TECHNICAL REPORT NO. 4
SPATIAL DISTRIBUTION OF BOBCATS
AND GRAY FOXES IN EASTERN FLORIDA
R. F. Labisky, Principal Investigator
D. R. Progulske, Jr., Project Investigator
School of Forest Resources and Conservation
Institute of Food and Agricultural Sciences
University of Florida, Gainesville, FL 32611
Submitted to:
Cooperative Fish and Wildlife Research Unit
University of Florida
Gainesville, FL 32611
Supported by:
U.S. Department of the Interior
Fish and Wildlife Service
Contract No. 14-16-0009-79-062
September 1982
ACKNCLECGEENIS
This project was funded jointly hy the Florida
Cooperative Fish and Wildlife Research Unit and the School
of Forest Resources and Conservation, University of Florida.
Technical advice was provided ty: Cr. Sicaard W.
Grjeory, Leader, Florida Ccoperative fish and Wildlife
Research Unit; Dr. F. fayne Kiny, Director, Florida State
Iuseum; Dr. Stephen Hiumphrey, Associate Curatcr of
Ecology, Florida State Museum; and James P. Erady,
Supervisory Biologist, bureau of Wildlife Bosearch, Florida
Game and Fresh water Fish Ccimission.
Thanks are also due tne fcllcwinq individuals: Mark C.
Conner assisted with all phases of the research study;
Harold Gcrnto and his starr, University of F~crida researchh
and Education Center at Welaka, expedited field work and
provided excellent facilities; DLuglas Ducant furnished
morai support and occasicual overnight lodqinq; D. W.
Tredinick alicwed access to nis prcperty to radio-tracx
boLcats; and Julie A. Hcvis assisted in tne preparation or
tne report.
TAELE CF CONIEhIS
PAGE
ACKNOWLEDGMENTS...................................... ii
EXECUTIVE SUMMA3Y....................................... v
PREFACE...................................... ......... x
PART 1
SPATIAL DISTRIBUTIONS CF ECBCATS
AND GRAY FOXES IN EASTERN FLCIL.................... 1
INTRODUCTION..... .............................. 1
STUEY AREA....................................... 3
METHODS ......................................... 6
Field Collection.................... ......... 6
Data Analysis.................................. 8
RESULTS.................... ..................... 12
Gray Foxes......................... ........ 12
Home Range Size................. .......... 12
Core Area Size........................... 1
HUcm Range and Ccre Area Cverlap.......... 14
Activity Patterns......................... 19
Daily Movement Patterns.. ............... 22
Habitat Use. ...... .... ................... 22
Bobcats..................... .............. 27
Hcme Range Size....... ........ ............ 33
Activity Patterns........................... 36
Daily Movement Patterns........ ............ 36
Habitat Use.................. ............. 36
DISCUSSIc ...................................... 43
Gray Fox ........ ............................. 43
Hcme Range Variatility..................... 43
Daily Moveents................................... 45
BoLcats......... ..... ...... .................. 46
H~e Fauige Variability......... ..... .... 46
Daily Hovement ................ ........... 50
Gray Fox and Botcat Interactions............... 50
iii
MANAGEMENT IMPLICATICNS .... ... ............... 53
LITERATURE CITED................................ 55
PAA-T 2
SCENT-STATICN INDICES AS IIDICATCES
OF POPULATION ABUNDANCE FOR
BOBCAIS, RACCOONS, GRAY FOXES, AND OECSSUdS........ 60
INTBODUCTION.................................... 60
STUDY AREA ...................................... 62
METHCDS......................................... 64
RESULTS .............. .......................... 66
Bobcat Visitation..................... ...... 66
Baccoon Visitation ........................... 66
Gray Fox Visitation............................ 69
COossum Visitation............................ 69
DISCUSSION ...................................... 71
CCNCLUSIONS..... ................................ 75
LITELAT7 S CITED............................... 78
APPENDIX A
CAPTURE DATE, SEX, AGE, WEIGHT, AND MEASUEEMENTS
FOR GRAY FOXES CAPTURED ON THE WEIAKA STUDY AREA,
1980-1 82............ ................................. 80
APPENDIX E
CAPTURE LATE, SEX, AGE, WEIGHT, AND MEASUEEMENIS
FOB EOECATS CAPTURE CON THE WELAKA SIUDY AREA,
1980-1 82 ............................... ............ 82
EXECUTIVE SUMMARY
