2010 SOUTHEASTERN NATURALIST 9(3):547–562
Male Swamp Rabbit (Sylvilagus aquaticus) Habitat
Selection at Multiple Scales
Karen B. Vale1, and Robert E. Kissell, Jr.1,*
Abstract - Sylvilagus aquaticus (Swamp Rabbit) is of conservation concern
throughout portions of its range, primarily due to habitat loss and alteration. Understanding
habitat selection is requisite for natural resource managers providing
suitable habitat to support populations of Swamp Rabbits. Swamp Rabbits are
thought to be territorial and, as such, emphasis should be placed on males when
studying habitat selection. Seasonal (dormant, growth, and senescent) habitat
selection by male Swamp Rabbits was assessed at landscape, home-range, and
plot scales. In each season, young (<20 yr) bottomland hardwood forests were selected
in greater proportion, open field was selected intermediately, and old (>35
yr) bottomland hardwood forests were selected least relative to availability at the
landscape scale. Male Swamp Rabbits selected home ranges from the landscape
to include access to higher-elevation habitats, perhaps important during flood
events. At the home-range scale, young bottomland hardwood forests and open
fields were selected most during the dormant and senescent seasons, respectively,
and old bottomland hardwood forests were selected least during the senescent
season; the remaining cover types in each season were selected in proportion to
their availability. At the home-range scale, locations with suitable cover were
selected suggesting predation-risk was important at this scale. At the plot scale,
predictor variables indicated Swamp Rabbits selected sites conducive to daytime
resting, nighttime foraging, or latrine use. We present the first work that examines
habitat selection of male Swamp Rabbits at multiple scales. Our results emphasize
the importance of interspersion of cover types and stand age selected by male
Habitat selection, the active process of choosing habitat at different
scales, can drive distribution patterns because animals do not use the
available habitat uniformly within their range (Hall et al. 1997, Krebs
1994). Habitat selection affects fitness, and animals select higher quality
habitat within their range when available (Manly et al. 2002). Furthermore,
habitat selection results in disproportional use of some resources
and can occur across multiple scales (Hall et al. 1997, Johnson 1980).
Distribution and selection of resources are thought to determine spatial
organization, including home ranges and territories (Brown and Orians
1970). Male Sylvilagus aquaticus Bachman (Swamp Rabbits) are largely assumed
to be territorial (Chapman and Flux 2008, Kjolhaug and Woolf 1988).
1School of Forest Resources, Arkansas Forest Resources Center, University of
Arkansas at Monticello, Monticello AR 71656. *Corresponding author - kissell@
548 Southeastern Naturalist Vol. 9, No. 3
If males defend feeding or mating territories, then determining habitat selected
by males is important for management, as reproductive success would
depend upon understanding habitat characteristics of these locations and
factors affecting habitat selection.
Limited knowledge exists regarding the habitat ecology of Swamp
Rabbits (Chapman and Feldhamer 1981). Much work has been conducted
on distribution (Fowler and Kissell 2007, Scheibe and Henson 2003, Terrel
1972), occupancy (Roy Nielson et al. 2008), and latrine characteristics
(Fowler and Kissell 2007, McCollum and Holler 1994, Zollner et al. 1996).
Given the assumption that Swamp Rabbits are territorial, however, there
is a gap in our understanding of male Swamp Rabbit ecology. Considering
that the swamp rabbit is of conservation concern in portions of its range
(Dailey et al., 1993, Kjolhaug et al. 1987, Korte and Fredrickson 1977),
that it is assumed to be territorial, and that a paucity of information exists
regarding the species, we assessed seasonal habitat selection by male
Swamp Rabbits at the landscape (2nd order), home-range (3rd order), and
plot (4th order) scales to determine cover types and habitat components
most important in the core of its range.
