Spatial Organization of Adult Bobcats in a Longleaf Pine-Wiregrass Ecosystem in Southwestern Georgia
Jessica C. Cochrane, Jordona D. Kirby, Ivy G. Jones, L. Mike Conner, and Robert J. Warren
Southeastern Naturalist, Volume 5, Number 4 (2006): 711–724
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2006 SOUTHEASTERN NATURALIST 5(4):711–724
Spatial Organization of Adult Bobcats in a Longleaf
Pine-Wiregrass Ecosystem in Southwestern Georgia
Jessica C. Cochrane1,*, Jordona D. Kirby1, Ivy G. Jones1, L. Mike Conner1,
and Robert J. Warren2
Abstract - Lynx rufus (bobcat) home-range sizes have been studied throughout the
Southeast, but study duration is generally 2 years and number of bobcats sampled is
often < 20. There have been even fewer studies dealing with spatial interactions of
bobcats, and fewer still within a Pinus palustris (longleaf pine) ecosystem. Because
both bobcat home-range sizes and the degree that space is shared by bobcats are highly
variable, it is important to understand factors that influence bobcat home-range size and
spatial organization within the various habitats where this species is found. Therefore,
we determined seasonal and annual home-range sizes and spatial overlap of bobcats in a
longleaf pine forest in southwestern Georgia. We monitored 44 radio-collared bobcats
(17 M and 27F) during 2001–2004. Gender and year did not interact to affect bobcat
annual home-range sizes (95% adaptive kernel), and annual differences in annual homerange
sizes were insignificant. However, male bobcats had annual home-range sizes
almost 2 times greater than those of females. Gender and season interacted to affect
seasonal home-range sizes of bobcats; thus, we analyzed seasonal home-range sizes for
each gender separately. Seasonal home-range sizes of male bobcats did not differ.
However, for female bobcats, the greatest home-range sizes occurred during winter of
2003 and the smallest during summer of 2002. We examined 3 types of spatial overlap:
male-male, female-female, and female-male. Home-range overlap differed among
types; female-male overlap was approximately 1.6 times greater than female-female
overlap and approximately 2.8 times greater than male-male overlap. Our home-range
sizes were among the smallest reported in the Southeast. While intrasexual overlap is
generally considered rare in bobcats, we observed sharing of space by male-male and
female-female pairs. Furthermore, space shared by female-female pairs exceeded that
of male-male pairs, contrary to hypotheses concerning land tenure of solitary carnivores.
Land-management practices, such as prescribed burning and maintenance of
food plots, provided abundant small prey for bobcats and best explain smaller homerange
sizes of bobcats in this study relative to that reported in most other southeastern
studies. We suggest that spatial exclusivity among male-male and female-female pairs
is most likely when prey are moderately abundant, but that exclusivity of home ranges
may be abandoned when prey are either abundant or rare. Further investigation into
home-range overlap is needed to consider the effect of bobcat density on these variables.
Lynx rufus Schreber (bobcat) is a solitary carnivore with home-range
sizes apparently influenced by geographic region (Anderson 1987, Berg
1979), gender (Hall and Newsome 1976, Kitchings and Story 1979), season
1Joseph W. Jones Ecological Research Center, Route 2, Box 2324, Newton, GA
39870. 2Daniel B. Warnell School of Forest Resources, University of Georgia,
Athens, GA 30606. *Corresponding author - firstname.lastname@example.org.
712 Southeastern Naturalist Vol. 5, No. 4
(Anderson 1987, Sandell 1989), habitat quality (Rucker et al. 1989), prey
availability and abundance (Fendley and Buie 1986), and time-in-residence
(Conner et al. 1999). Home ranges of bobcats in the Southeast vary from 1.1
km2 for females and 2.6 km2 for males (Miller and Speake 1979) to 24.5 km2
for females and 64.2 km2 for males (Rucker et al. 1989).