Part 1: Spatial Distributions of Bobcats and Gray Foxes
in Eastern Florida
Home ranges and movements were determined by
radio-telemetry for a selected populatica or gray foxes
(Drocyon cinereoarienteus) and bobcats (Felis rufus) on a
150-kmz study area in ncrtaeastern ficrida. Six
radio-ccllared gray foxes, Iccated 869 times from December
1980-December 1981, had a mean hcme range size (harmonic
afan analysis) of 582 ha (range=223-1140 ha). The acme
ranges ci male and female rcxes did not differ in size
(?>0.05). Foxes were principally nocturnal; daily movements
dirfered significantly among seasons (P<0.05), hut not
between sexes (P>C.05). Daily movements of cfxes averaged
8242 m during the breeding season (Ceceinber-narch) ; 2235 m
during the denning and helping season (April-July); and
4385 m atter the young had become independent
(Auqust-Ncvember) Simultanecus estimaticn procedures
revealed that tie yray foxes preferred dense areas, such as
pine flatwcods (Pinus elliottii) curing the day, and acved
into more open areas, such as meadows and Icngleaf
pine-turkey oak sandhills (iinus Lalustris-~uercus laevis),
at night. Foxes avoided bcttczland hardwoods totally.
v
Iwc radio-collared male obhoats, located 269 times from
July 1980-December 1981, had a mean home range size
(harmonic mean analysis) of 3820 ha (range=3680-3960 ha).
Although movement activity was recorded during all hours of
the day, bobcats were chiefly nocturnal. Daily movements
averaged 6090 m. Simultaneous estimation procedures
indicated that botcats preferred tottcmland hardwoods during
day and night; a secondary preference for pine ilatwoods was
exhibited during the day. Bobcats generally avoided
habitats witA open understories during the day, and traveled
in habitats with medium understcries at night. No
significant competitive interactions were noted between the
gray foxes and botcats.
It is practical to manage for gray foxes through
habitat manipulation coupled with harvest regulation.
However, due to the solitary tehavicr of bobcats, tne most
efficient way to manage them is tarcuqh population
mcnitoring programs together with manipulation of harvest.
Part 2: Scent-Station Indices as Indicators of
Population Abundance for Eotcats, Raccoons,
Gray Foxes and Cpcssums
Population trends of totcats, raccoons (POcc cn lotor),
gray foxes, and opossums (Didelphis virginiana) were indexed
by scent-station transects on the 918-ha Welaka Reserve.
Three permanent transects were operated for 1 night per
month for the 24-month period, January 1980-December 1981.
Each transect was comprised of 10 stations spaced at 0.32-km
(0.2 mi) intervals; each station consisted of a circle of
sifted sand 0.91 m (3 ft) in diameter with a
centrally-located cottouball that was saturated with totcat
urine. Transects were activated in the afternccn and
checked for visitation the following morning. A visit was
defined as the presence of 1 or more tracks of a species per
station. Mcntaly visitation rates (VB) were calculated for
each species for each transect for each niqLt tuat the
transects were operated. Analysis cf variance procedures
designed to test for differences between years and among
months were applied to arcsine-transfcrmed visitation rates.
Mean monthly scent-station visitation rates for the
24-month period for bobcats, raccoons, gray foxes, and
opossums were 1A, 27., 480, and 1C0, respectively. No
significant differences in the visitaticu rate for bobcats
were detected for years or mcnths (E > 0.05). However,
trends in scent-station visitation rates for bocats did
reflect independently-determined trends Lu pcrulaticn
abundance. Visitation rates ty bobcats were highest in late
fall and winter.
The scent-station visitation rate of 30% for raccoons
in 1980 was significantly ditlerent frcm th 17% rate
recorded in 1981 (P < 0.05). A period of belcw normal
rainfall, beginning in late 1980 and extending throughout
1981, probably concentrated raccoons in wetland habitats
that were not directly indexed by scent-station transects.
Thus, the lower visitation rate for raccoons in 1981, in
contrast to 1980, may have reflected a shift in habitat
utilization rather than a decrease in population abundance.
The highest monthly visitation rate by raccocns occurred in
September.