The study area, 91.9 ha in size, consisted of both private and industrial
forest in Drew County, AR (33º25′N, 91º56′W). The industrial forest had
active timber management on the site. Four cover types were identified:
open field (OF); young bottomland hardwood forest (YBHF; <20 yrs); old
bottomland hardwood forest (OBHF; >35 yrs), and clear cut (CC; <4 yrs).
The OF was dominated by Andropogon spp. and Festuca spp. (various
grasses) and contained several food plots. The YBHF was clear cut in 1990
(17%) and 1997 (87%) and allowed to regenerate naturally. The YBHF
overstory was dominated by Quercus spp. (oak), Liquidambar styraciflua
L. (Sweetgum), Carpinus caroliniana Walt. (American Hornbeam), and Ulmus
alata Michx. (Winged Elm). The understory in the YBHF was diverse,
but was primarily dominated by American Hornbeam, oak, Vaccinium
spp., and Crataegus marshallii Eggl. (Parsley Hawthorn). Numerous paths
3–5 m wide were distributed throughout the YBHF. Portions of the OBHF
were selectively cut in 1936 and 1976. The overstory was dominated by
oak, American Hornbeam, and Sweetgum. The understory was sparse and
dominated by Amercian Hornbeam, Vaccinium spp., and Ilex opaca Aiton
(American Holly). The CC was cut in 2004 and was replanted with Pinus
taeda L. (Loblolly Pine). Typical species other than pine included Rubus
spp., Vaccinium spp., and Baccharis halimifolia L (Eastern Baccharis).
Elevation ranged from 30.32–34.01 m and was different among cover types
(CC [mean = 33.16 m] > OF [mean = 32.99 m] > YBHF [mean = 31.99 m]
> OBHF [mean = 31.54 m]).
2010 K.B. Vale and R.E. Kissell, Jr. 549
Brown’s Creek intersected the study site, and a network of channels
and sloughs branched off throughout the site. Seasonal flooding occurred
throughout the study area, and portions of the site were inaccessible during
periods of flooding. Mean annual temperature was 19.2 °C and ranged from
-6.1 °C in January to 40.0 °C in August (NWS 2006–2008). Precipitation
totaled 78.4 cm and ranged from 2.4 cm in August to 17.8 cm in July (NWS
Forty collapsible Tomahawk live traps (70 x 25 x 25 cm; Tomahawk
Live Trap Company, Tomahawk, WI) were set in areas where latrine sites,
runs, and tracks indicated rabbit activity. Traps were placed ≥1 month in
advance to habituate rabbits to their presence. Traps were covered with
burlap and baited with various baits (Smyth et al. 2007). Trapping sessions
of 2–22 days in length ran from 8 December 2006 to 25 March 2007,
with traps checked daily. Captured rabbits were anesthetized using an
intramuscular injection of 10 mg/kg ketamine hydrochloride and 2 mg/kg
xylazine hydrochloride. Rabbits were weighed (g), measured (mm; hind
foot length, ear length, tail length, total body length, and chest girth), and
identified to sex. Rabbits weighing ≥1800 g were each fitted with a radiocollar
(30–40 g) equipped with a 12-hr delay mortality sensor (Advanced
Telemetry Systems, Isanti, MN); collars weighed <4% of the body weight
as suggested by Cochran (1980). Each rabbit also received a numbered ear
tag in each ear (Seber 1982; National Band and Tag Company, Newport,
KY). Captured Swamp Rabbits were allowed to recover from sedation and
released at the site of capture. Capture, handling, and release of Swamp
Rabbits were performed following methods which adhered to the guidelines
of the American Society of Mammalogists (Gannon et al. 2007) and
were approved by the University of Arkansas at Monticello Institutional
Animal Care and Use Committee (Approval #2006-2).
Collection of telemetry-based locations began ≥48 h post-capture to allow
for recovery from the stress of capture. Collared rabbits were located
2–3 times per week for the study duration, until death, or until transmitter
failure. Rabbits were located during 4 time blocks: early morning (00:01–
6:00 hr), late morning (6:01–12:00 hr), mid-day (12:01–18:00 hr), and
evening (18:01–24:00 hr). We used 3 seasons to determine habitat selection.
