage. No effort was made to tame
the cat during captivity, and she was not handled after release, except when captured and sedated
for a series of treatments for mange in 1978 and for attachment of a radio-collar in the present
study. She was tolerant of, but not friendly to, humans; and, except for her visits to the cottage,
Table 1. Weights and measurements of radio-collared bobcats.
Body Measurements (mm) Upper Canine (mm)
Date of Ear Maximum Length
Original Weight Total Hind from Diameter from Gum
Individual Capture (kg) Length Tail Foot Notch at Gum Line Line to Tip
ADULT MALES
M1 28 Apr 79 9.4 895 139 163 85 8.7 16.9
M2 5 May 79 9.5 931 167 168 71 9.2 15.6
M3 9 Aug 79 9.0 908 155 173 70 7.5 15.8
M6 19 Apr 80 9.1 978 160 183 67 7.0 16.5
M7 26 Apr 80 9.5 986 181 191 65 6.8 16.2
M8 11 Sep 80 10.5 901 148 173 71 7.1 16.9
ADULT FEMALES
F1 8 Dec 79 8.8 913 182 170 63 6.1 13.4
F3 1 Jun 79 5.8 845 160 160 62 6.1 11.9
F4 25 Jul 79 7.8 845 138 163 61 8.4 12.7
F8 31 Jan 80 6.5 837 158 160 71 5.6 13.3
F9 1 Feb 80 7.8 865 150 154 70 5.6 15.0
F10 13 Feb 80 9.9 894 146 163 65 6.4 13.9
F11 9 Mar 80 9.4 910 168 172 65 6.6 14.2
JUVENILE MALES
M4 11 Oct 79 5.3 770 155 160 71 6.7 14.0
M5 11 Feb 80 7.9 954 174 188 61 7.2 16.0
JUVENILE FEMALES
F5 27 Nov 79 5.7 795 170 170 70 5.6 12.5
F6 7 Dec 79 5.4 806 156 159 65 6.5 12.9
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
her behavior appeared not to differ significantly from that of wild bobcats. Various aspects of
the behavior of this individual were reported by Winegarner (1985a).
Study Techniques
The principal study method was radiotelemetry, but additional data were obtained from
tracking, sightings, and observations of sign. The mean number of records (including trap
captures, radio fixes, and sightings) for individual bobcats was 320, with a range of 7 to 1248. The
mean interval between the first and last records of marked cats was 327 days, with a range of 9 to
1143 days.
Most of the radiotracking was done from a 4-wheel drive vehicle equipped with a marine
compass mounted on the dash and an 8-element, dual-Yagi null peak antenna system mounted
through the roof so that it could be rotated from within. A hand-held, collapsible, 4-element Yagi
antenna also occasionally was used to approach a stationary bobcat during the day in a rest site
away from a road. Radio collars, manufactured by AVM Instrument Company or Davidson
Electronics, weighed 127-185 g, had a pulse rate of 60-121 beats/minute, and transmitted in the
150-151 mHz range. Collar antennas were either external whip-type or copper alloy bands
incorporated into the collar material. Most of the positions of radio-collared bobcats were
determined by triangulation at distances less than 1 km. Guenther (1980) found that at a
distance of 1 km triangulation was accurate to within an area of about 4 ha. Data recorded for
each radio fix included date, time, weather, and activity state (moving or inactive) based on the
nature of the signal.
Intensive radiotracking was conducted from April 1979 through December 1981. A total of
5344 radio locations was obtained on the 17 instrumented bobcats over the 32-month period.
Tracking was conducted at all hours of the day and night. Emphasis was placed on monitoring
significant events such as male-female interactions or movements of a female with newborn young
rather than on locating each individual at some fixed time schedule. Individuals were monitored
for periods ranging from 15 minutes to 24 hours for 1 to 35 consecutive days separated by
intervals of usually less than a week. Following the termination of major field work at the end of
December 1981, we continued to monitor on a less regular basis the movements of several
individuals by radiotracking until March 1981, and by sightings and tracks until December 1984.
Trailing bobcats on foot provided additional information on movements and activities of
particular individuals; marking behavior; litter size; adult male-adult female and female-young
interactions; and the presence, sex, and age of unmarked cats. The probable presence of
unmarked bobcats on the study area was assumed from the occurrence of tracks that did not
match those of known individuals. If tracks believed to be of the same unmarked individual were
repeatedly found on the study area, that individual was considered a resident. When such tracks
consistently occurred at the periphery of an instrumented bobcat's home range, the unknown cat
was assumed to be of the same sex as the marked individual. If the unknown tracks were within
the interior of the range of a collared cat, the unknown individual was assumed to be of the
opposite sex. This interpretation is based on the findings of Lawhead (1978), Miller (1980) and
other investigators that same-sexed bobcats exhibit very little range overlap while opposite-sexed
individuals may exhibit substantial overlap. On the basis of this assumption portions of the range
boundaries of several bobcats were determined prior to their capture. Lembeck (1978) also used
this method to identify the sex and to estimate the range of an unmarked bobcat on his study
area and later confirmed the sex and range estimate by capturing and radiotracking the
individual.
Three types of marking behavior recognized in this study included:
1) Scrapes: Distinctive elongate ruts or ploughedd" areas in the soil or
litter made by alternating rearward thrusts of the hind feet with the
body in a semi-squatting position and usually containing either feces or
urine.
2) Urine marking: Deposition of urine onto the substrate or objects on
the ground from a squatting position (squat-urination) or spraying it on
above-ground objects from an upright posture (spray-urination).
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
3) Scat marking: Deposition of scats which are left exposed.
Exposed scat deposition sites were counted along a 10-km route of primitive roads, firelanes,
and footpaths through various habitats in the core study area during February, March, July, and
August 1979 (Guenther 1980), and more intensive censuses of scrapes and scats were conducted
from October 1979 through April 1981 (Wassmer 1982). Foot trails and railroad tracks were
walked and primitive roads or firelanes were surveyed from a vehicle at a speed of 1-5 km/hr. All
scats were collected, and scrapes were usually marked with a toothpick to prevent their being
recounted in a subsequent census. In the October 1979-April 1981 period, regular censuses were
made along 37 km of routes, which included the 10-km route used by Guenther (1980). Most
routes were censused once or twice a month; a few regularly-driven roads were inspected more
frequently; and some trails that were infrequently marked were searched every 1 to 3 months.
Other parts of the study area were searched irregularly. As it was not possible to census all
routes on the first day of each month, several types of evidence were used to estimate the age of a
mark so that it could be assigned to a particular month. These included time since the route was
last searched, whether or not the mark was made before or after a recent rain, amount of vehicle
tracks or other disturbance in the vicinity of the site, and the condition of the scat or scrape.
Totals of 2220 exposed scats and 5291 scrapes (including scrapes containing scats) were recorded.
Of these, 1461 (66%) scats and 3326 (63%) scrapes were located along the regular census routes.
A total of 349 sightings of bobcats were made by us or reported by others during the study.
Sixteen of the collared cats and 10 unmarked but recognizable (e.g. kittens accompanying a
collared female) individuals were observed. In addition, unidentified bobcats were seen on 30
occasions.
Information on food habits was obtained from analysis of 146 scats; 69 were collected in the
core study area on a random basis from 1967 to 1978, and 77 were collected from January to
September 1979. Each scat was soaked in detergent for 3 or 4 days, then rinsed in a sieve with
fine wire mesh until all fine debris was removed and the remaining material oven dried for
examination. The minimum number of individuals of a given prey species represented in a scat
was based on the number of the most frequent element occurring singly in a skeleton (e.g., left
third upper molar). Weights of mammals and other vertebrate species used to convert prey
frequency of occurrence to biomass values were obtained from specimens collected in or near the
study area.
Data Analysis
Density estimates were based on the cluster of individuals centered on the core area that was
most intensively and continuously monitored. Estimates were computed for 12 unequal time
intervals during the period from April 1979 through August 1981 for which the most complete
data on the number and sexes of individuals and sizes of home ranges were available. Five of the
intervals were delimited by known deaths or disappearance of individuals. Break-points for the
remaining intervals were more subjective, involving times of collar failures which prevented
further detailed monitoring of individuals or prolonged (about 1 month) gaps in radiotracking.
For each period, the area used for calculating density was that of the minimum convex polygon
formed by the outermost boundaries of the cluster of contiguous or overlapping home ranges of
the individuals present during that interval. Individuals known or assumed to be present on the
study area during a given interval on the basis of tracks or other evidence, but for which there
was no, or insufficient, data on home range, were treated in 1 of 2 ways. If they were located on
the periphery of the cluster of known home ranges, they were excluded from the calculations. If
they were within the cluster and data on their home range from a prior or subsequent time
period indicated that the range was most likely included within the cluster during the current
period, they were included in the density estimate. Estimates of juvenile density were based on
the total number of juveniles known or believed to be present within female ranges. As number
of young in a litter usually could not be determined until the young were approximately 2 months
or older and moving with the mother, juvenile density estimates apply to mobile young prior to
dispersal.
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
The validity of this method of density estimation rests on the assumptions that (1) male
home ranges do not overlap appreciably, (2) male home ranges are essentially contiguous, with
little or no unoccupied areas between them, and (3) female ranges are included within male
ranges. Although these assumptions were probably not fully met, the available data suggest they
generally applied on the core area. Any bias in the method is probably in the direction of an
overestimate of density, particularly for the entire study area. On the other hand, using the
alternative method of dividing the total study area (as determined by maximum movements of
individuals captured and marked on the core area) by the number of bobcats believed to be
present would probably significantly underestimate density because of the increasing probability
of not detecting the presence of bobcats at increasing distances from the core area.
Locations of marked individuals obtained by radiotracking, capture, or visual observations
were plotted on a large scale (1:4800) map of the study area gridded at 200 m intervals into 4-ha
quadrats. The 4-ha quadrat size was selected as the minimum area of resolution based on the
accuracy of radio fixes at distances of 1 km or less. Home range areas were estimated by the
minimum convex polygon method (Mohr 1947). For purposes of this study, the area used by an
individual based on all locations over the entire period it was monitored is termed the "overall"
home range, and areas used by individuals during one of the 12 time periods mentioned above
are designated as "short-term" home ranges. The distribution of fixes among the 4-ha quadrats
enclosed by home range boundaries was used as a measure of the intensity of utilization of home
range areas (Siniff and Tester 1965).
Estimates of daily movements were based on straight-line distances between the first radio
locations on consecutive days of monitoring.
Whether a bobcat was moving ("active") or stationary ("inactive") was determined by the
nature of the signal and the animal's location on successive fixes. When more than one fix was
available for a bobcat in a given hour, the first record was arbitrarily selected to indicate the
animal's activity state during that hour. The period between 2400 and 0600 hours was relatively
poorly sampled, with only 325 (7%) of the total of 4966 hourly records included within this
interval.
The amounts of different habitats contained within home ranges of individual bobcats were
determined by counting the number of 4-ha quadrats containing each type. When more than one
habitat occurred within a quadrat, each was assigned a fractional value corresponding to the
number of habitat types represented, regardless of the actual coverage of the habitats in the
quadrat. Habitat preferences were assessed by comparing the observed frequencies of locations
in quadrats representing different habitats with expected frequencies based on the relative areas
of those habitats within the home range. Fixes within quadrats containing more than one habitat
were arbitrarily assigned fractional values for use of each habitat corresponding to the number of
habitats represented within the quadrat.
Statistical tests used include Mann-Whitney U (U), Spearman rank correlation (Rho), and
Chi-square (X ) as described in Siegel (1956) and the Log-likelihood ratio (G) given in Zar
(1984).
RESULTS AND DISCUSSION
Capture Success
Overall capture success (18 original captures, 19 recaptures) was 1.8
captures/100 TN. The number of TN in different seasons ranged from 609 to
660, and capture success (per 100 TN) was as follows: December through
February, 3.1; March through May, 1.1; June through August, 0.7; September
through November, 1.1.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
Meat baits were more effective than live baits or live and meat baits
combined. All captures with live baits were in traps baited with chickens.
Capture rates per 100 TN were meat baits 2.5, live baits 1.1, and mixed baits
0.4. The difference in capture frequencies between live and meat baits was
significant (X2 = 6.59, 1 df, p < 0.05). Bobcats also tended to be captured
sooner with meat baits than with live baits (X = 1.8 days vs. 7.9 days).
The overall capture rate in this study was relatively high compared with
that (0.26/100 TN) reported from northeastern Florida by Progulske (1982)
and elsewhere in the southeast. Trapping success with steel traps, live traps,
and mixed steel and live traps in studies in Alabama, Louisiana, South
Carolina, and Tennessee ranged from 0.10 to 4.8/100 TN, with a mean of
1.5/100 TN (Hall 1973, Kight 1962, Kitchings and Story 1979, Lueth 1962,
Miller 1980). Trap success rates in the southeast are generally comparable to
those in other parts of the bobcat's range. Capture rates with steel traps at two
sites in Arizona were 0.72 and 1.33/100 TN (Jones 1977, Lawhead 1978); and
Lembeck (1978) and Gould (1980) reported rates of 1.02 and 1.04/100 TN with
mixed steel and box traps in two areas in California.
Critical comparison of trapping efficiency in different studies is difficult
because of the great variety of types of bait, traps, and techniques used by
different workers. One of the factors that may potentially influence capture
success in mark-and-release studies is a change in susceptibility to capture of a
given individual as a result of previous experience with traps. In the present
study, trap success generally was high when new, unmarked bobcats were
targeted for capture. In contrast, previously captured bobcats often appeared
to avoid traps. Tracks showed that marked individuals walked past open traps
on numerous occasions. Behavior of females (especially those previously
trapped) with young may reduce chances of capturing the young. For example,
despite intensive efforts the two kittens of an adult female in 1980 could not be
trapped, although her three offspring the previous year were captured two or
more times each using similar traps, baits, techniques, and approximately the
same level of effort. However, in 1980 the mother urinated on traps or made
fecal or urine scrapes in front of them on a number of occasions, most
frequently after she had been captured. This behavior, which may have served
to inhibit the kittens from entering, was not observed the previous year.
Berrie (1973) reported what seems to be similar behavior of an adult male lynx
(Felis lylnx) which deposited very small amounts of feces (= "tokens," Schaller
1967) in front of 6 traps on 1 night without being captured.