Male home ranges typically exceed those of females by 2–3 times, and
may be as much as 5 times greater (Buie et al. 1979, Hall and Newsom 1976,
Kitchings and Story 1979, Whitaker et al. 1987). Male home-range size is
thought to be affected by size of female home ranges and number of mating
opportunities; whereas, female home ranges appear to be regulated by diversity,
abundance, stability, and distribution of prey populations (Anderson
1987, Sandell 1989). Differences in habitat quality often are used to explain
home-range variability in L. rufus (Anderson 1987). According to the bobcat
habitat suitability index model, suitability of habitat is determined by the
ability of an area to support prey populations (Boyle and Fendley 1987).
Studies have documented an inverse relationship between prey abundance
and home-range size (Buie et al. 1979, Knick 1990). Habitats more suitable
for abundant prey densities are more likely to be included in a bobcat’s home
range, and greater quality habitat should result in smaller home ranges (Buie
et al. 1979, Knick 1990). Conner et al. (2001) suggested that habitat quality
influences bobcat home-range size, but once habitat quality increases to a
threshold, home ranges become influenced by other factors such as bobcat
density and breeding opportunities.
Although few studies of bobcats in the Southeast have addressed seasonal
variation in home-range size, existing studies throughout the United
States suggest that males have greater home ranges during the breeding
season, and females have smallest home ranges during parturition and kitten-
rearing (Anderson 1987, Conner et al. 1992, Knick 1990). Seasonal
fluctuation in home-range sizes also may relate to seasonal differences in
prey availability. Home ranges were smallest during summer in Arkansas,
probably because prey abundance was greatest during the warmest months
(Rucker et al. 1989). In South Carolina, bobcat home-range size did not vary
seasonally (Fendley and Buie 1986).
Male bobcat home ranges typically overlap several female home ranges
and those of other males (Anderson 1987, Bailey 1974, Buie et al. 1979, Hall
and Newsom 1976, Miller and Speake 1978, Nielsen and Woolf 2001,
Whitaker et al. 1987). Intersexual overlap typically is greater than
intrasexual overlap, and female home ranges typically are exclusive of other
females (Anderson 1987, Buie et al. 1979, Hall and Newsom 1976, Marshall
and Jenkins 1966, McCord and Cordoza 1982, Miller and Speake 1979,
Whitaker et al. 1987). However, some studies reported frequent overlap
among female home ranges, ranging from 21% (Chamberlain and Leopold
2001) to 36% in California (Zezulak and Schwab 1979). Kitchings and Story
(1984) observed 2 adult females with kittens using the same area, and studies
have documented extensive evidence of sub-adults and transients being
2006 J.C. Cochrane, J.D. Kirby, I.G. Jones, L.M. Conner, and R.J. Warren 713
tolerated within adult home ranges (McCord 1974, Miller and Speake 1979,
Provost et al. 1973). In some cases, male exclusivity also was observed
(Zezulak and Schwab 1979).
Spatial organization in bobcats may be influenced by climate, habitat,
population density, and prey abundance (Anderson and Lovallo 2003). In
2 studies of bobcats in South Carolina, bobcats had greater home ranges
and less intrasexual overlap 12 years after the initial study had occurred
(Buie et al. 1979, Marshall and Jenkins 1966), presumably the result of
altered land use and decreased prey abundance. Increased bobcat densities
and smaller home ranges were associated with exclusive home ranges
for both genders (Lembeck and Gould 1979, Miller and Speake 1979).
Bailey (1981) suggested that female home ranges should be small and
exclusive in warm climates where resources are abundant. Male home
ranges also should be small in warm climates with minimum overlap from
other males (Anderson 1987, Bailey 1981). Another potential factor influencing
home-range overlap is genetic relatedness, but spatial and genetic
relatedness in bobcats have not been extensively investigated (Chamberlain
and Leopold 2001). Because there are relatively few studies of bobcat
spatial organization with > 2 year duration, particularly within a Pinus
palustris P. Mill (longleaf pine) ecosystem, our objectives in this study
were to determine annual and seasonal home-range sizes of bobcats in a
longleaf pine ecosystem in southwestern Georgia, and to determine the
extent that bobcats shared space with neighboring individuals.