Seasons, based on general plant phenology, were dormant (January–March),
growth (April–June), and senescent (July–October).
Permanent telemetry stations (n = 21) were established throughout
the study area utilizing a Trimble GeoXH Global Positioning System
(GPS) unit. Rabbit locations were determined by triangulation (White and
Garrott 1990, Zollner 1993) using an R-1000 telemetry receiver (Communications
Specialists, Inc., Orange, CA) and an H-antenna. Azimuths were
550 Southeastern Naturalist Vol. 9, No. 3
recorded from 2 telemetry stations for each rabbit, and the intersection
was considered the animal’s location (Heezen and Tester 1967, Herring
and Collazo 2005, Nams and Boutin 1991). Bearings were taken ≤10
minutes apart. Only bearings having a difference of 60–120° were used.
Universal Transverse Mercator coordinates of radio-collared Swamp Rabbits
were determined using program Locate II (Nams 1990). Accuracy of
bearing acquisition was determined seasonally using radio-collars placed
at known locations.
Fixed kernel estimates (50, 90, and 95% contours; Kernohan et al.
2001, Seaman and Powell 1996, Seaman et al. 1999) were calculated using
the ad hoc bandwidth method (Schroeder 2007) utilizing Home Range
Tools for ArcGIS (Rodgers et al. 2007). The ad hoc bandwidth method is
similar to least squares cross validation in that the reference bandwidth
is reduced gradually, but the ad hoc bandwidth is chosen just before the
95% kernel home range contour is separated into >1 polygon (Schroeder
2007). Choosing a bandwidth just before the contour is separated into >1
polygon provides connectivity among all areas of the home range. Seasonal
home ranges were calculated only for animals with ≥30 locations
(Seaman et al. 1999).
We developed a cover-type map by digitizing a 2006 aerial photograph
for 2nd and 3rd order habitat selection. Cover types within the study area
boundary were classified based on management history and vegetative
characteristics. The study site boundary was determined by buffering all
rabbit locations a distance of one-half the mean maximum distance moved
(Wilson and Anderson 1985). Only 1 male rabbit’s home range included CC;
therefore, this cover type and rabbit were omitted from 2nd and 3rd order assessments.
Available habitat was determined using 1000 randomly selected
points within the study area for 2nd order selection. Available 3rd order habitat
was determined using 30 randomly selected points within each 95% fixed
kernel home range.
Fourth-order selection was quantified by measuring vegetation and
other physical characteristics from 20 April 2007–20 March 2008 at
rabbit locations identified by radio-telemetry and at random locations.
Random locations were identified with random distances and bearings
from rabbit locations, and were between 50–250 m from estimated rabbit
locations (Porath 1997, Seamans and Guttierrez 1995).
We measured mean canopy cover using a concave densitometer; 1
measurement was taken at plot center and, 4 measurements were taken
5 m from plot center in each cardinal direction (Zollner 1993, Zollner et
al. 2000a). We measured mean horizontal visibility using a 0.5-m x 0.5-m
density board (Wagner et al. 2000) to indicate understory vegetation cover.
2010 K.B. Vale and R.E. Kissell, Jr. 551
Density-board measurements were taken in each cardinal direction 10 m
from plot center. We measured horizontal visibility from ground level to
0.5 m above ground and from 0.5 m to 1 m above ground. Downed logs
and stumps ≥7.6 cm diameter and within 10 m of plot center were enumerated
and measured (Payer and Harrison 2003). Measurements included decay
class (Brown et al. 1998, Dingledine and Haufler 1983), log circumference
(at center), and presence of moss and rabbit fecal pellets (Fowler and Kissell
2007). Decay classes were 1–6, with a greater number indicating more decay.