The scent-station visitation rate oz 521 icr gray foxes
in 1981 was significantly different from the 35W rate in
1980 (P < 0.05). Seasonal trends in gray fox visitation
rates reflected seasonal trends in population abundance,
i.e., rates were highest in fall (Ncvemter), when juveniles
dispersed, and lowest in spring (lay), when the adults fox
population was minimal and young roxes were restricted to
dens.
The erratic trends in monthly scent-station visitation
rates for opposums, as well as the significant interaction
between year and month, suggested that scent-station indices
were not reliable indicators cf trends in opcesum population
abundance.
viii
ITis investigation provided several specific
recommendations for indexing the population abundance of
carnivorous furbearers in Florida by scent-station
transects. If the indices for all species are to be derived
form a single network of transects that is operated once per
year, the network should be operated in October or November
and the transects should be distributed proportionately in
all major habitat types. If species-specific transect
networks are utilized, the network for bobcats and gray
foxes should be operated in Ncvember and the network for
raccoons in September. The large chme ranges or bobcats
during periods of low population density indicated that
scent-staticn indices derived from transects longer than
2.88 km miglt better reflect bobcat population abundance
because mere bobcat ncme ranges wculd be traversed by each
transect. Transects targeted specifically for raccoons
should be distributed so as to sample wetland habitats in
proportion to their availability.
PBEFACE
This report consists of 2 separate and self-contained
papers, which, after appropriate editorial Levisioa, will be
submitted for publication in technical wildlife periodicals.
PART 1: SPATIAL DISTRIEUTICKS CF BCCATS
AND GRAY FOXES IN EASIEBf FICOIDA
INTRCDUCTION
The bobcat (Felis rufus) and the gray fox (Urocyon
ScinereoarSeneus) are important mammalian predators in
Florida. The population status of the tbocat, however, has
become a recent and major concern ct conservationists
because the annual harvest of bobcats in the United States
has risen steadily during the past decade due tc an
increased demand lor pelts cf spotted cats. In Florida, the
average price per bobcat pelt has risen frcm is to $50
(900%) in the past 13 years (Spratt and Brady 1982).
The bobcat is listed on Appendix II of the Convention
on International Trade in Endangered Species of Wild Fauna
and Flora (CITES). This designation requires that countries
exporting pelts must provide information to verify that the
harvest of these animals is not detrimental tc survival of
the species. Recently, a U.S. District Court, using CITES
as a basis, issued an injunction prohibiting the U.S. Fish
and Wildlife Servics tcca authorizing tae eaxcrtaticn of
PART 1: SPATIAL DISTRIEUTICKS CF BCCATS
AND GRAY FOXES IN EASIEBf FICOIDA
INTRCDUCTION
The bobcat (Felis rufus) and the gray fox (Urocyon
ScinereoarSeneus) are important mammalian predators in
Florida. The population status of the tbocat, however, has
become a recent and major concern ct conservationists
because the annual harvest of bobcats in the United States
has risen steadily during the past decade due tc an
increased demand lor pelts cf spotted cats. In Florida, the
average price per bobcat pelt has risen frcm is to $50
(900%) in the past 13 years (Spratt and Brady 1982).
The bobcat is listed on Appendix II of the Convention
on International Trade in Endangered Species of Wild Fauna
and Flora (CITES). This designation requires that countries
exporting pelts must provide information to verify that the
harvest of these animals is not detrimental tc survival of
the species. Recently, a U.S. District Court, using CITES
as a basis, issued an injunction prohibiting the U.S. Fish
and Wildlife Servics tcca authorizing tae eaxcrtaticn of
bobcat pelts. The court indicated it was net satisfied with
the criteria imposed on the states by the U.S. Fisa and
Wildlife Service to determine the suitability cz bobcats for
harvest (Department of the Intericr 1i82).
The general status of the gray fox has not been as
controversial as that of the bobcat because it is more
abundant and is not listed by CIIES. Although harvested in
large numbers throughout the Southeast and in other regions
of the United States, few projects have been devoted to the
study of its biology (Wood et al. 1558, Lord 1961, Trapp and
Hallberg 1975, Root 1581). In Florida, because it is
illegal tc harvest gray foxes and red foxes (Vuljes vuljes),
aucn of the interest in these species has been related to
tLeir role as a carrier of rabies (kccd 1554, Jennings et
al. 1960, Mclean 1970, Carey 1982).
This study was designed to investigate the movement
patterns of bobcats and gray foxes in north Fl1cida via
radio-telemetry; to ascertain the relative use of different
habitats by each species; and to evaluate possible
interspecific competition between the species.