We conducted the study on Ichauway, which is a privately-owned,
11,735-ha research facility located in Baker County, GA, 16 km south of
Newton, GA. It is located in the Dougherty Plain physiographic province in
the southeastern Gulf Coastal Plain. Approximately 24 km of the
Ichawaynochaway Creek flows through the study area, and the Flint River
forms almost 22 km of Ichauway’s eastern boundary. Ichauway is characterized
by flat to gently rolling karst topography, with elevations ranging from
27 to 61 m. It has hot, humid summers and short, mild, wet winters, with
average daily temperatures ranging from 11 ºC (winter) to 27 ºC (summer)
and an average annual precipitation of 132 cm (Boring 2001).
Longleaf pine woodlands and limesink wetlands are the dominant
habitat types at Ichauway. The longleaf pine understories are dominated
by Aristida stricta Michx.(wiregrass) and old-field grasses (e.g.,
Andropogon spp.), but > 1000 vascular plant species occur on the site
(Drew et al. 1998, Goebel et al. 1997). Other habitats include mixed pinehardwood
areas, food plots, agricultural fields, P. elliottii Engelm (slash
pine) flatwoods, riparian hardwood hammocks, oak (Quercus spp.) sandhill
barrens, natural and old-field P. taeda Linnaeus (loblolly pine)
stands, Taxodium ascendens Brongn. (grassy gum) and Nyssa biflora
Walter (cypress-gum) limesink ponds, creek swamps, forested wetlands,
714 Southeastern Naturalist Vol. 5, No. 4
riverine areas, shrub-scrub upland, and human/cultural (i.e., resident
quarters) areas (Boring 2001).
Much of Ichauway is managed by prescribed fire. Burning is performed
on a 2-year rotation, usually during winter and early spring, on 4000–6000
ha throughout the entire site (Godbois et al. 2004). Prescribed burning is
used to control understory vegetation, reduce hardwoods, manage wildlife
habitat, reduce fuel buildup, promote wiregrass seed production, prepare
sites for pine regeneration, and for experimental research and educational
activities (Boring 2001).
Food plots, consisting of Brachiaria ramose (L.) Stapf (brown top
millet), Triticum aestivum Linnaeus (winter wheat), (Vigna spp. (cowpea),
Sorghum vulgare Persoon (grain sorghum), and Sorghum spp.
(Egyptian wheat) comprise 20% of the property (Godbois et al. 2004).
Fields are disced to improve Colinus virginianus Catesby (Northern Bobwhite)
food availability by allowing Ambrosia artemisiifolia Linnaeus
(ragweed) and Chamaecrista fasciculate Michaux (partridge pea) seedlings
and other plants to grow (Davis 2001, Landers and Mueller 1986).
Supplemental food, comprised of various agricultural grains, is provided
across the property as part of the quail-management activities during
November–May. The open-canopied forest, frequent prescribed fires,
food plots, and supplemental feeding, contribute to a dense prey population
for bobcats (Godbois et al. 2004).
Annually during March–May, limited predator removal occurs in select
quail-management zones on the property. The primary predators removed
are Procyon lotor Linnaeus (raccoons) and Didelphis virginiana Kerr (opossums).
Low numbers of Canis latrans Say (coyote), Vulpes vulpes Linnaeus
(red fox), Urocyon cinereoargentus Schreber (gray fox), and Mephitis mephitis
Schreber (striped skunk) also are removed annually. Bobcats were not
harvested during this study.
Bobcat capture and monitoring
We trapped bobcats using Victor Number 1.75 offset and Number 3
Soft Catch® traps (Woodstream Corp., Lititz, PA). Animals were captured
from December 2000 until May 2004, although trapping efforts
were sporadic between July 2001 and October 2003. Captured animals
were netted and given an intramuscular injection of ketamine hydrochloride
(10 mg/kg body weight) (Seal and Kreeger 1987). We classified
animals as adult or juvenile based on secondary gender characteristics,
length, and weight (Crowe 1975). Adults were fitted with a 180-g VHF
radio-collar (Advanced Telemetry Systems, Isanti, MN). Each bobcat
received a uniquely numbered ear tattoo. Bobcats were monitored and
released 8 to 24 hours after sedation at the trap site to ensure full recovery.