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
Demographic Characteristics
Density.- Estimated overall mean density of bobcats for the period April
1979 to August 1981 was 26 individuals/100 km2. Mean densities of adult
males, adult females, and juveniles during this period were 5, 8, and 13/100
km2, respectively. Overall densities in different periods of the study ranged
from a maximum of 42/100 km2 in the 1 July-25 October 1979 interval to a low
of 14 in the 29 February-30 April 1980 interval (Table 2). Numbers of adult
males ranged from a high of 7/100 km2 in summer-fall 1979 to 0 in late winter
1980. Maximum and minimum densities of adult females were 12/100 km2 in
spring-early summer 1979 and 6 in fall 1980. Male density estimates for the
different time periods ranked significantly lower (U1212 = 7.5, p < 0.01,
2-tailed) than those of females, with males showing a more pronounced decline
in late fall and winter 1979-80. Male density was still below the original level at
the end of the study. Highest (26/100 km2) juvenile density was attained in
summer-fall 1979; no mobile juveniles with resident females were recorded on
the study area during the 29 February-30 April 1980 interval. Numbers of
juveniles were relatively high in 1979, declined through 1980, and increased
again in 1981.
The overall mean density of bobcats in this study was half of that (52/100
km2) estimated by radioisotope marking in northeastern Florida by Conner
(1982). Density estimates based on radiotracking elsewhere in the southeast
include 77-116/100 km2 in Alabama (Miller and Speake 1978), 13-19/100 km2
(Kight 1962), and 58/100 km2 (Provost et al. 1973) on the Savannah River
Plant in South Carolina, and 9-18/100 km2 in Virginia (Progulske 1952).
Densities of bobcats in the southeastern United States tend to be higher than
values reported for northern populations and are broadly comparable to those
from the western United States (McCord and Cardoza 1982). However,
detailed comparisons between most published population data are not possible
because of the variety of techniques and assumptions involved in density
estimates by different workers.
Sex and Age Ratios.- The overall mean age ratio based on the bobcats
known or assumed to be present during the 12 time intervals was 1.00
juvenile/adult (Table 2) compared with a 0.42 juvenile/adult capture ratio.
The difference reflects the difficulty of trapping juveniles still in the company
of their mother. Juvenile/adult ratios closely tracked the population trend,
being high from July 1979 to early February 1980, low during most of 1980, and
increasing from March to August 1981. Adult sex ratios over the 12 time
intervals ranged from 0 to 1 male/female (X = 0.64 male/female, Table 2).
The proportion of adult males to females declined sharply from late October
1979 to early February 1980 then increased to a fairly stable level by the
Table 2. Estimated numbers of individuals, densities (individuals/100km ), adult sex ratios (males/female) and age ratios (juveniles/adult) of
bobcats on the study area during 12 time periods (see text for methods).
1979 1980 1981
28 Apr 1 Jul 26 Oct 17 Jan 6 Feb 29 Feb 1 May 20 Jul 8 Oct 1 Dec 9 Mar 1 Jul
to to to to to to to to to to to to
30 Jun 25 Oct 16 Jan 5 Feb 28 Feb 30 Apr 19 Jul 7 Oct 30 Nov 8 Mar 30 Jun 12 Aug
NUMBER
Ad. males 3 3 2 1 0 3 4 4 4 4 4 3
Ad. females 5 4 4 4 5 5 5 5 5 5 4 4
Juveniles 2 11 11 9 6 0 7 7 7 7 9 9
Total 10 18 17 14 11 8 16 16 16 16 17 16
DENSITY
Ad. males 7 7 5 3 0 5 6 6 5 5 6 4
Ad. females 12 9 9 10 10 9 8 7 6 7 7 7
Total adults 19 16 14 13 10 14 14 13 11 12 13 11
Juveniles 5 26 26 24 12 0 11 10 8 9 15 15
Overall 24 42 40 37 22 14 25 23 19 21 28 26
SEX RATIO 0.60 0.75 0.50 0.25 0 0.60 0.80 0.80 0.80 0.80 1.00 0.80
AGE RATIO 0.25 1.38 1.83 1.80 1.20 0 0.78 0.78 0.78 0.78 1.13 1.29
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
following summer. A similar trend in sex ratio during a "crash" and recovery of
a California bobcat population was observed by Lembeck (1986). Thirteen
juveniles whose sex was known included 7 males and 6 females (1.17
males/female). Adult and juvenile sex ratios of the bobcats trapped were 0.86
and 1.00 male/female, respectively.
Breeding Season.- Eight litters whose birth dates could be determined to
within a week were born in April (4), May (2), October (1), and January (1).
Births of four other litters of radio-collared cats were estimated to have
occurred in February (1), April (1), and May (2); and an unmarked female on
the periphery of the study area apparently produced a litter in April. Based on
a gestation period of about two months (McCord and Cardoza 1982), the
breeding season extended from August through March, with 10 of the 13
known or estimated mating dates occurring in February and March and 1 each
in August, November, and December.
Variously derived estimates of the breeding season in other parts of the
range include February to April in 11 western states (Duke 1954); January to
July or later in Utah (Gashwiler et al. 1961); January to July or later in
Wyoming (Crowe 1975); December to March in Arkansas (Fritts and
Sealander 1978); February to July with peaks in March and April in Alabama
(Miller 1980); February to mid-March in South Carolina (Griffith and Fendley
1986); and November to July in Texas (Blankenship and Swank 1979).
Comparison with these data suggests that there may be more fall and early
winter breeding in southern Florida than elsewhere in the range.
Natality.- Mean litter size of 1 unmarked and 12 radio-collared females
was 2.6 (range = 1-5). As all litters observed were over 2 months of age and
may have experienced some mortality, mean litter size at birth was probably
higher. Four litters of the semi-tame female (Fl) during the study averaged 3.5
with a range of 2-5 compared with a mean of 2.2 and range of 1-3 for 9 litters
of other females. This suggests higher litter size at birth for F1 or better
survival of her young, possibly as a result of the supplemental feeding she and
her kittens received at the cottage they visited. Mean litter size in this study
was lower, particularly if litters of the semi-tame individual are omitted from
the sample, than values (2.8-3.5) based on observations of kittens in three
studies in the western United States (Bailey 1972, Gashwiler et al. 1961,
Zezulak and Schwab 1979).
Two females (F8, F9) gave birth to litters when about 1 year old. The low
number of young (1 and 2) in these litters suggest that young primiparous
females produce smaller litters than older females. The first litter of the
semi-tame female (Fl) was also smaller than the average of succeeding litters
(Winegarner and Winegarner 1982). Breeding between the first and second
years of life has been recorded in other bobcat populations (e.g. Crowe 1975;
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
Brittell et al. 1979; Fritts and Sealander 1978; Johnson and Holloran 1985), but
available data are insufficient to provide an adequate basis for interpopulation
comparisons in frequency of early breeding in females.
The semi-tame female (Fl) had 4 litters (April 1979, May 1980, April 1981,
October 1981) over a 31-month period. She also produced a litter during each
year from 1976 to 1978 (Winegarner and Winegarner 1982). Thus, she
typically bore only one litter per year, although two were produced in 1981.
The second 1981 litter was not the result of recycling following the loss of a
recently-born litter, as young of the first litter were seen with her until
September, and there was circumstantial evidence that at least 1 of them
remained in her range until December. Although the female was occasionally
artificially provisioned and thus may have been in a better nutritional state than
the typical wild female, this case suggests that bobcats in the southern part of
the range occasionally may be capable of producing two litters in a year,
although one is the norm. Estimated birth intervals for two other females (F8,
F9) that produced two litters while being monitored were 8 months in both
cases (April-January and May-estimated February).
Mortality and Injuries.- Of the 17 instrumented bobcats, 9 were known to
have died between April 1979 and August 1982, including 5 of 6 adult males, 2
of 7 adult females, and 2 of 4 juveniles. The other juveniles of a litter of three
disappeared at the same time one died, suggesting that all three perished.
Including these two individuals, the mortality rate during the 40-month period
was 54% for adults, 80% for juveniles, and 56% for all marked cats. In
addition, nine unmarked bobcats (4 adult males, 2 adult females, one juvenile
male, one juvenile female, and one unsexed juvenile) died or were found in a
moribund condition in or adjacent to the study area between January 1979 and
August 1982.
Including both known and probable deaths and causes, 8 of the 17
instrumented bobcats were killed by feline panleucopenia infections and 3 by
vehicles. Of the 9 unmarked individuals, 5 (2 adult males, 1 adult female, 1
juvenile male, 1 juvenile female) were killed on roads, 2 adult males were shot,
1 unmarked juvenile (sex unknown) was killed by dogs, and 1 adult female with
a severe case of Notoedric mange died within a few minutes of capture. The
last individual was weak and extremely emaciated (5.3 kg vs. mean adult female
weight of 7.9 kg) and undoubtedly would have soon died if she had not been
captured. She had been periodically observed in the study area over a 5-week
period before capture, during which time she became progressively thinner and
weaker. Three females (F4, F10, Fll) among the animals live-trapped and
radio-collared from July 1979 to March 1980 also had scabby areas with sparse
hair or bare patches on the head, neck, or shoulders, suggesting a current or
former mild mange infestation. The partially decomposed carcass of an adult
male (M2) found in November 1979 also had similar bare patches on the inside
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 177
of the forelegs. In 1978, prior to this study, the semi-tame female (Fl)
developed a severe case of mange and probably would have died if she had not
been captured and treated; and her four kittens that year also apparently died
from mange (C. E. Winegarner, pers. comm.). These data suggest that there
was a relatively high incidence of mange in the bobcat population of the study
area during 1978 and 1979.
Direct and circumstantial evidence indicated that a feline panleucopenia
epizootic occurred among the bobcats of the study area during the fall and
winter of 1979-1980. The deaths of 4 marked individuals (adult males M1, M3;
adult female F10; juvenile male M5) whose fresh carcasses were recovered in
January and February 1980 were diagnosed as being due to the disease.
Circumstantial evidence also suggested that four other individuals, including an
adult male (M2) and a marked juvenile female (F6) and her two siblings (M4,
F5), also died from the disease. In addition two adult females (Fl, F4) were
suspected to have had sublethal infections based on their behavior (see below).
Whether only necropsied animals or all possible cases are included, mortality
from FPLV from October 1979 through February 1980 accounted for a
significant proportion of the known bobcat population, including 3 or 4 of 8
adults and from 1 to 4 of 11 juveniles. Sexes of bobcats known or suspected to
have died from FPLV included 2 or 3 of 3 males and 1 of 5 females among
adults and 1 or 2 of 3 males and 0-2 of 3 females among known-sex juveniles.
Data on the symptoms of the disease and its effect on behavior were
obtained for several of the instrumented bobcats. All known or suspected
FPLV victims exhibited a progressive reduction in movements from 2 to 4 days
prior to death. A juvenile male was glassy-eyed and lethargic when recaptured
4 days prior to his death and was slow to move away from the observer when
released. Disturbance of the ground around the body, which was found soon
after death, indicated that the animal had struggled. A large amount of
greenish, apparently bile-tinted, fluid exuded from the mouth while the carcass
was being transported to the laboratory. An adult male observed near a pond
shortly before death was unable to get on his feet or hold his uncontrollably
bobbing head erect. Greenish fluid was dripping from his mouth. When
checked 2 hours later, he was dead, perhaps drowned, in the pond in water
about 10 cm deep. The surrounding vegetation was matted down, indicating
the animal had struggled before dying. Four other bobcats known or believed
to have died from FPLV also were found near water.
Circumstantial evidence suggests that adult female F4 was principally
responsible for the spread of the disease through the population. The first
death attributable to FPLV was that of an adult male (M2) in late October
1979. M2 and F4 had overlapping home ranges and probably were in
occasional contact outside the breeding season. Therefore, F4 may have
transmitted the disease to M2 or received it from him. On 14 January 1980
from 2000 to 2100, F4 and adult male M3 were in close proximity based on
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
radio fixes. Tracks at the site the next morning also indicated they had been
together. M3 was found dead on 16 January and had a FPLV infection based
on laboratory diagnosis. Radio locations indicated that F4 and adult male M1
had associated together between midnight 31 January and 0200 on 1 February.
The following night M1 was in the vicinity of, if not in actual contact with, F6,
one of three juveniles of Fl, whose home range was contained within his. As
these young were still closely associated, the other two juveniles (M4, F5)
probably were also in the area, but their radio-collars were not functioning.
Both Ml and F6 apparently died on or about 5 February. F6's carcass,
recovered in the area where she and M1 had been located 4 days before, was
too decomposed for necropsy. No sightings or tracks believed to be of her
litter mates were recorded after this date, suggesting that they also died from
the disease.
During the period of apparent contact between M1 and one or more of Fl's
young, F1 was in another part of her range and did not return to the site until
after the male had left the area. Over the next two weeks, she spent an
unusual amount of time in that area and in another remote portion of her
range with canals and a pond containing water. C. E. Winegarner (pers.
comm.) also reported that she stayed away from the cottage where she was
occasionally fed for 18 days from late-January to mid-February, her longest
period of absence on record. Her apparent attraction to water and prolonged
absence from the cottage area suggest that she may have had a sublethal FPLV
infection (Bittle 1970), which she could have acquired either from M1 or her
young. F4 may also have had a sublethal infection during the winter-early
spring period. This could have contributed to her effectiveness in transmitting
the disease to other bobcats, as Bittle (1970) stated that an animal recovering
from an infection could remain a carrier for a long period. F4's behavior
during this period was abnormal. Following the death of M2, her movements
became more restricted, and she was observed on three occasions (once near
water for about an hour) in February and March 1980 walking slowly or lying
down in the open and could be easily approached to within a few meters.
The two remaining bobcats (juvenile male M5, adult female F10) believed
to have died of FPLV in late February occupied home ranges adjacent to F4's
and thus could have been infected by her. M5 and F4 were recorded visiting
the same sites along their common range boundaries during this period.
Only 1 of the 17 bobcats live-trapped in this study showed signs of current
or past injury. This was the semi-tame female (Fl). A small cloudy area in the
lower portion of the left cornea with a tiny wound in the center was noted
during laboratory examination of the animal in October 1980. On occasions
when she was observed at close range in the field during the previous 2 weeks,
the eye was watering profusely and was kept closed almost continuously. The
eye appeared normal when she was seen 2 weeks later (C. E. Winegarner, pers.
comm.). In October 1982 she was observed limping badly, a forefoot dangling
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
helplessly. She was nursing a litter of two kittens at the time. She also
appeared to recover fully from this injury.