STULY AREA
The Nelaka Study Area, which encompasses approximately
150 kmz, is located in southern Putnam County of
northeastern Florida. The area has little tcpcgraphic
relief, with elevations varying from 3-20 m above sea level.
The soils are principally well-drained sands, although
poorly-drained muck soils cccur in some of the betterr areas
(Laessle 1942, Schultz 1979). Small lakes and po.ds are
common throughout the area. Annual mean temperature and
rainfall for the local region are 22 C and 137 cm,
respectively (National Cceanic and Atmospheric
Administration 1974).
The area is predominantly forested, being comprised of
the following plant communities: hcttcmland hardwoods; pine
flatwoods and pine plantations (Finus elliottii and Pi.us
aliustris); icngleaf pine-turkey oak sandhills (Pinus
palustriis-.uercus laevis) live oak hammocks (Gercus
vZiriniana var. viijiniana) ; orange groves (Citrus spp.);
and open fields. A detailed description of these habitats
is available in Laessle (1942), fMonk (1965), and Veno
(1976).
The ccre study area was tie 9.2 ku2 University of
Florida Welaka Research and Educaticn Center (ceiaka
Reserve), located on the east bank cf the St. Johns River
near the tcwn of Welaka (Fig. 1). The Welaka Reserve is
unique in that approximately 1/3 of the area has been
designated as inviolate since 1939. Inviolate areas have
been protected frcm all man-induced influences except fire
protection and road maintenance. Boundaries of the Reserve
are fenced except along the river. Hunting and trapping
have not been permitted on the Welaka Reserve since the late
1930's.
5
SATSUMA N
CRESCENT
LAKE
SPOMONA PARK
OCALA 8R 309A
NATIONAL 0 |O LK
LITTLE ,
LAKE GEORE Lake
A EO Eet SR 308
2 KM
Fig. 1. Map of the Welaka Study Area, Florida. The
shaded area delineates the 150-km2 Welaka Study Area.
The thin dashed-line represents the boundary of the
Welaka Reserve.
MEIBODS
Field Ccllection
Trapping of gray foxes and bobcats was conducted on the
Welaka Ueserve during January-March 1980, July-December
1980, January-March 1981, and January 1982 (post-study).
Custom-made and commercially available box-type live traps
were used to capture all animals. Twc models ot dead-bait
traps were used, measuring approximately 39 x 39 x 107 cm or
61 x 61 x 122 cm. The live-hait trap dimensicns were 61 x
41 x 122 cm. The principal dead bait was veniscn; live bait
included roosters, guinea fowl, and quail.
Captured animals were simultaneously injected
intramuscularly with an anesthetic, ketamine hydrochloride
(Vetalar--Parke, Davis, and Company, Eetroit, MI) and a
salivation depressant, atropine sulfate (Centaur Company,
Caarlctte, NC). The ketamine hydrochlcride and atropine
sulfate were administered at dosage rates of 11 mj/kg and
0.05 mq/kq body weight, respectively. Induction time was
approximately 4-5 minutes.
immobilized animals were sexed, weighed,. ad measured
(Appendices A and B). Gray foxes and botcats were fitted
with radic-telemetry ccilars (Telcnics, Inc., Yesa, AZ, and
MEIBODS
Field Ccllection
Trapping of gray foxes and bobcats was conducted on the
Welaka Ueserve during January-March 1980, July-December
1980, January-March 1981, and January 1982 (post-study).
Custom-made and commercially available box-type live traps
were used to capture all animals. Twc models ot dead-bait
traps were used, measuring approximately 39 x 39 x 107 cm or
61 x 61 x 122 cm. The live-hait trap dimensicns were 61 x
41 x 122 cm. The principal dead bait was veniscn; live bait
included roosters, guinea fowl, and quail.