Latrines within 10 m of each location were also enumerated. Number of pellets
present and type of latrine (stump, log, or ground) were recorded. Latrine
sites were characterized as sites with at least 1 fecal pellet, and pellets within
1 m of each other were considered 1 latrine site (Zollner et al. 1996).
We measured the distance from plot center to permanent and temporary
water sources using GIS. Temporary water included ephemeral pools and
sloughs holding water for ≥1 month but not more than 9 months. Permanent
water sources were those holding water for 10–12 months per year.
We measured distance between animal locations and each of the 4 cover
types using GIS. Tree density and composition were measured using the
point-quarter method (James and Shugart 1970). The nearest tree in each
quarter was identified to species, and diameter at breast height (dbh) and
distance from plot center (m) were measured. Only trees with a dbh of
≥10.2 cm (Ellis and Whelan 1978, Korte 1975) and >5 m tall (McCollum
1992) were included. Shrub density and composition were measured
using the same methods as tree density and composition, except the nearest
shrub in each quarter was identified to species, and distance (m) and
height (m) were measured. Only shrubs with a dbh of <10.2 cm and height
of 1–5 m were included (Fischer and Holler 1991, McCollum 1992). Plant
nomenclature followed Miller and Miller (2005). Density of understory
vegetation >5 m tall and with a dbh <10.2 cm was measured by counting
the number of stems within five 2-m2 quadrats: one at plot center and one
5 m from plot center in each cardinal direction.
Ground cover was quantified by ocular estimation using five 1-m2 sampling
quadrats and 6 coverage classes at each site. Percent cover for grasses/
sedges, bare ground, vines, forbs, leaf litter, and other were recorded. The 6
cover classes were 0–5%, 6–25%, 26–50%, 51–75%, 76–95%, and 96–100%
(Daubenmire 1959). Quadrats were placed at plot center and 5 m from plot
center in each cardinal direction. We recorded the presence of browse species,
including Bignonia capreolata L. (Crossvine), Smilax spp. and Rubus
spp. (briar), Gramineae (grasses), Carex spp. (sedges), Toxicodendron
radicans (L.) Kuntze (Poison Ivy), and Arundinaria gigantea (Walter) Muhl.
(Giant Cane), within 10 m of plot center. Data on maximum and minimum
daily temperature and precipitation during the study were obtained from the
Monticello Municipal Airport, located approximately 29 km from the study
area (NWS 2006–2008).
552 Southeastern Naturalist Vol. 9, No. 3
We analyzed habitat selection at the landscape and home-range scales
(i.e., 2nd and 3rd orders) using Euclidean distance analysis (DA; Conner and
Plowman 2001). We chose DA because it provides desirable characteristics
to analyze habitat selection (Aebischer et al. 1993), is robust to telemetry
error, and provides results that allow for the evaluation of effect size. Additionally,
DA performs well in terms of meeting type-I error rates compared
to other techniques (Bingham and Brennan 2004).
The DA approach uses the ratio of distances to each cover type from
known locations of each animal to the distances from random locations to
each cover type to determine if habitat use is random. If use is random, the
ratio should equal 1. If the ratio is <1 then the animal uses the cover type
more than expected and if the ratio is >1 then the animal uses the cover
type less than expected. We used GIS to calculate the vectors of distance
ratios (di) for each cover type. We used multivariate analysis of variance
to determine if random locations differed from Swamp Rabbit locations at
both the landscape and home-range scales. If differences were found, we
used a t-test to determine which cover types were used non-randomly. The
t-tests were used for pairwise comparisons to determine if a given cover
type was used significantly more than another. We ranked cover types by
season based on increasing values of di (Conner and Plowman 2001). Statistical
Analysis Software version 9.1 (SAS Institute, Inc. 2002–2003) was
used to perform the DA using α = 0.05.
At the plot scale (i.e., 4th order), we analyzed factors affecting habitat selection
at rabbit locations in each season using stepwise logistic regression.