Of the known and probable causes of deaths of radio-collared bobcats in
this study, a substantially higher proportion of mortality was due to natural
than to man-related causes (73% vs. 27%). In generally comparable studies of
radio-collared bobcats in exploited or unexploited populations in other parts of
the range (Alabama, California, Idaho, Minnesota, Oklahoma), natural causes
accounted for an average of about 38% of deaths, with a range from 0 to 100%
(Bailey 1972, Fuller et al. 1985, Gould 1980, Lembeck 1978, 1986, Miller 1980,
Rolley 1985). The present study, in which over half (4 of 7) of the resident
adults were killed by feline panleucopenia in a 4-month period, demonstrates
that the proportion of deaths due to natural causes as well as the actual rate of
natural mortality can be high. Thus, Crowe's (1975) model of the annual cycle
of bobcat numbers which assumes adult mortality from factors other than
trapping to be negligible is clearly not applicable to all populations. It is
difficult to assess the relative importance of various mortality factors for other
than radio-collared bobcats because of a serious sampling bias; there is a
greater probability of recovering animals that have died from man-related
causes, such as shooting or being killed on roads, than animals that have died
from natural mortality agents. In the present study, for example, it is highly
unlikely that the carcasses of any of the bobcats known or suspected to have
died from FPLV would have been recovered if they had not been
radio-collared.
McCord and Cardoza (1982) noted that documentation of diseases in wild
populations of bobcats was sparse and stated that "...bobcat populations have
not succumbed to epizootics or die-offs due to heavy parasitic infections...,"
citing the commonly reported solitary nature and habits of the species as an
explanation for the apparent lack of infectious diseases in bobcats. In contrast,
our findings suggest that parasites and disease can be important mortality
agents in bobcat populations. The relatively high incidence (24%) of current
or apparent former Notoedric mange infestations in bobcats that were
captured, including F1 who undoubtedly would have died from mange prior to
the study if she had not been treated; the capture of one individual (F2) near
death from a heavy mange infestation; and the probable death of Fl's 1978
litter of four young from mange suggests that heavy parasitic infections can be
a significant cause of bobcat mortality in Florida. Deaths of bobcats from
mange also have been reported in other geographic regions (Pence et al. 1982,
Penner and Parke 1954, Pollack 1949).
Our study also indicates that feline panleucopenia may be an important
mortality agent in Florida bobcat populations. Progulske (1982) also
documented an apparent die-off of bobcats in northeastern Florida during
summer 1980, which may have been due to a FPLV outbreak. Mortality from
FPLV also has been reported in bobcats in other widely-separated parts of the
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
range. Lembeck (1978, 1986) and Gould (1980) recorded confirmed deaths of
bobcats from FPLV in California. In an unharvested population studied by
Lembeck (1986) from 1976 to 1982, 11 of 22 deaths from known, non
study-related causes resulted from natural causes, and five of these were
attributable to panleucopenia. FPLV was the probable cause of death of two
of five radio-collared bobcats in a study on the Savannah River Plant, South
Carolina (Griffith and Fendley 1986). Fox (1983) concluded that feline
panleukopenia was probably an important cause of bobcat mortality in New
York based upon diagnosed cases of the disease in the Adirondack and Catskill
mountains and a relatively high (21%) prevalence of FPLV antibodies in a
statewide sample of bobcats.
Our data suggest that FPLV could have been transmitted indirectly through
contaminated feces or urine (Csiza et al. 1971), as well as by actual contact
between animals. Bobcat marking with exposed scats was most frequent
during winter, and bobcats were known to visit each other's marking sites.
Bouillant and Hanson (1965) found that healthy mink (Mustela vison) who
received stomach inoculations of 20% suspended feces passed by animals
experimentally infected with mink enteritis virus (MEV) developed clinical
symptoms of MEV, even when carrier feces were half-buried for several
months during cold, damp weather, which favored survival of the virus. The
winter of 1979-1980 in south-central Florida was relatively cool and wet. These
facts suggest that bobcats might become infected through investigating
contaminated feces and that weather conditions could influence the probability
of an outbreak by affecting survival of the virus. The higher incidence of FPLV
mortality in males than females suggested by our data may reflect the larger
home range size of males (see below), which might increase their probability of
contacting infected animals and/or feces. Further, FPLV infections occurred
during the peak period of marking, which might also have increased chances of
virus transmission.
In addition to being a cause of death of young or adult bobcats, FPLV may
also kill embryos or fetuses of pregnant females with a sublethal infection
(Povey and Davis 1977). It may be significant in this connection that female
Fl, believed to have had a sublethal infection during winter 1979-80, produced
only two young in her first litter following this period, whereas her two
previous litters and subsequent two litters numbered three, four, and five, four,
respectively. In addition, F4, also suspected of having a sublethal infection, was
the only collared female in the population who did not rear a litter in the year
following the epizootic.
Although FPLV was probably spread through the bobcat population by
contact with infected individuals or contaminated feces, other potential vectors,
including free-ranging domestic cats (Felis catus) and raccoons (Procyon lotor),
were present in the study area. Feline panleukopenia is common in domestic
cats throughout the United States, and Goss (1948) reported that raccoons are
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
susceptible to FPLV. Feral domestic cats were seen regularly in the study area
prior to the epizootic but not for several months afterwards, and a local
veterinarian (J. Causey pers. comm.) reported that a relatively high number of
cats with feline distemper were brought to his small animal clinic in Lake
Placid during the bobcat epizootic. Young (1958) noted that bobcats are
known to kill domestic cats. In addition, an unusual number of sick or dead
raccoons was observed within and in the vicinity of the study area from March
to May 1980, and bobcats were known to feed on raccoons in the study area
(see Food Habits section).
Although its reported incidence in wild felids in the United States is low
(Burridge et al. 1986), rabies also may be a significant mortality factor in
bobcat populations. In Florida, 11.1% (7 of 63) bobcats submitted for rabies
testing from 1975 to 1983 were positive for the disease, compared with 3.1-
9.7% for raccoons, foxes, and bats which are the principal vectors in the state
(Burridge et al. 1986). The actual prevalence of rabies in bobcat populations
may be higher than the available data suggest, as rabid bobcats may be less
likely to come to the attention of the public than rabid raccoons or foxes.
Longevity.- Radio-collared animals known to have survived beyond the
end of the study included females F1 and F8. F1 was last observed in May
1984 at an age of approximately 9 years, 10 months, and F8 was last observed
in December 1984 at an age of about 5.5 years.
Food Habits
Fourteen species of mammals and four species of birds were identified in
scats collected on the core portion of the study area (Table 3). Cottontail,
marsh rabbit, and cotton rat were the principal prey species, comprising 73%
of total prey items and 86% of estimated prey biomass. Although seasonal
differences in the frequency of these three species were not statistically
significant (X2 tests, p > 0.05), there were suggestive trends. The lowest
frequency (26%) of cottontail was in summer (June-August), compared with
38-42% in winter (December-February), spring (March-May), and fall
(September-November). Cotton rat showed a similar trend, with a frequency
of 16% in summer versus 21-29% in other seasons. Marsh rabbit was lower in
both summer (5%) and fall (0%) than in winter (8%) and spring (8%). The
reduced frequency of the three major prey species in summer was reflected in
an increased frequency (26% vs. 4-11% in other seasons) of other small
mammals (Glaucomys, Rattius, Peromyscus, Podomys, Oryzomys). The number
of mammal species represented in scats in different seasons was lowest in fall
(4 vs. 8-10 in other seasons). Separate and combined frequencies of cottontail,
Table 3. Animal food items in 146 bobcat scats collected on the core study area, 1967-1979.
Minimum % of Scats % Biomass
Scientific Common Number of % of Total Containing of All
Name Name Individuals Prey Items Prey Item Prey Items
MAMMALS 250 89.9 100.0 99.9
Sylvilagus floridanus Eastern cottontail 110 39.6 75.3 74.0
Sigmodon hispidus Hispid cotton rat 72 25.9 49.3 4.0
S. palustris Marsh rabbit 20 7.2 13.7 8.5
Podomys floridanus Florida mouse 11 4.0 7.5 0.2
Sciurus carolinensis Gray squirrel 10 3.6 6.8 1.8
Didelphis virginiana Opossum 5 1.8 3.4 6.2
Rattus rattus Black rat 4 1.4 2.7 0.2
Peromyscuspolionotus Oldfield mouse 4 1.4 2.7 <0.1
Glaucomys volans Southern flying squirrel 3 1.1 2.1 0.1
Oryzomyspalustris Marsh rice rat 3 1.1 2.1 0.1
Neofiber alleni Round-tailed muskrat 2 0.7 1.4 0.3
Procyon lotor Raccoon 2 0.7 1.4 3.6
Bos taurus Cow 1 0.4 0.7 *
Sus scrofa Pig 1 0.4 0.7
Unidentified Mammals 2 0.7 1.4
BIRDS 28 10.1 16.4 1.0
Colinus virginianus Northern bobwhite 2 0.7 1.4 0.2
Cyanocitta cristata Blue jay 1 0.4 0.7 <0.1
Gallus gallus Chicken 1 0.4 0.7 0.8
Sturnella magna Eastern meadowlark 1 0.4 0.7 <0.1
Unidentified Birds 23 8.3 15.8
* Assumed to be carrion
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
marsh rabbit, and cotton rat did not differ significantly (X2 tests, p > 0.05)
between years for years with adequate samples of scats (1971-1975, 1979).
Of the scats analyzed, 40% contained grass or other vegetation. In 9.6% of
the scats, vegetation comprised from 10 to 40% of the volume of the scat. The
high frequency and quantity of plant material in scats suggest that it was
intentionally consumed in some cases. Plant material had a frequency of
occurrence of 11% and comprised 4.4% of the volume of bobcat stomach
contents from other Florida localities (Maehr and Brady 1986). Young (1958)
noted that wild fruits, principally of cactus (Opuntia), occurred (5%) in a
Florida bobcat stomach collected in April. Kight (1962) reported that grass
made up 11.2% of the diet of bobcats in South Carolina and suggested that it
was deliberately rather than accidentally eaten.
In addition to the scat analysis, occasional observations were made on foods
and feeding behavior on the core study area. Bobcats were seen carrying a
cotton rat on one occasion and a black rat on another. The semi-tame
individual was once seen springing out of hiding in a palmetto thicket in an
unsuccessful attempt to catch a cottontail, and twice individuals were observed
chasing gray squirrels, once in a tree and once on the ground. On two days in
November 1979, Hope Ryden (pers. comm.) followed the semi-tame female
(Fl) in the field to observe her hunting methods. The cat tended to walk along
trails and would stop and listen intently when she heard a sound off the trail,
then stalk slowly in that direction. She once stalked an armadillo (Dasypus
novemcinctus) by sound, but lost interest when she saw what it was. On
another occasion, Ryden (1981) watched the bobcat kill a raccoon and take it
to her young. Another instance of predation on raccoons in the core area by a
different bobcat was observed by C. E. Winegarner (pers. comm.) in March
1982. A juvenile raccoon released from a live trap was caught by the bobcat as
it entered the woods a short distance away. The bobcat held the raccoon by
the throat as it squalled and struggled violently. The bobcat dropped the
raccoon when it saw the observer, but apparently returned and recaptured the
raccoon after the observer left the area, as he heard the raccoon squalling
again. In April 1982, a deer (Odocoileus virginianus) that had been hit by a car
was fed upon and sparsely covered with dry grass by a bobcat. The only record
of non-mammalian or avian prey of bobcats on the study area, was an
observation in July 1981 of the semi-tame female killing a large adult
southeastern five-lined skink (Eumeces inexpectatus). She slowly stalked the
lizard, which was moving around at the edge of a clump of palmettos, from
about 6 m away then rushed it from about 1.5 m. It ran under a pile of dry
grass and the bobcat spent 3-4 minutes chasing the lizard before she caught it.
She would stand still, listening intently, then pounce on a spot with her feet and
push her snout into the grass. After catching and killing the lizard she carried
it to a nearby shady spot, then abandoned it and moved on.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
The food habits data suggest that the diet of bobcats on the study area was
influenced both by prey availability and selection for certain species, based on
knowledge of habitat relationships and populations of vertebrates of the core
area (Layne unpubl. data). The predominant prey species, cottontail, was
common in drier habitats throughout the study area and frequently foraged in
the open on road shoulders and along trails. In contrast, marsh rabbits were
apparently less abundant than cottontails and largely restricted to dense grass
or palmetto thickets of seasonal ponds. They seldom foraged in the open and
when they did so rarely moved more than 1 m from the edge of dense cover.
In view of the lower numbers, more restricted habitat distribution, and
presumably less vulnerability to capture of this species, its high rank order in
the diet suggests it was hunted selectively by bobcats. Although generally
distributed throughout the study area and relatively abundant in habitats with
well-developed ground cover, the cotton rat was overall less abundant and
widespread on the study area than such smaller rodents as Peromyscus
gossypinus, P. polionotus, and Podomys floridanus, suggesting that its larger
size made it a more favored prey item. A number of potential prey species
were conspicuous for their absence in scats. The cotton mouse, P. gossypinus,
the most abundant and habitat-tolerant species on the study area was not
recorded in scats. Armadillos (Dasypus novemcinctus), also abundant in the
study area, did not appear in scats, and the observation cited above suggests
they were ignored when encountered. Also noteworthy was the absence in
scats of such ground-frequenting birds as common ground dove (Columbina
passerina), scrub jay (Aphelocoma coerulescens), rufous-sided towhee (Pipilo
erythrophthalmus), brown thrasher (Toxostoma rufum), and gray catbird
(Dumetella carolinensis) that are common seasonally or year-round in habitats
used by bobcats.
The data from this study agree with those from elsewhere in the range that
indicate the bobcat concentrates on medium-sized prey with some species of
lagomorph being a major food item (Rosenzweig 1966, McCord and Cardoza
1982). Cottontail, marsh rabbit, and cotton rat also predominated in previous
food habits studies of bobcats in other parts of Florida (Fickett 1971, Maehr
and Brady 1986). Data summarized by Maehr and Brady (1986) indicated that
bobcats in Florida and elsewhere in southeastern U.S. utilize deer less
frequently than in northeastern U.S.