Captured animals were simultaneously injected
intramuscularly with an anesthetic, ketamine hydrochloride
(Vetalar--Parke, Davis, and Company, Eetroit, MI) and a
salivation depressant, atropine sulfate (Centaur Company,
Caarlctte, NC). The ketamine hydrochlcride and atropine
sulfate were administered at dosage rates of 11 mj/kg and
0.05 mq/kq body weight, respectively. Induction time was
approximately 4-5 minutes.
immobilized animals were sexed, weighed,. ad measured
(Appendices A and B). Gray foxes and botcats were fitted
with radic-telemetry ccilars (Telcnics, Inc., Yesa, AZ, and
Wildlife Materials, Inc., Carbondale, IL); the transmitter
frequencies were between 150-152 megahertz (MHz), with pulse
rates of 45-60 per minute. The right ear of each animal was
tattooed with an identifying alpha-numeric code. Prior to
release, all anesthetized animals were returned to the traps
until they had regained their equilibrium, which usually
occurred within 1 1/2 hours pcst-injection.
Radio-coliared animals of both species were initially
located at intervals of 4 hours during at least 1 continuous
24-hour period per week. Beginning in August 1981, selected
gray foxes and bobcats were clcated at hourly intervals for
either an 8- or 24-hour period each week. Gray Loxes, which
were principally inactive between 0ECC-1600 hours, could be
monitored for a 24-hour period by clcating them hourly for
8-hour periods between 0000-0800 hours and between 1600-0000
hours. Bobcats, which were mcre active than gray foxes
during the day, were located every hour during the 24-hcur
(OCOO-0COC hours) monitoring periods. Each radio-collared
animal that was not monitored at hourly intervals during a
particular week was located a minimum of 2-3 times that week
to detect any large shifts in its pcsiticn and to verify the
runctioninj of its transmitter.
A trucx-mounted, omni-directional whip antenna was used
to detect the general lccaticn of the radio-ccilared
animals. A 3-element, hand-held yagi antenna vas tnen used
to determine the animal's sypcific location Ly nQans ci
triangulaticn procedures (CcchraL 1580). Radio-location
readings were taken at distances of
and of <0.4 km for bobcats; consistently close approaches
were possible due to the extensive network of reads, trails,
and firelanes. The maximum location error was approximately
1 ha for foxes and 3 ha for bobcats. Each animal location
was plotted on a plastic acetate sheet, overlaid on aerial
photos. Fox and bobcat locations were plotted at photo
scales of 1:7,920 and 1:15,84C, respectively. The date,
time, habitat, weather condition, and animal activity were
recorded for each located animal. Ilctted information was
later converted to x and y coordinates by the use of a
plastic acetate grid-sheet overlaid on the aerial photos.
aadio-lccations were divided into daytime (sunrise to
sunset) and nig4ttime Iccaticns (sunset to sunrise).
Data Analy sis
The home ranges cf gray foxes and bobcats uere
calculated using 3 methcds. Ihe first was the minimum area
method, in whicn a line was drawn connecting the utmost
points of a location distriiuticn (fchr 1I97). The second
method was a modified form of the atypical habitat
elimination technique preferredd Labitat method), in which
the amount cf preferred habitat within each arinal's home
range was calculated (Ailes 1969). ILe third ootLed was the
harmonic mean measure or animal activity areas based on the
harmonic mean of an areal distribution, which used isolines
that were correlated with areas of equal activity (Dixon and
Chapman 1980). The isoline that encompassed 951 of the
radio-locations was considered as the hoce-range boundary.
Isoline intervals were set at 200 m for the gray fox
analysis and at 200 m and 600 m for the bobcat core analysis
and home range analysis, respectively. Open water that
occurred within home ranges was not included in the
calculations of home rage size.
Home ranqe overlap (using the mirimum area and harmonic
mean methods) was measured by calculating 2 values: average
percentage overlap and percentage of radio-locations within
the overlap area. Areas cf greatest activity (care areas)
and centers or activity were determined by utilizing
harmonic mean calculations. The core area boundary was
subjectively defined as the isoline that encompassed >55% c
the radio-locations for a particular individual (Anderscn
1982). The centers of activity were considered equivalent
to the harmonic mean center.
Daily activity patterns were analyzed by grouping the
locations into 2-hour intervals and then deterzizing the
percentage c locations with activity within each 2-hour
interval. lurae distance measures were calculated in
evaluating daily movement patterns: between cest arcas;
forajinj radius; and total daily acvement. Eethen rest
areas was defined as tne distance between tne rest area or
one day and that of the the next aay. Foxes citen departed
and returned to the same rest area. Foraging radius
(calculated only for foxes) was the average distance from
the daytime rest area to each of the subsequent nighttime
locations. Total daily movement was the sum of the
distances between successive locations tarcughout a 24-hour
period. Cnly days for which 6 cr mcre locations per
individual existed were used in tne calculations of the
distance measures.