Variables not normally distributed or showing evidence of heteroscedasticity
(P ≤ 0.05) were transformed to meet assumptions of parametric statistical
analysis. Count and percentage data were log and arcsine square root transformed,
respectively. Only uncorrelated (r2 < 0.60) habitat variables, as
determined by Pearson correlation, were included in logistic regressions.
Variables were entered into the model at α = 0.10 and were retained in the
model at α = 0.15. Statistical Analysis Software version 9.1 (SAS Institute,
Inc. 2002–2003) was used to perform logistic regression.
Fourteen Swamp Rabbits were captured, including 3 adult females, 10
adult males, and 1 juvenile male; of these, 5 recaptures occurred. All 13
adult Swamp Rabbits were fitted with radio-collars, but we only included
adult males in the analyses. Mean bearing error of location acquisition was
8.6° (SE = 0.8). Mean distance between telemetry stations and known collar
locations was 107.3 m (SE = 8.0). Sufficient data was collected during the
dormant, growth, and senescent seasons such that we used 6, 8, and 6 male
rabbits, respectively, in landscape and home-range scale analyses.
At the landscape scale, Swamp Rabbits selected cover types disproportionately
(Table 1) during the dormant (F3,3 = 3108, P < 0.001), growth
2010 K.B. Vale and R.E. Kissell, Jr. 553
(F3,5 = 15016, P < 0.001), and senescent seasons (F3,3 = 172349, P <
0.001). Each season, male Swamp Rabbits were found closer to YBHF
and OF than expected, and farther from OBHF than expected. The pattern
of selection was consistent across seasons, and use differed significantly
among cover types within each season. Ranking was YBHF > OF >
OBHF each season.
At the home-range scale, Swamp Rabbits selected cover types disproportionately
during the dormant (F3,3 = 202.7, P = 0.001) and senescent
(F3,3 = 8.16, P = 0.059) seasons (Table 2); during the growth season, cover
types were used in proportion to availability (F3,5 = 1.08, P = 0.437). Male
Table 1. Landscape-scale (2nd order) habitat selection results using the Euclidean distance
analysis for male Swamp Rabbits in southeastern Arkansas from January 2007–October 2007
Season Cover typeA SelectionB MeanC DifferenceD
Dormant OF > -0.451 A
YBHF > -0.984 B
OBHF < 0.449 C
Growth OF > -0.515 A
YBHF > -0.974 B
OBHF < 0.481 C
Senescent OF > -0.601 A
YBHF > -0.983 B
OBHF < 0.686 C
AOF = open field, YBHF = young bottomland hardwood forest, and OBHF = old bottomland
BSelection compared to expected.
CDifference between the expected vector of distance ratios of used versus available and 1.
DDifferent letters indicate a significant difference in the use between cover types.
Table 2. Home-range scale (3rd order) habitat selection results using the Euclidean distance
analysis for male Swamp Rabbits in southeastern Arkansas from January 2007–October 2007.
Season Cover typeA SelectionB MeanC DifferenceD
Dormant OF = -0.017 A
YBHF > -0.893 B
OBHF = 0.111 A
Growth OF = -0.031 A
YBHF = -0.478 A
OBHF = 0.107 A
Senescent OF > -0.216 A
YBHF = -0.197 AB
OBHF < 0.113 B
AOF = open field, YBHF = young bottomland hardwood forest, and OBHF = old bottomland
BSelection compared to expected.
CDifference between the expected vector of distance ratios of used versus available and 1.
DDifferent letters indicate a significant difference in the use between cover types.
554 Southeastern Naturalist Vol. 9, No. 3
Swamp Rabbits were found closer to YBHF than expected and used OF
and OBHF in proportion to their availability during the dormant season.