Home Range and Social Organization
Home Range Size.- Mean overall home range size of 12 adult bobcats was
19.1 km2 (Table 4). Means and ranges of five male and seven female adults
were 25.5 km2 (14.8-31.1) and 14.5 km2 (8.9-21.6), respectively. Adult male
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 185
ranges were significantly larger (U5,7 = 3,p < 0.05, 2-tailed) than those of adult
females. The individuals were monitored from 16 to 1143 days (X = 465) and
located on 26%-94% (X = 44) of the days during the total period they were
tracked. The mean number of fixes per cat was 333 (range = 21-1248). The
shape of home ranges tended to be elliptical. Mean maximum range length
and width were 7.3 km (range = 5.3-9.0) and 5.1 km (range = 4.3-5.8),
respectively, for adult males and 5.2 km (range = 4.2-7.0) and 4.0 km (range =
2.6-6.6) for adult females (Table 4). Adult male ranges were significantly
longer (U = 4, p < 0.05, 2-tailed) than those of adult females, but there was
no sex difference in width (U = 7,p > 0.05, 2-tailed). The mean ratio of
length to width was 1.5 (range = 1.0-2.1) for adult males and 1.4 (range =
1.1-1.8) for adult females. The difference was not significant (U,7 = 15.5,
p > 0.05, 2-tailed).
Home range boundaries tended to coincide with such features as railroad
tracks, firelanes, roads, footpaths, and well-defined edges between natural and
man-modified habitats. When portions of the vacated range of a deceased
bobcat were occupied by surviving same-sexed neighbors or when a range
boundary shift occurred between two same-sexed bobcats, the new boundaries
were usually established along such distinctive habitat features. No
"exploratory" movements were detected. It is possible that with the relatively
intense tracking effort in this study visits to peripheral areas were regularly
recorded and thus the areas were recognized as part of the range, whereas with
less frequent monitoring movements to such outlying points might have been
regarded as "exploratory."
Observed short-term home ranges of adults with an adequate number of
locations in any of the 12 time periods to provide a reliable indication of
movements are given in Table 5. As in the case of overall home ranges, male
short-term ranges averaged larger (X = 15.5 km2, range = 11.8-22.0) than
those of females (X = 8.8 km2, range = 5.9-12.4). The difference was
significant (U57 = 2, p < 0.01, 2-tailed). Short-term ranges of males in
different time intervals were from 15 to 84% (X = 56) of their respective
overall home ranges, as compared with 32-87% (X = 60) for females). Ratios
of maximum to minimum short-term home ranges for individuals with
estimates in two or more time intervals averaged 0.61 (range = 0.24-0.91) for
five males and 0.62 (range = 0.39-0.84) for five females. The difference in
ranks of ratios for males and females was not significant (U = 12, p > 0.05,
2-tailed), indicating that there was no sex difference in relative variability of the
home range over time.
Short-term home range estimates did not exhibit any obvious seasonal
trends. Two young individuals (M6, F8) showed expansion of their home
ranges following independence from the mother. Observed home range size of
other individuals frequently changed abruptly from one time period to another.
A major cause of such changes was the death or disappearance of a neighbor.
Table 4. Overall home range areas and range axes of adult bobcats.
Home Range Axes (km)
Length Number Home
of of Number Range Maximum Maximum
Record Days of Are, Length Width Ratio
Individual (days) Located Locations (km ) (A) (B) (A/B)
MALES
M1 284 145 490 24.9 6.0 5.8 1.0
M2 184 64 196 14.8 5.3 4.6 1.2
M3 161 59 196 25.8 9.0 4.3 2.1
M6 690 231 517 31.0 8.4 5.0 1.7
M8 606 156 510 31.1 7.8 5.7 1.4
FEMALES
F1 1,143 426 1,248 18.2 5.2 4.5 1.2
F3 168 56 199 8.9 4.6 2.6 1.8
F4 497 257 600 19.4 7.0 6.6 1.1
F8 519 232 531 12.7 4.6 3.4 1.4
F9 699 251 466 21.6 6.8 4.2 1.6
F10 16 15 53 9.4 4.2 3.3 1.3
F11 258 121 171 11.6 4.2 3.6 1.2
Table 5. Home ranges (km2) of adult bobcats during 12 time intervals between April 1979 and August 1981. Values indicated by an asterisk are for
juveniles during the first period they were considered to occupy their own home range. Estimates in parentheses are considered too low as a result
of behavior of females with young litters (see text) and were not used in statistical calculations.
1979 1980 1981
28 Apr 1 Jul 26 Oct 17 Jan 6 Feb 29 Feb 1 May 20 Jul 8 Oct 1 Dec 9 Mar 1 Jul
to to to to to to to to to to to to
Individual 30 Jun 25 Oct 16 Jan 5 Feb 28 Feb 30 Apr 19 Jul 7 Oct 30 Nov 8 Mar 30 Jun 12 Aug
MALES
M1 12.2 10.2 15.1 18.2
M2 12.4 11.3 -
M3 12.3 17.1
M6 4.8* 5.8 16.0 18.2 19.8 19.2 20.3
M8 21.3 25.2 23.3 24.8 15.6
FEMALES
F1 11.0 11.5 10.6 14.0 (10.3) 13.8 12.9 12.4 12.9 12.9
F3 5.9 -
F4 10.9 10.4 7.0 6.8 11.7 (8.9) 11.0 8.6 -
F8 4.1* 4.8 5.2 7.9 9.8 10.4 -
F9 11.1 11.3 8.1 12.6 13.1 14.7 13.5 15.0
F10 8.2 -
F11 7.1 (2.3) 8.4 -
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
Such a case was that of adult male M6 who expanded his range approximately
175% within two weeks following the death of a presumed adjoining male.
Females with recently-born young in the period 1 May-19 July 1980 (Fl, F9,
Fl1) showed an apparent sharp decrease in home range size. However, as
described more fully in the following section, intensive monitoring of selected
females with small young indicated that they did not significantly reduce their
home range but rather visited their range boundaries for shorter periods of
time, resulting in a lower probability of detecting such longer movements.
Overall home ranges of adult males in this study averaged about 73% larger
than those of females, agreeing with data from throughout the species' range
indicating that adult male bobcats consistently have larger home ranges than
females (e.g. Bailey 1972, Berg 1979, Brittell et al. 1979, Buie et al. 1979,
Erickson and Hamilton 1980, Fuller et al. 1984, Gould 1980, Hall 1973,
Kitchings and Story 1984, Lancia et al. 1986, Lawhead 1978, 1984, Lembeck
1978, Miller 1980). From observations of tracks independent of this study,
Winegarner (1985a) obtained home range estimates for the semi-tame female
(Fl) of 4.68-6.45 km2 from about May 1980 to May 1981. In contrast, our
estimates of home range of this individual during five time intervals over the
same year ranged from 10.3 to 13.8 km2 (X = 12.4 km2). The marked
discrepancy in the home range estimates of the two studies apparently reflects
the increased resolution of movements provided by radiotracking
supplemented by trailing and perhaps also a difference in the intensity of
monitoring. Mean range size of males in this study was considerably smaller
than that (44.4 km2) reported for two males in northeastern Florida (Progulske
1982), the only other available data on home range size of bobcats elsewhere in
the state. Mean home ranges of adult bobcats determined by radiotelemetry
and calculated by the minimum home range method from other geographic
regions (Alabama, Arizona, California, Louisiana, Minnesota, Nevada, South
Carolina, Tennessee) ranged from 2.6 to 50.4 km2 for males and from 1.1 to
77.0 km2 for females (Berg 1979, Buie et al. 1979, Fuller et al. 1984, Golden
1982, Hall 1973, Kitchings and Story 1984, Lawhead 1984, Miller 1980). The
great variability in bobcat home range size in different parts of the range
undoubtedly reflects both variation in methods of study, as well as
environmental factors. On the basis of present data, little can be concluded
concerning general trends in bobcat home range size related to habitat or
geographic region, although the largest reported home range sizes tend to be
in northern and western populations.
The influence of habitat features on movements of bobcats and hence on
home range size and use seen in this study also has been observed by other
workers. Buie et al. (1979) found that home ranges generally interfaced along
roads, railroads, and water ways. Most fixes obtained by Hall (1973) were
within a few hundred meters of a road or trail, and Miller (1980) stated that
bobcats rapidly accepted and utilized logging roads, firelanes, and farm roads
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 189
as avenues of travel. High levels of use of unpaved roads and similar features
may be related to higher abundance of prey along their edges coupled with a
better opportunity for a stealthier approach as compared to stalking in more
dense areas (see Food Habits section).
In south-central Florida, Alabama (Miller 1980), and presumably elsewhere
in the southeast, an abundance of suitable rest sites provided by dense thickets,
vine-covered areas, patches of palmettos, etc. may allow less restricted
movements than some other regions. For example, McCord (1974) stated that
in an area in Massachusetts ledges were important to bobcats and their
location was a factor influencing bobcat movements; and in relatively
sparsely-vegetated areas in Idaho (Bailey 1972) and California (Zezulak and
Schwab 1979) bobcats tended to occur in areas with rock falls, caves, and other
such features. In severe weather, movements were even more restricted to
these areas, which were in high demand and were frequently shared among
several cats.
Use of Area Within Home Ranges.- Based on the distribution of radio
fixes in 4-ha quadrats, adults visited from 10 to 62% of the area in their overall
home ranges. Males appeared to use their home ranges less thoroughly than
did females. Five males were recorded in from 14 to 34% (X = 27) of their
home range quadrats compared with 10-62% (X = 40) for seven females,
although the difference was not significant (U = 7,p > 0.05, 2-tailed). About
47% of the quadrats visited by females contained more than one fix, as
compared with only 29% for males. As in the case of the proportion of
quadrats used, this difference points to more intensive utilization of the home
range by females. The highest number of locations in a single quadrat
recorded for any individual was 59 for the semi-tame female F1 in the quadrat
including the dwelling at which she was occasionally fed and often rested. The
distribution of her locations outside of this area was not obviously different
from that of other females in the population.
Comparison of the distributions of active and inactive (= rest sites)
locations, indicates that, although inactive locations occurred throughout the
range, there was a tendency for them to be clumped into 2-6 vaguely defined
areas near the periphery of the home range. An average of 42% (range =
32-51) of the home range quadrats used by females contained rest sites,
compared with 27% (range = 17-36) for males, indicating that females used
relatively more areas within the home range for resting. Of quadrats with
fixes, an average of 17% of those in both male and female home ranges
contained only rest sites. Thus there appeared to be no sex difference in the
relative proportion of the home range area used only for resting.
Relationships Between Adult Home Ranges.- Figures 3-5 show the spatial
relationships of bobcats in the core area during the 12 time intervals from 28
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
April 1979 to 12 August 1981 as determined by radiotracking, trailing, and
visual observations. The general locations of all presumed resident bobcats are
indicated. These include individuals radiotracked during the interval as well as
marked cats whose collars had stopped transmitting and unmarked animals
known or believed to be present on the basis of tracks or sightings.
Configuration of home ranges varied continuously throughout the study but
tended to be relatively more stable during the initial (April-October 1979) and
final (March-August 1981) periods than during the interval from winter
1979-80 to spring 1981. Although the shape and size of home ranges of
individual resident bobcats varied over time, the cats exhibited a strong
tendency to remain in the same general area. Two females occupied the same
overall home range for periods of about 5.5 years (F8) and 9 years (Fl). Of
the 13 adults monitored during the study, one exhibited a local home range
shift and one made a long-distance movement. In the first case, an adult
female (F3) apparently moved to an area adjacent to her original home range.
In August 1982 she was killed on a highway about 1.5 km N of the nearest
boundary of the home range she had occupied from June through November
1979, when her collar failed. She continued to use the area at least through
December, based on tracking. Sightings believed to be of this individual were
made at the edge of her previously known range in February and August 1980.
The male (M6) and female (F8) juveniles of this female remained in the natal
range, and the daughter produced her first litter in May 1980. On the
assumption that two breeding females would not occupy the same area, the old
adult must have vacated her former range by spring 1980 or before. The
long-distance movement involved a male (M7). He was trapped and marked in
late April 1980 and radiotracked for 3 days following release, after which the
transmitter failed. He was sighted 20 August 1980 and 3 June 1981 within 2 km
of the area in which he was tracked in April 1980, indicating he was still in the
study area after 14 months but may have shifted his home range. In July 1982,
he was found dead on a highway 70 km from the study area. The distance
moved by this individual exceeds values previously reported from the southeast
(Griffith et al. 1980, Kitchings and Story 1984). Knick and Bailey (1986) noted
that the longest documented bobcat movements (158 and 182 km) were from a
region with a cyclic prey base and that in areas, including the southeast,
characterized by a stable prey base movements have been < 50 km.
Neither resident adult males nor females showed appreciable home range
overlap with adjacent bobcats of the same sex. The overlap of adjacent adult
male home ranges believed to be relatively accurately delimited averaged 5%,
with a range of 1-11%. Mean and extremes of home range overlap of adult
females were 3 and 0-17%, respectively. These values indicate that in both
males and females adults of the same sex tended to have exclusive home
ranges. Tracking of neighbors, radio fixes, and sightings suggested that, in
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
general, mutual use of areas by adult bobcats of the same sex was confined to a
narrow zone along the line of contact of their current home range boundaries.
Bobcats apparently only rarely came into close contact with neighbors of
the same sex. Only four cases of two adult males or two adult females being in
close proximity were recorded during the study. Daytime rest sites of females
F4 and F1 were within 200 m of each other on one occasion in December 1979,
and F4 rested near F8 on one day in October 1980. These two females also
walked within 100 m of each other one night in August 1980. The only instance
of two adult males being close together was recorded in October 1980, when
M8 followed M6 about 2 minutes behind along a stretch of railroad track, then
each veered off in a different direction.
Death or disappearance of a resident bobcat resulted in major changes in
the size and shape of home ranges of adjacent animals of the same sex. In
contrast, opposite-sexed survivors did not exhibit such a response to the loss of
a neighbor. Thus spacing mechanisms may operate independently in males
and females. Three clear-cut examples and a probable fourth case of this
phenomenon were documented. After the death of M2 in late October 1979,
adjoining males M1 and M3 expanded their home ranges into the area of M2's
former range, whereas the boundaries of the female (Fl, F3, F4) ranges
remained stable (Fig. 3B, C). The apparent expansion of Fl's range reflects
better sampling in the subsequent time period and not an actual change in
movements. M3 died in mid-January 1980, and his death was followed by
further expansion of Ml's range but no obvious changes in those of females
(Fig. 3C, D). Female ranges also remained stable following the death of Ml in
early February 1980 (Fig. 3D, Fig. 4A). The most dramatic male range
expansion documented was that of M6 in late July 1980, following the death of
an unmarked adult male on the north boundary of his range (Fig. 4C, D).