All trapping procedures were approved by the University of Georgia
Institutional Animal Care and Use Committee (IACUC #A990159).
2006 J.C. Cochrane, J.D. Kirby, I.G. Jones, L.M. Conner, and R.J. Warren 715
Using radio telemetry, we began monitoring bobcats 2–7 days after
release. We obtained locations by triangulation, taking 2 azimuths from
known reference points with a 3-element Yagi antenna (Sirtrack, New
Zealand) and hand-held receiver (Wildlife Materials Inc., Carbondale,
IL). To minimize error due to animal movement between readings, time
between consecutive bearings was always < 15 minutes, but rarely exceeded
5 minutes (Cochran 1980, Kenward 1987, White and Garrott
1990). Each bobcat was located 4–6 times weekly, and locations were
obtained equally throughout the diel period, with > 8 hours between each
location to ensure biological independence.
We used the FORTRAN program EPOLY (L.M. Conner, Joseph W. Jones
Ecological Research Center, Newton, GA, pers. comm.) to convert radiotelemetry
locations into Universal Transverse Mercator (UTM) coordinates.
We calculated 95% adaptive kernel (ADK; Worton 1989) annual and seasonal
home ranges for bobcats with 30 locations per calendar season using
CALHOME (Kie et al., 1996). We also calculated 95% minimum convex
polygon (MCP) home-range estimates to compare with other studies and for
overlap analysis (Mohr 1947). However, we did not test hypotheses regarding
home-range size using MCP home ranges as this would have been redundant.
Annual home ranges were determined for animals monitored for 4 consecutive
seasons. When the same animal was tracked for multiple years, we
considered the animal within a year as the experimental unit.
To determine if annual home-range size differed as a function of gender,
year, or a gender x year interaction, we performed an analysis of
variance (ANOVA) using PROC GLM (SAS Institute 2003). We used
PROC MIXED (SAS Institute 2003) and a repeated measures ANOVA to
determine whether seasonal home-range size differed as a function of
gender, season, or their interaction. In the repeated measures ANOVA,
animals were treated as the subject, repeated over seasons. We considered
statistical significance at = 0.10.
To determine spatial overlap of bobcats, we overlaid home ranges for all
individuals to determine the common area shared by pairs of animals. We
then classified overlap by type (i.e., male-male, female-female, male-female).
We calculated percentage area overlap associated with each home
range (common area/home-range area), and calculated percentage point
overlap by extracting all telemetry locations for each bobcat within the
overlap area and dividing this number of locations by the total number of
locations for that animal. We then calculated an index of overlap, which was
the product of the percentage area overlap and the percentage point overlap
for all overlapping bobcats. For example, assume bobcat A and B have
overlapping home ranges. The index of overlap for bobcat A would be the
percentage area overlap A x percentage point overlap A x percentage point
overlap B. Because the index of overlap ranged between 0 and 1, we used an
716 Southeastern Naturalist Vol. 5, No. 4
arcsine square root transformation on index of overlap prior to analysis (Zar
1996). We then used ANOVA to determine if overlap varied by type (i.e.,
MM, FF, or FM), season, and their interaction. We considered statistical
significance at = 0.10.
We radio-tracked 13–27 bobcats seasonally during 21 September 2001–
20 June 2004. We monitored 44 individual animals (17 M and 27 F). Of
these,we monitored 29 bobcats (7 M and 22 F) for 4 consecutive seasons
and used these 29 animals to estimate annual home ranges.