Use differed between the YBHF and the other cover types within the
dormant season. Ranking was YBHF > OF > OBHF during the dormant
season. Male Swamp Rabbits were found closer to OF than expected,
farther from OBHF than expected, and used YBHF in proportion to its
availability during the senescent season. Use differed between the OF
and OBHF cover types within the senescent season; use of the YBHF did
not differ between the other two cover types. Ranking was OF > YBHF >
OBHF during the dormant season.
We analyzed 267 rabbit locations (dormant, n = 73; growth, n = 85; senescent,
n = 109) and 267 random locations (dormant, n = 73; growth, n =
85; senescent, n = 109) for plot-scale assessment. Twenty-five variables had
Pearson correlation coefficients < 0.60 and were used in logistic regressions.
Plot-scale results (Table 3) indicated rabbit locations contained 29.7% higher
understory cover, logs 2.8% more decomposed, 33.0% more stumps with
moss, and 31.7% more forb ground cover compared to random locations
during the dormant season. During the growth season, rabbit locations were
31.5% further away from old bottomland hardwood forest, contained logs
8.3% larger in diameter, and had 53.5% less bare ground cover compared to
random locations. During the senescent season, rabbit locations contained
logs 3.3% larger in diameter, 58.0% more ground cover of vines, and 31.2%
less bare ground cover compared to random locations.
Higher elevation sites, such as those in the YBHF and OF, serve as an important
refuge during flood events (Conaway et al. 1960, Hastings 1954, Smith
and Zollner 2001, Smyth et al. 2007). There was extensive flooding on the
study site during the dormant season; OBHF was used significantly less during
this time, indicating Swamp Rabbits moved away from flood water and used
Table 3. Seasonal logistic regression models that best separated male Swamp Rabbit locations
(n = 267) from random locations (n = 267) at 4th order scale of habitat selection (January
Season Variable d.f. Estimate SE Wald chi-square P-value
Dormant Density board visible 1 -0.5883 0.24 5.8140 0.0159
Log decomposition 1 -6.6381 3.30 4.0519 0.0441
Stumps with moss 1 -0.2185 0.13 2.7440 0.0976
Forb ground cover 1 -9.0790 3.05 8.8365 0.0030
Growth Distance to OBHF 1 -0.1115 0.05 4.8593 0.0275
Log diameter 1 -2.4577 1.15 4.6002 0.0320
Bare ground cover 1 -5.7487 2.01 8.1902 0.0042
Senescent Log diameter 1 -1.6018 0.75 4.5382 0.0331
Vine ground cover 1 -2.6526 1.61 2.7251 0.0988
Bare ground cover 1 -4.5481 1.73 6.8981 0.0086
2010 K.B. Vale and R.E. Kissell, Jr. 555
upland areas more frequently. Flooding is typical in bottomland hardwood forests,
and may cause mortality (Hastings 1954), higher vulnerability to hunting
and predator pressure (Layne 1958), and decreased availability of food and
cover (Korte 1975). YBHF provided a combination of higher elevation and
suitable cover. Although OF was selected intermediately, it may be important
for rabbits to have access to this cover type, or a similar, higher-elevation
cover type, to have refuge during flooding events. Zollner et al. (2000b) found
female Swamp Rabbits used cover types differently in response to flooding.
Smith and Zollner (2001) recognized the effect of seasonal flooding on habitat
use of Swamp Rabbits in Arkansas and suggested habitat quality may depend
on the availability of adjacent, upland areas as much as the composition and
structure of lowland areas. Flooding events may occur at any time of year on
the site we studied. Swamp Rabbits likely selected home ranges from the landscape
to minimize the effect of flooding, and selected areas that maximized
cover and refuge from flooding events.
At the home-range scale during the dormant season, males selected locations
within the YBHF most often perhaps due to availability of cover and
food resources. Considering Swamp Rabbits are opportunistic feeders that
adapt to a variety of food sources, such as grasses, sedges, woody stems,
forbs, tree seedlings (Terrel 1972, Toll et al. 1960), and given the high availability
of forage year round in the southeastern United States (Allen 1985),
available cover may be more important than available forage at this scale.