Female ranges also showed an apparent slight increase during this period,
which is believed to reflect changes in their movements related to age of their
young rather than an actual expansion in response to the increase of M6's
range. In the single case of a confirmed death of a female (F10, late February
1980), one (F4) of two neighboring females markedly expanded her range into
the vacated area (Fig. 4A, B). The other female (Fl) was also subsequently
located in the former area of F10, but data available on F10 up to the time of
her death were not complete enough to definitely establish the boundary
between the home ranges of these individuals.
Range expansion of adjoining same-sexed bobcats began a short time after
the death of a resident. In six cases, such shifts were first detected within 5-14
days, with a mean of 9 days. There was no significant difference (U2,4 = 4,p >
0.05, 2-tailed) between sexes in the time before the first recorded incursion into
the new area. Home range boundaries in the invaded area appeared to be
realigned within several weeks with no evidence of "jockeying" for position.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
I
F
M3?
A
8 APR-30 JUN
1 JUL-25 OCT
,J C
26 OCT-16 JAN
0 1 2
km
1J.' D
17 JAN-6 FEB
Figure 3. Bobcat home ranges during four time intervals between 28 April 1979 and 5
February 1980. (A) 28 April-30 June 1979; (B) 1 July-25 October 1979; (C) 26 October
1979-16 January 1980; (D) 17 January-5 February 1980. Observed boundaries of home ranges of
adult males and females alive during a given period are shown in heavy and light solid lines,
respectively. Ranges of adult males and females that died or vacated their range in the period
just preceding a given interval are shown by heavy and light broken lines. Females with young
during the interval are indicated with an asterisk. Other individuals known or assumed to be
present on the basis of circumstantial evidence, but whose ranges could not be estimated, are
included without indication of home range boundaries. Individuals first captured during a given
period are underlined. Individuals believed to have been seen after radio collars failed are
overlined. Two lakes in the northern end of the study area are also shown.
F10?
*
F9?
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
In contrast to the intrasexual exclusiveness of home ranges, adult male
ranges were typically superimposed on those of adult females (Figs. 3-5). In
the majority of cases, a single smaller female range was largely or entirely
contained within the larger home range of a male, with the relationship
persisting until one of the individuals died. Of nine combinations of
male/female home range overlap (Figs. 3-5), six involved a male and a single
female (M1/F1, M2/F4, M3/F3 during the period 1 July-25 October 1979,
M7/F1 from 29 February to 30 April 1980, M6/F8 from 29 February 1980 to
8 March 1981, and M8/F1 from 20 July 1981 to 12 August 1981). One of these
pairs involved probable siblings (M6, F8). The remaining combinations
consisted of a male and two or three females (M1/F1,F4 and M3/F3,F4 from
26 October 1979 to 16 January 1980 and M1/F1,F3,F4 from 17 January to 5
February 1980). In addition to containing the range of his probable sister,
M6's range may also have overlapped that of his mother (F3) during the period
20 July 1980-12 August 1981 (Figs. 4D, 5). The number of different males with
which a given female was known to associate during the study ranged from 1 to
3.
Three pair relationships (M1/F1, M2/F4, M3/F3) existed on the core
region of the study area during the early period of the study after a sufficient
number of radio fixes had been accumulated to give a reasonably reliable
picture of home range configurations (Fig. 3B). The range shown for F1 in
Fig. 3B was based on relatively few fixes. Prior to being equipped with a
radio-collar she was tracked farther to the west than shown by the telemetry
data and probably used a major part of the range of M1 during the 1 July-25
October 1979 interval. Although the M7/F1 pair (Fig. 4B) appears to be the
reverse of the usual case of a larger male range with a contained smaller
female range, the range shown for M7 is based on only seven radio locations
and is undoubtedly less than his actual range. Because of collar failure, this
animal could not be tracked in subsequent periods. Following the collar failure
and apparent disappearance of M7 from the range of F1 in late spring 1980,
adult male M8 aligned his range boundary with that of F1 (Fig. 4D) such that
about 97% of Fl's area was contained within about 49% of M8's range. This
configuration persisted until early March 1981 (Fig. 5A, B), after which the
male gradually ceased movements in the western portion of his range. As a
result, all of Fl's observed range was contained within about 83% of the male's
range by summer 1981 (Fig. 5D).
Two male-female associations involving more than one female, were
established following the death of M2 on 25 October (Fig. 3C). Male M1,
initially associated only with female Fl, extended his range to also overlap a
portion of that of female F4, who had been associated only with M2 prior to his
death. During the same period, M3 also extended his range to encompass part
of F4's. M3's previous female associate (F3) could not be radiotracked after 15
November 1979 because of collar failure. However, tracks, sightings, and the
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
29 FEB-30 APR
6 FEB-28 FEB
F9 F9
F3?
M? F4 M? M? F4 Me
F8
F8
CM M8 D
20 JUL-7 OCT
M7? 1MAY-19 JUL 'Lk M?
F9 F9
F1LJI F11
Figure 4. Bobcat home ranges during four time intervals from 6 February to 7 October 1980.
(A) 6-28 February; (B) 29 February-30 April; (C) 1 May-19 July, (D) 20 July-7 October.
Arrow indicates home range shift. See Figure 3 for description of other symbols. M6 and F8
(captured in January 1980), presumed to be young of F3 and present since beginning of study,
first considered as adults in the 29 February-30 April interval.
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 195
pattern of movements of her radio-collared young (M5, M6, F8) indicated that
she was probably still in the area through February 1980. Her range is shown
in Figure 3C as similar to that of the previous period based on radio locations
through mid-November, and she is shown as present in the same general area
in Figures 3D and 4A. Following the death of M3, M1 expanded his range,
probably to overlap or include that of F3 (Fig. 3D), as F3 is assumed to have
remained in her former range until February 1980. Thus, during 17 January-5
February 1980 M1's range probably overlapped all or major portions of the
ranges of three adult females (Fl, F3, F4), two of which (Fl, F3) had young. It
may be significant that while the range of male M1 was superimposed on those
of more than one female, the greatest overlap was with the female Fl, with
which he was originally associated.
Although the ranges of given males and females overlapped and both
individuals were known to use the same places within the common area,
observations indicated that for the most part they did not visit the same sites at
the same time, i.e. they were spatially associated but tended to be temporally
isolated. However, males and females were occasionally located in close
proximity, if not actually together. Instances of such close association were
recorded in every month of the year except June and July, during which time
less radiotracking was done and fewer marked male/female combinations were
present in the population. These data indicate that adult males and females
with overlapping ranges did associate, if only infrequently, outside of the
breeding season.
Observations suggested that the male of a pair may keep other males from
a female with small young. During the night of 5 April 1981, an adult male
(M6) adjacent to the M8/F1 range (Fig. 5C) was located less than 200 m from
the den of F1 with her recently-born litter. After spending about 2 hours in the
area of the den, he moved about 1 km SSE, passing through the area near the
cottage where F1 was occasionally fed and which was one of her preferred rest
areas. During the night of 8-9 April, he also passed within 0.5 km of the den.
Immediately following M6's appearance in the vicinity of the den and cottage,
M8 began to concentrate his activity in these areas, moving through and resting
in them during the day and night. Although no actual contact between the two
males was documented, it is possible that M8's behavior was a response to the
presence of M6 in the vicinity of the den and may have served to discourage
further visits by M6 to the den area. Lembeck (1986) reported several cases
where males (sometimes more than one) were in close proximity to a female
for a few days following parturition.
The adult male also may promote the dispersal of older juveniles. When
not in the area of the den or cottage, M8 could usually be found moving along
the periphery of other portions of his and Fl's shared range, particularly in the
area apparently used by an older kitten of F1 that was still in the natal range.
On four of five days during the first two weeks of April that the juvenile was
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
MT7 8 OCT-30 NOV \ ..... 1 DEC-8 MAR
F9 F9
F11 F11
Fll l 1?
SF3? F3?
M? F4? M? F4?
M6 M6
M F1F
M8
S C D
9 MAR-30 JUN 1 JUL-12 AUG
F9 F9
0 1 2 *
km
Figure 5. Bobcat home ranges during four time intervals from 8 October 1980 to 12 August
1981. (A) 8 October-30 November; (B) 1 December 1980-8 March 1981; (C) 9 March-30 June;
(D) 1 July-12 August. Arrow indicates long-distance movement. See Figure 3 for description of
other symbols.
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
trailed or seen along or close to the edge of the home range, tracks were found
that suggested that it had been in contact with M8. No signs of fighting were
noted, but on all occasions of apparent contact between these individuals there
were many, frequently overlapping, tracks scattered over a wide area. Tracks
of the juvenile were not seen in the area following the last of the apparent
contacts with M8, suggesting that it may have dispersed. If this interpretation
is correct, its dispersal may have been hastened by the contacts with the adult
male.
The number and complexity of social and ecological factors that may
potentially affect home range size and configuration, the small number of
bobcats studied, and the relatively high turn-over of adults leading to
considerable instability of the population during a major part of the study make
it difficult to partition the causes of the observed variation in home range size
and spatial relationships. However, death of individuals, relationships between
adult males and females, and the mother-young relationship appeared to be
important factors affecting the spatial organization of the population. Death of
a resident influenced home range size of adjacent individuals of the same sex.
Bailey (1972) and Miller (1980) also observed marked expansion of home
ranges of neighboring bobcats of the same sex upon the death or
disappearance of a resident. In contrast, however, Anderson (1986) reported
that a male that shifted his home range into the area previously occupied by an
experimentally removed male exhibited decreased home range size following
the shift. Seasonal changes in range size of individual bobcats also have been
reported by Buie et al. (1979), Kitchings and Story (1979), Lembeck (1978),
and Zezulak and Schwab (1979).
The low degree of male-male and female-female home range overlap
observed in this study indicates that residents of the same sex occupied
mutually exclusive ranges. Similar range separation of adjacent same-sexed
individuals also has been reported elsewhere in the range (Bailey 1972 in
Idaho, Brittell et al. 1979 in Washington, Buie et al. 1979 in South Carolina).
Erickson and Hamilton (1980) in Missouri, Lawhead (1978) in Arizona, and
Lembeck (1978) in California reported that males showed substantial range
overlap while females did not, whereas in another California study both males
and females showed substantial range overlap (Zezulak and Schwab 1979). In
contrast, male and female ranges usually exhibit extensive overlap (Berg 1979,
Brittell et al. 1979, Buie et al. 1979, Erickson and Hamilton 1980, Karpowitz
and Flinders 1979, Kitchings and Story 1979, Marshall 1969, Miller 1980). In
this study the home range of a female usually was contained within a larger
male range. This configuration apparently reflected a persistent, loose pair
bond, the individuals not only associating together for mating but also
maintaining social integration during the nonbreeding season. Such a
relationship appears to fit Kleiman's (1977) definition of facultative
monogamy. In the cases in which a single male home range overlapped the
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
ranges of more than one female, it tended to include a greater share of the
range of one female than of the others, suggesting a closer relationship with
some females than others. Male-female associations involving more than one
female occurred during the period of increased mortality, particularly among
males, and may have reflected the shortage of males and instability of the
population at that time.
In addition to increased accessibility of a mate, the observed tendency of
association between a single male and female could have other adaptive
advantages. The male may serve to protect food and other resources for the
female and young within his range by inhibiting encroachment by other males.
The male may also aid in protecting young from predation, including
cannibalism by other males (Crowe 1974, Erickson 1955). In this study, the
increased presence of an adult male (M8) in the areas frequented by the
female (Fl) and her young litter within his home range following visits by the
male (M6) from an adjacent territory may be an example of a resident male
attempting to prevent an outsider from disturbing the young litter of his mate.
As suggested above, the male also may encourage dispersal of older juveniles
from their natal range thus reducing possible competition for food for the next
litter and contributing to the dispersion of the population. Marshall's (1969)
observation of an adult and a juvenile male bobcat growling and spitting at
each other (possibly over food), with the larger male pursuing the smaller one,
also may have been a case of an adult male interacting with a juvenile near
dispersal age. Although studies in recent years have produced no evidence that
male bobcats play a direct role in care of offspring, Young (1958) alleged that
both parents may bring food to the young before and after the den is
abandoned when kittens are about 2 months old.
As noted by McCord and Cardoza (1982), present evidence indicates
considerable flexibility in bobcat social structure. This applies to felids in
general (Eisenberg 1986). Although some of the reported variation in spatial
relationships may be due to differences in methods of study or insufficient
data, actual differences within the same population at different times and
between populations in different regions or habitats probably reflect variation
in food resources, mortality patterns, weather conditions, and other ecological
factors. Although specific correlations between bobcat social organization and
demographic characteristics or environmental conditions remain to be
demonstrated, it is possible that the tendency for males and females to be
associated in pairs is characteristic of stable populations with a good prey base.
Female-Young Behavior and Home Range Use.- Five family groups
involving three females and five litters were monitored until the young had
apparently dispersed. These young associated with their mothers for 8-11 (X
= 9) months. For the first 1.5-2 months after birth, while the kittens were
immobile, the movements of the mothers were more restricted, although they
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
continued to use their entire home range. The most detailed record of adult
female movements shortly after parturition was obtained for F1 (Fig. 5C, 6),
who was monitored intensively from 8 to 14 April 1981 after birth of a litter on
or about 1 April. During this period, she covered the entire area she used
prior to parturition and after the young were 3-4 months old (Fig. 6). On two
afternoons she made short trips to the nearest range boundary, and on four
nights between 1800 and 0100 hr she made long distance movements that
involved travel over most of the other portions of her pre-parturition range.
On one of these extended excursions, she rested for about 30 minutes at a site
1 km from the natal den area then returned directly to the den.
Maximum distances moved by adult females from natal and secondary den
sites during the first two months postpartum usually occurred in late afternoon
and at night. Because calculations of home ranges of females Fl, F9, and Fll
with newborn young during the period of 1 May-19 July 1980 were based
largely on radio locations during morning and afternoon, their observed home
ranges (Table 5) during this interval are probably underestimates of the areas
actually used.