When we analyzed annual ADK home-range sizes, there was no gender x
year interaction (F1,25 = 0.15, P = 0.700). Annual home ranges of male
bobcats (11.0 ± 1.4 km2) were almost 2 times greater (F1,25 = 7.54, P = 0.011)
than those of female bobcats (6.4 ± 1.0 km2), but annual home ranges did not
differ (F1,25 = 2.79, P = 0.107) among years.
Analysis of seasonal home ranges indicated a significant gender x season
interaction (F10,181 = 1.64, P = 0.100); thus, we examined seasonal home
ranges separately for each gender. Seasonal home-range sizes varied (F10,124
= 3.22, P = 0.001) for females, but not for males (F10,51.6 = 0.88, P = 0.554;
Fig. 1). Seasonal home range of male bobcats averaged 8.5 ± 1.0 km2 and
female bobcats averaged 5.3 ± 0.7 km2. The smallest female home ranges
Figure 1. Seasonal home-range sizes for male and female bobcats (F01 = Fall 2001;
W02 = Winter 2002; S02 = Spring 2002; Su02 = Summer 2002; F02 = Fall 2002; W03
= Winter 2003; S03 = Spring 2003; Su03 = Summer 2003; F03 = Fall 2003; W04 =
Winter 2004; S04 = Spring 2004) on Ichauway, Baker County, GA, 2001–2004.
2006 J.C. Cochrane, J.D. Kirby, I.G. Jones, L.M. Conner, and R.J. Warren 717
(2.8 ± 1.7 km2) occurred during summer of 2002, and the largest home
ranges (8.5 ± 1.7 km2) occurred during winter of 2003.
Type of overlap and season did not interact to affect index of overlap
(F20,351=0.63, P=0.8903), and home-range overlap (F10,351 = 0.39, P = 0.952)
did not vary seasonally. However, type of home-range overlap differed
(F2,351 = 8.67, P 0.001). Intersexual home-range overlap (22.6%) was
approximately 1.6 times greater than female-female (13.8%) and 2.8 times
greater than male-male (8.2%) home-range overlap.
Similar to most studies of bobcat home ranges in the southeastern US, we
observed that male bobcats had greater home ranges than females (Table 1).
However, home ranges on our study area were among the smallest home
ranges reported in the region (Buie et al. 1979; Conner et al. 1992, 2001;
Diefenbach et al. 2006; Hamilton 1982; Kitchings and Story 1979; Lancia et
al. 1986; Rucker et al. 1989; Shiftlet 1984). Bobcats in areas with abundant
prey do not have to travel as far while foraging, resulting in decreased homerange
size (Buie et al. 1979, Knick 1990). The size of prey eaten by bobcats
also may explain our smaller home-range sizes; predators that prey on
smaller animals tend to have smaller home ranges (McNab 1963). Sigmodon
hispidus Say and Ord (cotton rats), an approximately 100-g rodent, are the
primary prey species consumed by bobcats on our study site (Godbois et al.
2003). Therefore, bobcats on our study site may hunt shorter distances than
bobcats which prey on larger animals. Because prey abundance (Bailey
Table 1. Studies documenting bobcat annual home-range sizes (km2) in the southeastern
United States (MMA = modified minimum area; MCP = minimum convex polygon; ADK =
Sample Home range Home-range
Reference State size Male Female model
Hall and Newsom 1976A LA 3F, 3M 4.9 1.0 MMA
Kitchings and Story 1979 TN 3F, 2M 42.9 11.5 MCP
Miller and Speake 1979 AL 6F, 6M 2.6 1.1 MCP
Buie et al. 1979B SC 3F, 4M 20.8 10.3 MCP
Hamilton 1982 MO 10F, 20M 60.4 16.1 MCP
Shiftlet 1984 MS 3F, 4M 10.1 5.9 MCP
Fendley and Buie 1986 SC 3F, 4M 3.2 1.6 MCP
Lancia et al. 1986A NC 3F, 5M 37.7 22.1 MCP
Rucker et al. 1989 AR 3F, 5M 64.2 24.5 MCP
Conner et al. 1992 MS 10F, 5M 36.5 20.6 MCP
Griffin 2001 SC 7F, 5M 10.5–16.7 3.5–10.5 ADK
Chamberlain et al. 2003 MS 38F, 20M 20.2 12.3 MCP
Diefenbach et al. 2006 GA 38F, 32M 22.1 13.6 ADK
This study GA 22F, 7M 8.2 5.2 MCP
This study GA 22F, 7M 11.0 6.4 ADK
AUsed only summer data.