Cover is the most critical factor required by Swamp Rabbits (Allen 1985),
and we think Swamp Rabbits were selecting locations within their home
ranges based on predation risk rather than food availability. The other cover
types were used in proportion to their occurrence, and this result reflects the
limited amount of either cover type that occurred in the home ranges during
YBHF had a dense understory layer of saplings, shrubs, and groundcover
due to a moderately open canopy following clear cutting in 1997.
This cover type provided ample food and cover resources essential for
suitable Swamp Rabbit habitat (Allen 1985, Whitaker and Abrell 1986).
Lay and Taylor (1943) suggested 10–15 yr-old clear-cut areas with established
dense brush were optimum Swamp Rabbit habitat in Texas. Several
studies suggest moderate-sized clear cuts and improvement cuts as a way
to enhance Swamp Rabbit habitat by creating canopy gaps to increase understory
density (Hurst and Smith 1986, Korte 1975). For example, Korte
(1975) suggested creating openings 0.1–0.5 ha several hundred meters
apart in even-aged forests to improve habitat for Swamp Rabbits in Missouri.
Likewise, Hurst and Smith (1986) recommended a silvicultural
practice that includes 4–8 ha clear cuts and periodic improvement cuts
throughout a stand’s rotation in Mississippi.
Cover types were selected in proportion to their availability during
the growth season at the home-range scale. Extensive vegetative growth
556 Southeastern Naturalist Vol. 9, No. 3
throughout the study area may have enabled rabbits to move into areas not
typically used during other seasons. Grasses within the OF were tall enough
to provide cover from predators during the growth season, and rabbits may
have been more apt to use the OF as a result. Likewise, vegetative growth
in the OBHF also likely provided sufficient cover and forage to be used in
proportion to its availability. The importance of habitat selection in rabbits
is most often related to cover and avoiding predation (Iason et al. 2002), but
the importance of cover for rabbits may be seasonal (Rueda et al. 2008).
Rabbits will make use of areas with more vegetation, especially during the
growth season, when vegetation provides for both forage and cover (Rueda
et al. 2008).
The senescent season was the driest and hottest season, and the OF was
cut during this time. Associated with the reduced available cover in the OF
was access to new plant growth. Conversely, Swamp Rabbits likely limited
their time in the OBHF because of the limited and desiccated forage and
lack of cover. The YBHF likely provided cover and was in proximity to the
OF. This combination of cover types likely satisfied the need for cover and
forage during this time of the year.
In all seasons at the plot scale, habitat variables predicting Swamp Rabbit
locations appeared related to latrine use, foraging, or daytime resting sites
(Zollner et al. 2000a). During the dormant season, greater shrub cover related
to daytime resting sites, greater decomposition of logs and greater numbers
of stumps with moss related to latrine sites, and greater ground cover of
forbs were reflective of foraging areas. Zollner et al. (2000a) found daytime
resting sites correlated with higher percentage of shrubs and downed tree
tops in Arkansas, habitat factors which they attributed to predator avoidance
and weather-related hazards. Allen (1985) postulated optimum shrub canopy
closure as ≥50%; we found mean shrub cover at rabbit locations to be ≈69%.
Although methodology varied with these studies, results illustrate the importance
of a dense shrub layer for Swamp Rabbits.
We also found highly decomposed logs and mossy stumps to be important
predictors of rabbit locations during the dormant season. Highly decomposed,
mossy logs and stumps are known to serve as latrine sites (Fowler
and Kissell 2007, Smyth et al. 2007, Zollner et al. 1996). If latrine sites are
used for information exchange or territorial marking, the rotted, mossy substrate
may act as an absorptive surface allowing olfactory scent to last longer
(Sneddon 1991, Zollner et al. 1996). Amount and decomposition of woody
debris varies with stand age and development, and although young clear cuts
have been found to have increased amounts of coarse woody debris (Patterson
et al. 2008), decayed logs are generally not present (Idol et al. 2001,
McCarthy and Bailey 1994). Stands 10–100 yrs old typically have fewer
logs, but are more decomposed (Idol et al. 2001, Jenkins and Parker 1997).