The mothers apparently carried the kittens short distances to new rest sites
every 1-6 days, as no kitten tracks were observed where adults crossed sand
roads between consecutive known sites. The best example of this pattern of
rest-site shifting was obtained for F9 (Fig. 7) during the first 30 days after the
birth of her 1980 litter. In this period she used eight sites an average of four
(range = 1-6) days each. Mean and extreme distances moved between sites
were 0.3 km and 0.1-0.4 km, respectively. The total area within the polygon
defined by the perimeter rest sites was about 0.4 km2. At least six other sites in
the immediate vicinity were used during the second month after the birth of
the litter. The semi-tame female (Fl) also moved her litters about in a similar
fashion. For example, at least six sites were used during the first 51 days after
the birth of her May 1980 litter. All sites were within an area of about 0.3 km2.
She apparently made her first long distance movement (1.8 km) with the
kittens on 22 June in response to disturbance by farm machinery in the
immediate vicinity of the rest site used during the preceding few days.
Winegarner (1985b) also observed similar shifts in rest sites of F1 with young
about 1 month old in 1982.
Adults with kittens ranging from about 2 to 4 months of age also used rest
sites for periods of 1-6 days. The rest sites during this period tended to be
more generally dispersed throughout the adult's range than earlier. The
kittens sometimes accompanied the mother on short excursions in the vicinity
of the rest site. On several occasions females with kittens over 2 months of age
were observed carrying food to the rest site area. The family usually travelled
between rest sites with the mother in the lead and the kittens following
single-file. During this period the mothers continued to make independent
excursions along the boundaries of their range and occasionally used a rest site
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
HOME Ri
Natal den site' ,/"
//
-
0 .5
km
ANGE: 1 Dec 80-8 Ma
1 Jul 81-12 Au
Lr 81
i 81
MOVEMENTS:
(pm-am)
8-14 APR 81
----8-9
......... 9-10
- 10-11
----11-12
-- 12-13
---13-14
Figure 6. Movements of adult female F1 over a 6-day period following birth of a litter on or
about 1 April 1981.
/ I II (jI
,' firelane ,
fir ne-----------------------
I 5I
--- -
I 00
pav e d.
I*4
2-4 I
0I> 0l11
-^ II--^/^ --'"
-3- i- I
Figure 7. Pattern of den site use by an adult female (F9) following birth of a litter in April 1980. Key to symbols: triangle = natal den site;
numbered solid circles = secondary den sites used the first month and number of days spent at each site based on daytime resting fixes of the adult;
squares = presumed secondary den sites on six days during the second month.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
separate from that of the kittens. In some instances the adult rest site was on
the opposite side of the range from that of the young.
Females with kittens over 4 months old continued independent movements
throughout their ranges but also were frequently accompanied by kittens when
traveling. These family group movements often included trips along home
range boundaries. The adults continued occasionally to rest separately from
the kittens. When adults were not present, kittens made independent
excursions around the general area of the rest site. On several occasions when
she had kittens 5 months of age or older, F1 was recorded (visual observations,
tracking) traveling without her full litter, indicating that young at this age may
not remain together in the same area while the female is away. By 5-7 months
of age, kittens traveling with the mother often walked abreast or preceded her
along the route. Signs of apparent play were most noticeable during this
period. Based on tracks, one young would frequently move ahead along a
travel route and then "ambush" the others when they came past. Mothers also
participated in such play, as recorded at night on 16 September 1979. F1 and
her three young about 5.5 months old were observed for 20 minutes in the light
of vehicle headlights as they engaged in mock attacks on each other. The
juveniles were intent on ambushing one another, one jumping on the back of
another from behind a bush as it walked past. The attacks were usually
followed by a short chase, with either animal being the pursuer. A kitten also
would occasionally jump on the mother who would then chase it. The family
moved slowly along as they engaged in this play. Radio fixes, tracks, and
sightings indicated that young made occasional contact with adult males
beginning about their fifth month.
From about 7 months until they dispersed, juveniles were increasingly
independent of the mother. The family did not use a given rest site for more
than a day or two, and successive sites were often located on opposite sides of
the home range. The family group frequently traveled throughout all parts of
the range. Juveniles also wandered about more on their own, their individual
rest sites being up to 0.5 km apart. On several occasions when her older young
were resting at scattered sites, Fl was radiotracked as she moved through the
area to round them up. On 6 July 1981, L. Saul (pers. comm.) observed F1
giving 23 sheep-like "m-a-a" vocalizations in a 2-minute interval after which
three or four young appeared and followed her as she left the area. The
vocalizations were distinctly audible from a distance of about 60 m. On
occasion, when a mother was moving about the range with some of her young,
others would be located in a distant part of the range. Such instances became
increasingly frequent as the young neared the age of dispersal.
In one case, F1 and her two young born in 1980, the juveniles apparently
restricted their movements to separate areas at the periphery of the adult's
range from about 10 months of age (January 1981) until disappearing 3 or 4
months later. The only occasion during this period when they were recorded
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 203
elsewhere in the natal range was on 22 February when their tracks were found
together in a region of the adult range 1 and 3 km from their respective areas.
We last observed tracks of the juveniles within the mother's range in mid-
April, and Winegarner (1985a) could not find their tracks in June and July.
The adult gave birth to a new litter on or about 1 April, indicating that females
may mate and bear young while juveniles of their previous litter are still within
the natal range. Adult female F1 also was apparently still associated with one
or more juveniles of her April 1981 litter in December 1981 after the birth of a
new litter in mid-October, based on observations of her tracks accompanied by
those of a young individual. Evidence for breeding while still associated with
young of the last litter was not confined to the semi-tame female. F9 was
observed on 30 November 1980 with one of her two kittens born in mid-April
and gave birth to her next litter in early January 1981. Based on a 2-month
gestation period (McCord and Cardoza 1982) mating probably occurred in
early November.
Winegarner (1985a) also monitored female F1 and her older young in 1981
(see above) by means of tracks. She believed that the mother actually
abandoned the portions of her range occupied by the juveniles, then
reoccupied the areas following dispersal of the young. She concluded,
therefore, that dispersal of juvenile bobcats is preceded by "a period of
solitude" in the natal home range and this "temporary tenure" of the young in
the mother's range "insures that the home range is occupied." Although she
did not elaborate as to why establishment of exclusive home ranges by young at
the edge of the adult female's range is necessary to insure its occupancy, she
may have assumed that breeding females during late pregnancy and early
postnatal care of the young reduce their home range and that the presence of
their older young at the periphery helps to hold the area against other bobcats
so that the female can reoccupy it when her new litter is old enough to travel
with her. Our combined radiotracking and trailing data do not support this
interpretation. Although the female tended to visit the periphery of her range
less frequently and for shorter periods for about 2 months after the birth of her
litter in April, radio fixes regularly placed her in the area where the activity of
the juveniles was concentrated during this period. In addition, by searching for
her tracks in areas where she had been radio located the previous night, it was
confirmed that she continued to mark her former range boundary in these
areas. Although the last contact between F1 and her old juveniles, based on
close proximity of adult and juvenile tracks, recorded by Winegarner (1985a)
was in late January, we observed evidence of the adult and one or both young
in the same area on two nights in late February. On one of these occasions the
female and both young were in an area remote from the areas in which the
young were usually found (see above). Our data, therefore, indicate that the
young did not establish exclusive home ranges prior to dispersing from the
natal area and suggest that the young probably did not play a significant role in
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
maintaining the boundaries of the adult female's home range. Even if young
on the periphery of the adult range were effective in preventing encroachment
on the adult's range by other bobcats, only a relatively small fraction of the
total range perimeter would be "protected." The tendency of the young to
concentrate their activity at the periphery of the natal range during the late
pregnancy and postnatal period of the mother may have been due to the
combination of their age and the increased aggressiveness of the mother during
the breeding season. In this connection, Winegarner (1985a) once observed
the semi-tame female attacking one of her older young when it returned to "her
domain."
There are few comparative data on movements of bobcat family groups in
other parts of the geographic range. The best description is that of Bailey
(1979) for Idaho bobcats. General patterns in the movements of Florida
kittens were similar to those observed in Idaho in that movements were
generally restricted to den areas until the kittens were past 3 months of age.
After this age, more of the range was used by the offspring. In South Carolina,
Marshall (1969), found that an older juvenile used the entire range of its
mother, and Kitchings and Story (1979) reported the same behavior for a
juvenile in eastern Tennessee.
Few data were obtained on dispersal and establishment of home ranges by
juveniles, but we believe that most moved out of the study area. However, one
apparent case of a male (M6) and a female (F8) of the same litter becoming
established as a breeding pair in the natal range was recorded. These
presumed young of F3 remained in the mother's range after the deaths of the
overlapping adult males (Ml, M3) and abandonment of the range by the
mother. With time, both individuals extended their movements beyond the
natal range, and the female had litters in spring 1980 and 1981. The northward
expansion of the male's range apparently coincided with the disappearance of
an unmarked male in that area and probably resulted in overlapping part or all
of the range of his mother (F3), who had shifted her range into the area earlier
(Figs. 4D-5D).
Little information is available on dispersal and subsequent home range
establishment of young bobcats in other geographic regions. Bailey (1974) in
Idaho noted that young bobcats appeared to avoid settling in areas occupied by
residents and recovered five tagged kittens 1-2 years later as adults from sites
outside the study area, although he had no data on their movements during the
intervening period. Two subadults radiotracked in South Carolina by Griffith
et al. (1980) abandoned their initial activity areas (in the natal range?) in early
spring and began a pattern of movements involving temporary localization of
activity for varying periods of time. They concluded that their data supported a
model of subadult bobcat dispersal characterized by "nomadic search for
unoccupied, resource-adequate home range sites," as implied by Bailey (1974).
The tendency of the subadults monitored by Griffith et al. (1980) to use
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 205
temporary activity areas in the course of their long-term movements is
reminiscent of the localization of movements within the natal range of older
juveniles prior to their disappearance observed in this study. This behavior
may be a normal precursor to dispersal of young bobcats from their mother's
home range. The data for male M7 (see above), although sparse, suggest that
his movements might also have followed the pattern of temporarily localized
activity in the course of long-distance wandering exhibited by the subadults
studied by Griffith et al. (1980).
Daily Travel
Adult males tended to move greater distances from one day to the next
than did adult females, and juvenile movements were more restricted than
those of adult females (Fig. 8). The average day-to-day distance moved by all
bobcats was 1.6 km. Means and ranges of day-to-day movements of adult
males, adult females, and juveniles were 2.1 km (0-7.6), 1.4 km (0-6.6), and 1.0
km (0-4.2), respectively. Mean distances moved by individual males were
significantly greater than those of adult females (U67 = 4.5, p < 0.05, 2-tailed),
and juvenile means were significantly lower than those of adult females (U57 =
2.5, p < 0.05, 2-tailed). The ratio of mean adult male to mean adult female
day-to-day movements (1.5:1) was roughly proportional to the ratio of their
respective mean overall home range sizes (1.8:1).
Longer day-to-day movements of males compared to females also were
reported in other southeastern studies. Distances were 8.7 km for males versus
6.3 km for females (ratio 1.4:1) in South Carolina (Buie et al. 1979), 4.5 versus
1.2 km (ratio 3.8:1) in Tennessee (Kitchings and Story 1979), and 4.4 versus 2.9
km (ratio 1.5:1) in Louisiana (Hall and Newsom 1976). Ratios of male to
female home range sizes in these studies were 2.0:1, 3.7:1, and 4.9:1,
respectively. Straight-line day-to-day movements of males (2.2 km) and females
(1.4 km) in Louisiana (Hall 1973) were about half the summed successive
distances between captures (Hall and Newsom 1976), but the ratios were
similar (1.6:1 vs. 1.5:1).
The same general correspondence between ratios of day-to-day movements
and home range size of males and females also has been found in most studies
in other parts of the range. In Minnesota, the ratio (1.6:1) of mean
week-to-week distances moved by adult males (4.3 km) and adult females (2.6
km) was the same as the home range size ratio. Mean day-to-day distances
moved by male and female adults in Idaho were 1.8 km and 1.2 km,
respectively, a ratio of 1.5:1 compared with 2.2:1 for mean home range sizes
(Bailey 1972). Lawhead (1978) reported mean day-to-day movements of 1.2
km for adult males and 0.9 km for adult females (1.3:1), while the male to
-Adult males
---- Adult females
-- Juveniles
0.8 1.6 2.4 3.2 4.0 4.8 5.6 6.4
1.1 1.9 2.7 3.5 4.3 5.1 5.9 6.7
DISTANCE MOVED (KM)
Figure 8. Percentage distribution of day-to-day distances moved by adult and juvenile bobcats.
7.2
7.5
0 +-
0
0.3
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
female mean range size ratio was 2.1:1. The general trend of a lower male to
female movement ratio than home range ratio shown by these data indicates,
as suggested by the authors, that although males tend to have larger ranges
than females, females tend to move around within their ranges proportionately
more than males.
The means of day-to-day movements of adult males from December to
February, March to May, June to August, and September to November were
2.5, 1.9, 2.1, and 2.1 km, respectively. Corresponding values for adult females
were 1.6, 1.4, 1.2, and 1.4 km. Mean daily juvenile movements in fall, winter,
and spring were 0.9, 1.1, and 1.3 km, respectively. Mean day-to-day movements
of adult males during December-February were significantly greater (U =
2.5, p < 0.05, 1-tailed) than those during March-May but did not differ from
other seasons. The only significant seasonal difference in adult female
movements was between December-February and June-August (U56 5.5, p
< 0.05, 1-tailed). Small sample sizes prevented statistical comparisons of
juvenile seasonal movements. Daily distances moved by juveniles 8-10 months
old averaged 22% greater than those of juveniles 5-7 months old (U -= 6,p <
0.05, 1-tailed), reflecting the greater amount of travelling of older young with
the mother.
In this study, day-to-day distances moved by adult females were least during
the summer months (June-August) when the females had young kittens. Late
spring to early summer reduction in female movements and/or home range
size also has been reported by other workers (Bailey 1972, 1979, Berg 1979,
Griffith and Fendley 1986, Kitchings and Story 1979, Lembeck 1978). As noted
above, reduction in daily movements of females with young litters does not
necessarily reflect a decrease in home range size as some workers have
concluded. Intensive monitoring of females with small young in this study
showed that they continued to use their entire home range but in such a way as
to reduce the chances of their being detected in peripheral areas.