BUsed only fall and winter data.
718 Southeastern Naturalist Vol. 5, No. 4
1974, Buie et al. 1979, Sandell 1989) and prey size (McNab 1963) may
partially explain bobcat home-range size, prey abundance and prey size are
perhaps the best explanation for the relatively small bobcat home ranges
observed during our study.
We suggest that management practices conducted on our study area were
responsible for creating relatively abundant prey populations. Management
of our study area included prescribed fire at approximately 2-year return
intervals, with 4000–6000 ha being burned annually. Prescribed fire increases
and maintains a dense herbaceous understory, ultimately providing
habitat capable of supporting abundant bobcat prey (Golley et al. 1965,
Miller and Speake 1979). Approximately 20% of the study area is composed
of wildlife food plots and agriculture (Godbois et al. 2004). Planting agricultural
crops and maintaining quail food plots increases edge, providing ample
resources for prey (Cummings and Vessey 1994, Hall and Newsom 1976,
Miller and Speake 1978). Additionally, approximately 270 metric tons of
grain sorghum are spread for quail over 7020 ha throughout Ichauway
between November and May each year (Godbois et al. 2004). In a preliminary
analysis of small mammal data collected on our study area, cotton rat
populations were 5.5 times greater, Mus musculus Linnaeus (house mouse)
were 3.5 times greater, Peromyscus gossypinus LeConte (cotton mouse)
were 1.5 times greater, and Reithrodontomys humulis Audubon and
Bachman (eastern harvest mouse) were 2 times greater in supplementally fed
versus unfed areas (L.M. Conner, unpubl. data). Doonan and Slade (1995)
also observed an increase in small mammal densities in supplementally fed
areas compared to controls. This concentration of prey may alter foraging
behavior of predators like the bobcat, thus resulting in a spatial response by
bobcats (Crabtree and Wolfe 1988, Gasaway et al. 1992, Godbois et al.
2004, Jones et al. 2002, and Vander Lee et al 1999). It has been reported that
bobcats on our study site are found 10 times closer to supplemental food than
expected under a null hypothesis (Godbois et al. 2004). Thus, management
practices on our study site may have likely influenced bobcat home-range
sizes by maintaining abundant prey.
Seasonal home-range sizes differed by gender. Male home ranges were
larger than females during all seasons except fall 2001. An exceptionally
large home range of one female (Bobcat #27, 18.4 km2) may have contributed
to the average female home range for fall 2001 being greater than the
average male home-range size during that season. Although male seasonal
home-range sizes did not differ significantly, we observed that males had the
greatest home ranges during winter in all 3 years, suggesting that male
bobcats may have increased their home ranges during the breeding period to
provide greater breeding opportunities by overlapping more female home
ranges (Anderson and Lovallo 2003).
Female home-range sizes varied seasonally. The average home-range
size during winter 2003 was greater than 9 of the other 10 seasons, which
explains the seasonal variation in home-range size for female bobcats and
2006 J.C. Cochrane, J.D. Kirby, I.G. Jones, L.M. Conner, and R.J. Warren 719
the interaction between gender and season as predictors of home-range size.
Three female bobcats had atypically large home ranges during winter 2003;
Bobcats 40, 6, and 18 had home-range sizes of 34.7 km2, 17.5 and 14.0 km2,
respectively. While we can not explain why their home ranges were greater
during this season, we are confident that the large home ranges exhibited by
these animals are responsible for the large mean home ranges during this
season. The smallest female home ranges occurred during summer 2002,
during the period of the year that females provide prey to kittens (Bailey
1979, Jackson and Jacobson 1987).