Swamp Rabbits may have selected locations within the stand old enough to
contain adequately decomposed woody debris.
2010 K.B. Vale and R.E. Kissell, Jr. 557
Swamp Rabbits are opportunistic feeders and have been found to consume
plants in order of their abundance (Toll et al. 1960). However, Fowler
and Kissell (2007) noted the importance of B. capreolata in swamp rabbit
occurrence in Arkansas. During the dormant season, there was not an
abundance of forbs on this site. Garner (1969) found Swamp Rabbits fed
primarily on forbs during the spring (62%) and summer (94%) in Louisiana;
winter forage consisted primarily of grasses (77%). However, results indicated
Swamp Rabbits were selecting sites with more forbs available despite
being in low abundance.
During the growth season, greater distance to OBHF, greater log diameter,
and less bare ground cover were likely related to daytime resting
sites, latrine sites, and foraging areas, respectively. The OBHF had dense
overstory canopy cover (mean = 87.1% at rabbit locations), outside the
range (25–60%) suggested by Allen (1985) for optimal overstory canopy
closure. Greater overstory canopy cover reduced the amount of understory
vegetation, such as saplings, shrubs, forbs, vines, and grasses, which may be
utilized as cover or food by Swamp Rabbits.
Similar to the decomposition of logs and number of mossy stumps,
greater log size is likely related to latrine use. Whitaker and Abrell (1986)
suggested Swamp Rabbits use elevated objects to get a better view of their
surroundings and reduce predation risk. Results indicated log height may
have been important for Swamp Rabbits during the growth season when
greater vegetative growth may have obstructed their view. Zollner et al.
(2000a), however, did not find a relationship between shrub ground cover
and sites used as latrines during spring–summer (May–August) or fall–
winter (October–January) seasons.
Less bare ground cover used during the growth season may have been a
result of the abundance of the other ground-cover categories available during
this season, none of which were important by themselves. Areas with
less bare ground were more likely to have more forage items, such as forbs,
grasses, and vines.
Greater log size, less bare ground cover, and more vine cover during the
senescent season represented latrine use, foraging areas, and daytime resting
areas. If Swamp Rabbits were using larger logs during times of greater
vegetative growth to improve their view, larger logs should be less important
during the senescent season. However, Swamp Rabbits were using larger
logs despite the reduction of vegetative growth. Our findings are not consistent
with the vigilance hypothesis put forth by Whitaker and Abrell (1986),
and the importance of log size remains unknown.
Vines are an important food source for Swamp Rabbits (Allen 1985, Smith
1982). Low tangles of vines also provide excellent cover for Swamp Rabbits
(Allen 1985). There was an abundance of vines available throughout the study
period, but they may have become more important as food and cover during
the senescent season when herbaceous vegetation decreased in abundance.
558 Southeastern Naturalist Vol. 9, No. 3
It appears that male Swamp Rabbits in southeastern Arkansas selected
home ranges at the landscape scale to include higher elevation habitats
needed during times of flooding, suitable cover and forage at the homerange
scale depending on season, and fine-scale variables to provide for
maintenance activities at the plot scale. This is the first assessment of habitat
selection at multiple scales that demonstrates the importance of the spatial
and temporal use of cover types by Swamp Rabbits.
We thank the University of Arkansas at Monticello for providing funding, and the
Hyatt Family and Larson and McGowin, Inc., for use of their land. We are grateful
to J. Earl, J.P. Kenny, J. Kidd, and B. Smyth for assistance with data collection. We
also thank R. Booker for assistance with plant identification.
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