More extensive daily movements of both males and females from
December to February were correlated with the main period of juvenile
dispersal. Both breeding season activities and the mobility of older offspring
probably influenced the movements of the females. Kitchings and Story (1979)
reported that adult male bobcats moved longer distances in winter, with no
apparent changes in home range sizes. In contrast, Bailey (1972) found that
adult bobcats of both sexes moved least in fall and winter in Idaho. Among the
possible causes of the apparently different trends in extent of movement in
winter in southeastern and northwestern bobcat populations may be the more
severe winter weather in the latter region, which may cause bobcats to restrict
their movements to certain areas.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
Activity
Diel activity patterns of adult and juvenile bobcats based on 4966 locations
classified as active or inactive are shown in Figure 9. Sample sizes for adult
males, adult females, and juveniles were 1716, 2859, and 391, respectively.
Records of juvenile activity were not obtained during summer months or for
the time period 0300-0600 hours in other seasons. However, for the combined
data, each sex and age group had about the same proportion of observations
for each time interval.
Bobcats were primarily crepuscular and nocturnal in their activity but also
were occasionally active during the daylight hours. Greatest activity occurred
between 1800 and 2400 hours and least activity between 1200 and 1500 hours,
with 91% of the locations during the first interval representing moving
individuals compared with 17% during the second. There was some suggestion
of reduction in activity between midnight and 0300 hours (68% of fixes active)
followed by a slight increase from 0300 to 0900 hours (78% of fixes active).
There were no marked differences in the activity patterns of adult males, adult
females, and juveniles based on the combined data for all seasons.
In summer, males tended to rest more during the daylight hours than in
other seasons (Fig. 10). The higher frequency of inactive locations between
0900 and 1500 hours during summer (June-August) compared with other
seasons was significant (X2 = 30.44, 3 df, p < 0.01). Females (Fig. 11) were
less active from 0300 to 0900 during the period March-May and from 0900 to
1500 hours in the interval from June to August than during the corresponding
times in other seasons (0300-0900: X2 = 4.26, p < 0.05; 0900-1500: X2 = 25.68, 3
df, p < 0.01). However, the reduction of midday activity of females in summer
was less pronounced than that of males.
The overall activity pattern of bobcats in south-central Florida agrees
closely with that observed in northeast Florida by Progulske (1982). Data from
other regions of southeastern United States also indicate that activity is mainly
crepuscular and nocturnal but may also occur during the day. Hall (1973)
reported peaks of movements in summer from 1500 to 2300 hours and from
0300 to 0700. Buie et al. (1979) found peaks in activity in fall, winter, and
spring to occur from 0400 to 1000 and from 1800 to 2400. Miller (1980)
reported least activity from 0700 to 1500 with a second, less pronounced, rest
period from 2200 to 0200.
The reduced daytime activity of adult males during June through August in
this study probably reflects a response to high day-time summer temperatures.
Day-time rest sites were usually in dense closed-canopy habitats, which were
about 3-5C cooler in summer than open canopy areas. In South Carolina,
Buie et al. (1979) also noted that activity was less bimodal during winter than
in early spring and in fall, suggesting greater activity during winter
100-
8 0 -. .
w .Cj..- \ /
60-
- ---Adult males >
20- V
-----Adult females
*-.-Juveniles 8
0- 0
2400 0300 0600 0900 1200 1500 1800 2100
0300 0600 0900 1200 1500 1800 2100 2400
TIME INTERVAL
Figure 9. Activity patterns of adult and juvenile bobcats based on combined data for all seasons from April 1979 to December 1981.
1 1% f
I
-- Jumi- uy
--- Sep-Nov
2400 0300
0300 0600
0600
0900
0900
1200
1200 1500
1500 1800
I I
1800 2100
2100 2400
TIME INTERVAL
Figure 10. Activity patterns of six adult male bobcats during different seasons from April 1979 to December 1981.
lC,
LU
.I-
w
0
w
0~
80-
40- \ /
\ Dec-Fel
20- Adult males ....... -Ma
-A
b
y
,*
Adult fem
100-
80-
----Sep-Nov
2400
0300
0300
0600
0600
0900
0900
1200
1200
1500
I
1500
1800
1800
2100
2100
2400
TIME INTERVAL
Figure 11. Activity patterns of seven adult female bobcats during different seasons from April 1979 to December 1981.
/ *
\ '\ .
'- .\ /\
*\ ""*\ .-/
'"/ *--' Dec-Fe
ales \. ./...... Mar-Ma
--.- Jun-Au.
60-
40-
20-
b
y
I
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
daylight hours when it was warmer. Bailey (1972) stated that bobcats in Idaho
were inactive under conditions of extreme winter weather and that the use of
caves was important in water conservation during hot-dry summer months.
Seasonal differences in activity patterns of adult females in south-central
Florida appeared to be linked more to the needs of their offspring than to
weather conditions. Females with recently born young spent much time with
the young, resulting in a decrease in activity in late-night and early-morning
hours during the first month following birth of litters in spring. In summer,
when young were past the nursing age, females tended to be more active
during daylight hours than were males. This difference in activity levels may
reflect more intense hunting effort required by the increased nutritional needs
of the family unit. The changes in adult female activity pattern correlated with
age of the young were clearly illustrated by the data for Fl, whose activity was
closely monitored from the birth of one of her litters in spring, until summer
when the young were 5 months old (Fig. 12). Even though she was
occasionally fed, this female usually became very thin when her kittens were 3-
7 months of age, supporting the suggestion that energy demands of older young
may force females to hunt more during the day. Hall (1973) also reported
higher levels of activity for females than for males during daylight hours of
summer months.
Habitat Use
Home ranges of all bobcats except two adult females (F10, Fll) included
each of the eight habitat types recognized (Table 6). Closed canopy xeric
pine-oak habitat was not present in the ranges of F10 and Fll, and one of them
(Fll) also had no man-occupied areas within her range. Xeric pine-oak
association was the best represented natural habitat in bobcat home ranges.
The average proportion of the closed canopy phase contained within individual
ranges was double its relative abundance on the study area as a whole.
Although most habitats were found in all home ranges, their proportions in
different ranges were highly variable. In general, the relative amounts of a
given habitat contained in home ranges varied less among adult males than
among adult females. Adult male ranges also tended to contain more
man-modified habitats than did the ranges of adult females, although the
difference was not significant (U57 = 8,p > 0.05, 2-tailed).
Most bobcats did not use habitats in their ranges in direct proportion to
their availability (Table 7). There were no consistent trends in intensity of use
of particular habitats. However, there was an overall tendency for relatively
more use of natural than man-modified habitats. Although adult males had
relatively less natural habitat area within their home ranges than did females,
100-
80- \ -
60 \
W 40- /
WU o
20- Month postpartum
--0-1 r
---4-5 0
0 I I I I I I
2400 0300 0600 0900 1200 1500 1800 2100
0300 0600 0900 1200 1500 1800 2100 2400
TIME INTERVAL
Figure 12. Activity patterns of an adult female bobcat (Fl) during the Ist, 4th, and 5th months after birth of a litter.
Table 6. Percentage distribution of habitat types within overall home ranges of adults and juveniles (observed area of movements within mother's
range). Habitat abbreviations as follows: XO = xeric pine-oak, open canopy; XC = xeric pine-oak, closed canopy; FW = flatwoods; BH =
bayhead; CN = citrus grove or tree nursery; IP = improved pasture; OF = old field; MO = man-occupied. Percentages of each habitat type in
the area of all ranges combined are given below habitat headings in parentheses.
Natural Man-modified
Number of XO XC FW BH Total CN IP OF MO Total
Individual Locations (28) (4) (21) (7) (60) (16) (12) (10) (2) (40)
ADULT MALES
M1 358 29 13 23 4 69 8 12 8 2 30
M2 150 30 5 18 14 67 19 6 6 3 34
M3 116 25 14 6 6 51 40 1 7 2 50
M6 422 27 13 7 3 50 38 3 7 3 51
M8 367 23 2 29 7 61 1 28 11 0.2 40
Mean 283 27 9 17 7 60 21 10 8 2 41
ADULT FEMALES
F1 581 34 4 27 3 68 2 16 14 0.3 32
F3 167 14 44 10 1 69 22 1 2 7 32
F4 518 32 2 23 12 69 17 6 6 2 31
F8 430 22 28 10 5 65 25 1 6 3 35
F9 403 45 1 23 1 70 11 11 6 3 31
F10 34 34 0 27 12 73 2 12 11 2 27
F11 154 13 0 35 17 65 6 4 25 0 35
Mean 327 28 11 22 7 68 12 7 10 2 32
JUVENILES
M4 163 38 5 34 4 81 3 13 4 1 21
M5 19 12 63 7 1 83 10 0.2 5 3 18
F5 51 38 4 36 5 83 1 12 4 1 18
F6 100 37 3 36 4 80 1 14 5 1 21
Mean 83 31 19 28 41 81 2 9 5 2 19
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
they averaged more intensive use of it. Both sexes tended to use open canopy
xeric pine-oak habitats less frequently than other natural habitats. Among
man-modified habitats, adult males used improved pastures more heavily than
did females, but the difference was not significant (U5,7 = 7,p > 0.05, 2-tailed).
Most of such utilization involved crossing pastures at night when traveling
between areas of natural vegetation.
With the exception of semi-tame female F1 who was frequently located in
the vicinity of the dwelling where she was fed, females were associated with
man-occupied habitats less than males. Juveniles showed more intensive use of
certain habitat types than did adults. For example, only one adult (M6) had a
ratio over three for use of any habitat, whereas four out of the five juveniles
had one or more ratios of habitat use ranging from 3.04 to 12.65. Two (M4,
F5) of the four juveniles showed unusually intense association with
man-occupied habitats. These were kittens of the semi-tame female, and their
high use of the man-occupied category reflects visitations of the family group to
the dwelling until the kittens were about 8 months of age. Although F6 was
also a member of this litter, her relatively lower association with man-modified
habitats is explained by the fact that she was the last of the three siblings
captured and thus a greater proportion of the data on her movements was
obtained when the young were older and less frequently accompanied the
mother to the dwelling.
Progulske (1982) presented data on habitat utilization by several bobcats in
northeastern Florida. In his study area, habitats with medium to dense
understories were utilized more than habitats with open understories, and
bottomland hardwoods were the most preferred vegetation association.
Bobcats tended to avoid meadows and other open man-modified habitats but
not pine plantations, which comprised a small fraction (8%) of the study area.
All known den sites of females with young in this study were in natural
vegetation associations, usually thick patches of saw palmetto and dense shrub
thickets. Winegarner (1985b) also recorded 1-month-old young going in and
out of a gopher tortoise (Gophents polyphemus) burrow. Adults without young
also preferred dense palmettos or shrubs for rest sites. In Louisiana, Hall
(1973) also found a preference for heavy cover as rest sites. In the present
study, offspring of females other than F1 apparently were not exposed to
man-modified habitats until about 2 months of age, when they began following
the mother to different rest areas within her range.
Although radiotracking alone was seldom accurate enough to delineate the
exact travel routes of individuals being monitored, a combination of
radiotracking, tracking on foot, the placement of scats and scrapes, and
occasional visual observations indicated that bobcats generally moved about
their home ranges along firelanes, roads, footpaths, animal trails, or railroad
tracks or followed natural openings through the vegetation rather than
bushwacking through dense cover. For example, within the home range of
Table 7. Ratios of proportions of locations in various habitat types to the proportions of the respective habitats in overall home ranges of individual
bobcats. Abbreviations of habitat types as in Table 5.
Natural Man-modified
Individual XO XC FW BH Total CN IP OF MO Total
ADULT MALES
Ml** 1.18 0.85 1.34 1.28 1.18 0.12 0.84 0.60 1.16 0.60
M2** 1.07 0.59 1.17 1.06 1.06 0.55 1.21 1.17 1.72 0.88
M3** 0.73 1.80 1.51 1.99 1.28 0.53 5.46 0.87 2.52 0.73
M6** 0.58 2.90 1.62 1.42 1.39 0.49 1.56 0.69 1.25 0.62
M8** 1.38 2.80 1.16 1.03 1.27 0.19 0.47 0.80 5.58 0.59
Mean 0.99 1.79 1.36 1.36 1.23 0.38 1.98 0.83 2.45 0.68
ADULT FEMALES
Fl** 0.99 2.76 1.20 1.63 1.22 0.33 0.30 0.50 13.23 0.52
F3** 0.50 1.66 0.33 0.31 1.22 0.52 0.09 0.67 0.54 0.54
F4** 0.90 0.76 0.90 1.88 1.06 0.78 0.60 0.85 2.27 0.86
F8** 0.68 1.81 1.10 1.36 1.29 0.28 2.31 0.39 1.27 0.47
F9** 1.26 0.98 1.22 1.24 1.24 0.31 0.57 0.67 0.18 0.46
F10 0.80 1.08 0.61 0.88 1.08 0.62 2.23 0.02 1.34
F11** 0.42 0.95 0.71 0.78 0.76 0.55 1.73 1.42
Mean 0.79 1.59 0.97 1.11 1.10 0.58 0.71 1.01 2.92 0.80
JUVENILES
M4* 0.85 3.61 1.05 0.52 1.07 0.12 0.33 0.45 12.65 0.69
M5 1.24 0.95 0.80 0.01 0.95 0.93 0.01 2.07 1.01 1.25
F5* 0.98 2.47 0.94 0.75 1.02 0.01 0.61 9.44 10.89 0.91
F6** 0.65 2.86 0.99 3.04 1.01 0.02 0.66 0.85 2.86 0.92
Mean 0.93 2.71 0.95 1.08 1.01 0.27 0.40 3.20 6.85 0.94
* Differences in observed and expected frequencies of locations significant at P < 0.05 level on basis of G-statistic
** Differences in observed and expected frequencies of locations significant at P < 0.01 level on basis of G-statistic
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY
adult female F9 quadrats containing segments of roads, trails, railroad tracks,
or paths (n = 345) comprised 64% of the total of 540 quadrats but contained
83% of active fixes (X2 = 39.58, 1 df, p < 0.01). The cats also hunted along
open travel ways, but usually carried prey into dense cover to consume it.
Other studies in the southeastern United States indicated a similar predilection
of bobcats for use of roads, paths, and other routes when traveling (Hall 1973;
Miller 1980).
Marking Behavior
Frequency of Types of Marking Behavior.- Scrapes were the most
frequent type of marking observed. Of 863 fresh scrapes recorded, 42% (363)
contained feces, 57% (488) contained urine, and 1% (12) were empty. Scrapes
were made by both adults and older juveniles. Young (a male and female) of
the semi-tame female began making fecal scrapes when about 5 months old, at
which age they began to accompany the mother to the periphery of her range.