Similar to most studies of home-range overlap among bobcats, we found
that there was more intersexual overlap than intrasexual overlap and that
male home ranges typically overlapped at least 2 female home ranges
(Anderson 1987, Buie et al. 1979, Hall and Newsom 1976, McCord and
Cordoza 1982, Marshall and Jenkins 1966, Miller and Speake 1979,
Whitaker et al. 1987). It has been observed frequently that male home ranges
overlap several female home ranges and other male home ranges (Anderson
1987, Bailey 1974, Buie et al. 1979, Hall and Newsom 1976, Miller and
Speake 1978, Nielsen and Woolf 2001, Whitaker et al. 1987) and that female
home ranges are typically exclusive of other females (Anderson 1987, Buie
et al. 1979, Hall and Newsom 1978, Marshall and Jenkins 1966, Miller and
Speake 1979, McCord and Cordoza 1982, Whitaker et al. 1987). However, a
few other studies found that female and male bobcats maintained shared
portions of their home range with other bobcats of the same gender (Chamberlain
and Leopold 2001, Diefenbach et al. 2006, Nielsen and Woolf 2001).
We observed that male-male overlap was less pronounced than femalefemale
overlap. We speculate that abundant prey resources on our study site
permitted female bobcats to share portions of their home range with other
females; male bobcats, on the other hand, were less tolerant of other males in
an attempt to maintain exclusive breeding opportunities.
Contrary to a hypothesis proposed by Bailey (1981), who suggested that
female home ranges should be smaller and more exclusive in warmer regions
where resources are abundant and evenly distributed, female bobcats on our
study area did not maintain spatial exclusivity. Although abundant resources
existed throughout the study area, there were examples where individual
home ranges of females were overlapped entirely by other females, similar
to that reported by Chamberlain and Leopold (2001). Conner et al. (1999)
suggested that experience leads to increased hunting success and efficiency,
which would cause home-range size to decrease (i.e., time-in-residence). It
is possible that females with more experience and hunting efficiency also
share space with other females (Chamberlain and Leopold 2001). Genetic
relatedness also may influence sharing of space between individuals of the
same gender (i.e., females on our study site).
Knick (1990) concluded that a decrease in prey abundance caused bobcats
to wander and led to a breakdown in land tenure; we suggest that an
increase in prey abundance also may lead to a relaxation of land tenure,
720 Southeastern Naturalist Vol. 5, No. 4
agreeing with the hypothesis that defending an exclusive area is most energetically
feasible when resources are at an intermediate level (Brown 1964,
Krebs and Davies 1993, Maher and Lott 2000, Wittenberger 1981). Spatial
exclusivity within bobcat populations likely occurs at an energetic expense;
thus, when resources are abundant, it may be more energetically profitable to
relax land tenure and tolerate the presence of other consexuals than to defend
a resource that is not limiting.
Future research should address effects of prey abundance on bobcat
home-range size and overlap. Without designed experiments, a meta-analysis
of existing data may provide evidence to substantiate or refute the
hypothesis that land tenure in bobcats breaks down at high and low prey
abundances. The potential relationship between genetic relatedness and
home-range overlap would address the likelihood that related consexuals are
more likely to share space. Finally, effects of time-in-residence on homerange
overlap should be addressed to further provide insight about factors
that may affect spatial organization in bobcats.
Funding and other support was provided by the Joseph W. Jones Ecological
Research Center, University of Georgia, and Georgia Department of Natural Resources.
S.B. Castleberry, M. Tarrant, and R.L. Hendrick, Jr. provided editorial
assistance. We thank the Jones Center Wildlife Lab, especially B. Rutledge, J. Wade,
R. Varnum, B. Cross, M. Perkins, A. Subalusky, B. Howze, and A. Reid for trapping
assistance. Several Jones Center personnel, especially B. Bass, M. Melvin, and A.
Sheffield, also provided critical help with other aspects of our field work.
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