Prior to that age the young and mother tended to bury their feces in common
sites in the vicinity of rest areas. Deposits of buried feces were also found in
the vicinity of a rest site of another female (F9) with small kittens. Urine
marking was done by both adults and juveniles. Among adults, both sexes
were observed spray-urinating, but only females were observed squat-urinating
without first scraping. A juvenile of unknown sex about 5-6 months old also
was recorded squat-urinating without scraping. Fecal marking by adults and
juveniles was frequent. Deposition sites were usually on paths, bare patches of
ground, or mounds where the feces were conspicuous. Sometimes large
numbers of feces accumulated at a particular site.
Scratching posts, trees or other places used by bobcats for sharpening their
claws, also may have communicatory as well as maintenance functions. Only
two scratching posts were encountered in the study area. Both were dead
stubs. One of these was regularly used by the semi-tame female near the
cottage at which she was fed.
Seasonal and Yearly Variation in Marking.- Counts of exposed scats in
February, March, July, and August 1979 showed pronounced seasonal
variation, ranging from 1.1 to 2.5 scats/km in February to 0.1-0.5/km in July
and August. Similar seasonal trends occurred in the incidence of the three
types of marking (Fig. 13). The peak of marking activity in this study coincided
with the peak in breeding and period of high mobility of older juveniles, while
reduced incidence of marking occurred during the period of late gestation and
presence of young litters.
6 -
6 Urine scrapes
----Scats in scrapes
5- ............Scats not in scrapes
4-
2 /
1980 1981 \
Figure 13. Monthly frequencies of three types of bobcat marking from January 1980 to March 1981.
Z \ / z
1\ .>
0 -............... ... I
J F M A M J J A S O N D J F M 0
1980 1981 r
Figure 13. Monthly frequencies of three types of bobcat marking from January 1980 to March 1981. 3
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 219
The data suggest the following trends in marking behavior related to the
reproductive cycle of the adult female: (1) Resident adult females with nursing
kittens tend to bury their feces in the vicinity of the den site or elsewhere in
their range but continue spray- and squat-urinating within the interior of their
ranges and along range boundaries. Young kittens probably also bury feces
near the dens. (2) Females and mobile juveniles 4-7 months old bury feces at
common, frequently-used sites near rest areas within the female's home range
and squat- and spray-urinate along travel routes. (3) At about 5-6 months of
age, juveniles begin leaving feces exposed in scrapes and probably begin to
urine-scrape as well as squat- and spray-urinate. (4) As juveniles continue to
move about the mother's range and along its boundaries, they increasingly
leave more feces exposed and make more urine and fecal scrapes. (5) About
the time juveniles are ready to disperse (which often coincides with the
breeding season of the mother), they are marking at their highest rate, as are
adults. (6) After breeding and the dispersal of their young, resident adult
females gradually decrease their rate of leaving feces exposed and increase
their rate of burying scats so that by the time new litters are born fecal marking
is minimal. (7) Intensity of adult male marking behavior parallels that of adult
females and may be at least partly a response to the marking activities of the
female and young.
The patterns of marking behavior of Florida females and young generally
parallel those observed by Bailey (1972, 1979) in Idaho. Ontogenetic changes
in marking behavior of the lynx are apparently generally similar to those in
bobcats. Lindemann (1955) reported that European lynxes began to return to
depositories to bury urine or feces at 100-120 days of age and initiated marking
of ranges with exposed excrement at ages of 210-220 days. Saunders (1961)
also noted that juveniles in North America switched from burying feces to
leaving them exposed as they grew older and thus began marking like adults.
Few comparative data are available on seasonality of marking behavior in
other bobcat populations, and quantitative information is limited to frequency
of scat deposits. In northeastern Florida, Conner (1982) recorded greatest
frequency of scats along roads, trails, and firelanes during winter and spring
and the lowest incidence in summer and fall. In Virginia, 57% of scats
observed along trails over a 1-year period occurred from mid-September
through mid-March and 43% during the balance of the year (Progulske 1952).
Frequencies of scats on Louisiana study sites were higher in winter and spring
and lower in summer and fall (Hall 1973). Miller (1980) stated that scat
deposition by bobcats in Alabama was more frequent in winter and early spring
and less obvious in other parts of the year. In contrast to this and other
southeastern studies, no seasonal pattern was evident in monthly scat
collections made by Kight (1962) in South Carolina. Scat deposition in
southwestern populations also showed seasonal variation. Percentages of scats
recorded by Jones (1977) in Arizona in different months from October through
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
March were 38% in October and November, 7% in December and January,
and 55% in February and March. He suggested that the differences were due
to weather (which might account for the overall lower trend in early winter),
changing activity patterns of bobcats, and possible seasonal differences in
bobcat behavior. As in the present study, the peak frequency of scat deposition
in late-winter was correlated with the period of mating. In another Arizona
study, Small (1971) reported monthly frequencies of scats/km of 0.04 in
March and April, 0.58 in May, 0.18 in June, and 0.12 in July.
The data, particularly counts of urine scrapes, suggested a higher incidence
of marking activity in fall-winter 1980-1981 than the previous year. Frequency
of exposed scats with and without scrapes on the 10 km census line in February
was higher in 1979 (5.5/km) than in 1980 (2.8) or 1981 (2.7). The higher level
of marking, particularly urine scrapes, in late fall and winter of 1980-81
compared with 1979-80 might have reflected the slightly higher adult male
density in the second year, although estimated numbers of adult females and
juveniles were higher in 1979-80. The lower level of marking in 1979-80 also
might have resulted from the greater instability of home ranges that year than
in 1980-81 caused by the deaths from feline panleucopenia.
Spatial Patterns of Marking Behavior.- The distribution of marking sites
in a part of the study area that contained portions of the home ranges of two
adult males and three adult females with mobile young during October-
December 1979 (Fig. 14) provided detailed evidence on the relationship of
marking behavior to social organization of the population. Marking clearly was
concentrated along home range boundaries. Of 273 4-ha quadrats that
contained segments of scat and scrape census routes, 60 also contained
segments of home range boundaries while the remaining 213 were in the
interior portions of home ranges. Quadrats with home range boundaries had a
significantly higher frequency of marking than those within home ranges (85%
vs. 31%, X2 = 54.38, 1 df, p < 0.001). There was a greater tendency for urine
scrapes than for fecal scrapes to be located at home range boundaries.
Quadrats including home range boundaries contained 88% of 248 urine or
presumed urine scrapes compared with 65% of the 265 fecal scrapes or
exposed scats. Similar relationships between home range boundaries and
marking sites were found in other seasons. For example, the same area was
thoroughly searched for scats and scrapes in July 1980, and 22 exposed scats
and 55 known or presumed urine scrapes estimated to be not over 2 months
old were recorded; 14 (64%) of the scats and 50 (91%) of the urine scrapes
were in quadrats containing home range boundaries. Four of the five
remaining urine scrapes were located near two rest sites used by two females
with non-mobile kittens. In fall and winter 1980-81, there was a shift in the
focus of marking activity in this part of the study area which correlated with a
shift in home range boundaries.
WASSMER ET AL.: SOUTII-CENTRAL FLORIDA BOBCAT ECOLOGY
M31 M1l
/
a
S
* 0 01
000
0
0
0
A A 0
*
00
L,-----.-- F3
--------M3
ONIM/m
* 0
A
0%.
0 1 -..
km / -\
Urine Scats
A 1-5 1-5 ,
A 6-10 *6-10
A11+ 011+
X//Quadrats not sampled
Figure 14. Distribution of scats and urine scrapes in 4-ha quadrats in relation to home range
boundaries of two adult males (Ml, M3) and three adult females (Fl, F3, F4) during the period
23 October-19 December 1979 in a part of the study area represented by the stippled area on the
inset map.
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
The distribution of various types of marks within bobcat home ranges
supports the usual conclusion from home range configuration and other
evidence that bobcats are territorial. Krebs and Davies (1978) recognized any
occupied area as a "territory" whenever individuals or groups are spaced out
more than would be expected from a random occupation of suitable habitats
and when this spacing is due to interactions between these individuals or
groups. By this definition, bobcat home ranges can be considered intra-sexual
territories. Gorman (1980) noted that among mammalian carnivores
non-territorial species mark throughout their home range, whereas territorial
species mark more intensively at the borders of their ranges. He suggests that
animals mark their range in order to orient themselves and that boundary
marking is a specialized form of range marking, serving either to inform the
animal doing the marking that it is at the edge of its territory or to warn and
repel conspecifics. Marking also may have other functions, including
providing information on an individual's identity, age, sex, reproductive state,
or social status (see Leyhausen 1979, MacDonald 1980, Wemmer and Scow
1977 for further discussion).
Evidence of bobcats using marking to advertise the home range boundary
was first presented by Marshall (1969). Bailey (1972) and McCord (in McCord
and Cardoza 1982) provided further substantiation of this function of marking.
Our observations on Florida bobcats add additional support to the hypothesis
that one of the functions of marking is to inhibit bobcats from trespassing on
another individual's home range. Bobcats deposited exposed feces and made
fecal and urine scrapes more frequently at the periphery of the home range
than in the interior, which suggests that this type of marking behavior was
related to the maintenance of range boundaries. In addition, as home range
boundaries shifted, there was a corresponding shift in the locus of marking,
and bobcats regularly visited sites on their range boundaries and "refreshed"
older marks with new ones. Type of deposit at a site was not necessarily
consistent, as bobcats would often alternate between fecal-scraping and
urine-scraping at the same location. Adjacent pairs regularly visited these sites
and added their own deposits to them. Generally, feces tended to begin
deteriorating after about a week, especially during the rainy season and when
scarab beetles were active. Urine odor was strongest the first few days after
the deposit. These observations suggest a need for bobcats to regularly renew
levels of whatever substances might be used in advertising their status, and that
neighboring individuals periodically inspected sites for information concerning
other depositors. In this regard, it may be significant that bobcats were not
known to invade the vacated ranges of same-sexed bobcats immediately after
their death. Rather, 5-14 days elapsed before invaders were detected within
the vacated ranges. The observed time-lag before invasion was about the same
as the time taken for feces to deteriorate and for urine odors to diminish. In
the case of adult female F3 who abandoned her home range to her daughter
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 223
(F8), the daughter had been marking at the mother's home range boundary
prior to the adult's disappearance, and there were no apparent attempts by
neighboring adult females to invade the range. This suggests that continued
marking along the boundary, even by a different individual, served to maintain
the integrity of the range.
CONSERVATION AND MANAGEMENT IMPLICATIONS
Several findings of this study appear relevant to conservation and
management of bobcat populations. Our data indicate that even when not
subject to significant direct exploitation by trapping or hunting, Florida bobcat
populations may experience high mortality from natural and man-related
causes. If, as found for the Canada lynx (Brand and Keith 1979), hunting and
trapping mortality in bobcat populations is additive rather than compensatory,
the mortality rate may be very high even in relatively lightly harvested
populations. The importance of adult mortality in the population dynamics of
bobcats was demonstrated by simulations based on data from Mississippi,
indicating that a given percentage change in annual adult mortality has about
twice the effect on population size as a similar change in litter size or kitten
survival (Gluesing et al. 1987).
Most of the known litters were produced in the core area and females with
young litters concentrated their activity there. General observations indicated
that food resources also were better in the core than in the remainder of the
study area, and all cases of man-related mortality occurred in the surrounding
semi-developed area. This illustrates the important role of large tracts of
protected habitat in developed areas in maintaining regional populations of
bobcats and other large, mobile vertebrates. In landscapes characterized by
interspersed natural and developed areas, the former probably serve as the
primary source of new individuals and the latter as population sinks.
Death of resident individuals had a marked effect on the spatial
relationships of surviving bobcats of the same sex. This is a factor that
deserves consideration in assessing the potential impact of harvesting on a
population. The disruption of the social organization of the population
resulting from increased removal of individuals may lead to reduced
productivity and an increase in mortality from other causes. Hornocker and
Bailey (1986) also stressed the potential effect of man-caused mortality in fetid
populations in "creating behavioral instability and keeping the social
organization in a perpetual state of flux."
In this study disease was a major cause of mortality and may play a more
important role in bobcat population dynamics than previously suspected.
Without relatively intensive and long-term monitoring of an adequate number
BULLETIN FLORIDA STATE MUSEUM VOL. 33(4)
of radio-equipped animals, the occurrence of disease-related mortality in
bobcats is unlikely to be detected. The role of domestic cats and other wildlife
species, such as raccoons, as reservoirs and vectors of parasites and diseases of
bobcats is an additional factor that needs to be considered in bobcat
management. As more development encroaches upon Florida bobcat habitats,
feral cats may become increasingly important as a source of FPLV outbreaks.
The occurrence of feline panleucopenia in Florida bobcat populations may also
pose a threat to the endangered Florida panther (Felis concolor coryi).
Bobcats are common in areas of the confirmed remaining panther populations
and could be a reservoir for feline panleucopenia, increasing the probability of
the disease spreading to panthers. Roelke et al. (1984) reported FPLV
antibodies in 8 of 13 bobcats and 9 of 10 panthers examined from areas of
south Florida where the two species coexist.
Home range estimates for females based on daytime or infrequent radio
fixes and density estimates derived from such data should take into account the
seasonal variation in the pattern and timing of movements related to the
reproductive status of the female. This study indicated that females with
non-mobile young not only exhibit a temporal shift in activity but reduce the
time spent at the periphery of their home range. Failure to monitor their
movements intensively enough to compensate for the decreased probability of
detecting them at the true limits of their home range could result in
underestimation of home range size and overestimation of density.
The marked seasonal trends in marking behavior and tendency to mark
more frequently at range boundaries have important implications with regard
to census techniques that use counts of scats as an index of abundance.
Censuses should be conducted at the same time of year, probably during late
fall-early winter when marking is at its peak. Concentration of scent-marking
along range boundaries could lead to erroneous interpretations of abundance if
some census routes happen to be located along range boundaries, which often
coincide with roads or trails, whereas others are not. These considerations
may also apply to scent-post census techniques, because the responsiveness of
a bobcat to a scent post is probably related to marking behavior and thus may
vary both seasonally and in relation to the location of the scent post station
within its home range.
WASSMER ET AL.: SOUTH-CENTRAL FLORIDA BOBCAT ECOLOGY 225
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