Gray fox movements were also divided into 3, 4-month
seasons based on information from this and other studies
(Layne and ZcKeon 1956, Sullivan 1956, Wocd 1956, Lord 1961,
Follman 1S73). These seasons were designated as the
breeding season (December-March) ; the denning and helping
season (April-July); and the independence of the young
(August-November). Movement data were analyzed using
analysis or variance procedures (General Linear Models
Procedures-GLM) and Duncan's [ultiple range test from the
Statistical Analysis System (Helwig and Council 1979).
Habitat was divided into 8 overstoiy types and 3
understcry types. 'ie cverstcry types were bcttcmland
hardwoods, live oak harrmocks, live cak scrut (jiyrcus
vir~iniana var. eminata) Icrgleat pine-turkey oak
sandhills, meadows and open areas, mixed wccds, pine
riatwcods, and pine plantaticns (Venc 1976, SchuLtz 1979).
The understory types were open, medium, and dense, as
determined by subjective visual observation. The proportion
of different overstory and understory habitats were
calculated from the aerial-phcto overlays that included all
of the home ranges of the radio-ccllared animals. The
distribution of the radio locations in various habitats was
assumed to reflect the proportionate use of those habitats
by both gray foxes and bobcats. Chi-square analyses were
employed to determine if gray foxes and bobcats used the
various habitats in propcrticn to their availability for the
following categories: total-overstory; day-cverstcry;
night-overstory; total-understory; day-understcry; and
niqnt-understory. If the chi-square tests were significant,
simultaneous estimation procedures, developed by Neu et al.
(1974), were used to determine which habitats were preferred
or avoided. Because simultaneous estimates were performed,
a procatility level of 0.1 was used to prevent individual
ccnzidence interval errors (Neu et al. 1S74).
RESULTS
Gray Foxs
Fourteen gray foxes (8 males and 6 females) were
captured 29 times in 1,624 trap-nights during the periods
September 1980-March 1981 and January 1982. Three male and
3 female gray foxes were fitted with radic-collars.
The 6 radio-ccllared gray foxes were clcated 869 times
from December 5, 1980-December 31, 1S81. Five cf tae 6
animals accounted tor 865 (>99X) ot the locations (Table 1);
55 (6%) of these locations were ccnfirmed visually. Giv-
hundred thirty-Aive (61E) cf the locations were recorded
during the day and 334 (30i) at night.
A population estimate cf 1.0 yray foxes per kma for tne
winter cf 1391 was derived frcm mark-recapture data
(Schnabel estimate) and radio-telemetry information. The
population probably increased during the summer and fall due
to the addition of ycung animals.
Homq Range Size.--Caiculated home ranges or 5 gray
foxes (2 males and 3 famalts) averaged 400 ha using the
minimum area motacd, 360 "a usinq the ureierred aatitat
RESULTS
Gray Foxs
Fourteen gray foxes (8 males and 6 females) were
captured 29 times in 1,624 trap-nights during the periods
September 1980-March 1981 and January 1982. Three male and
3 female gray foxes were fitted with radic-collars.
The 6 radio-ccllared gray foxes were clcated 869 times
from December 5, 1980-December 31, 1S81. Five cf tae 6
animals accounted tor 865 (>99X) ot the locations (Table 1);
55 (6%) of these locations were ccnfirmed visually. Giv-
hundred thirty-Aive (61E) cf the locations were recorded
during the day and 334 (30i) at night.
A population estimate cf 1.0 yray foxes per kma for tne
winter cf 1391 was derived frcm mark-recapture data
(Schnabel estimate) and radio-telemetry information. The
population probably increased during the summer and fall due
to the addition of ycung animals.
Homq Range Size.--Caiculated home ranges or 5 gray
foxes (2 males and 3 famalts) averaged 400 ha using the
minimum area motacd, 360 "a usinq the ureierred aatitat
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method, and 532 ha using tae harmcnic mean method (Tatle 1,
Fig. 2). Ncne of the methods yielded a significant
difference (P>0.05) in home range size between sexes.
Core Area Size.--Gray foxes did not use all portions of
their home ranges with equal frequencyy (Fig. 3). Instead,
their activities were concentrated in certain areas within
taeir hcme ranges (core areas). These core areas probably
contained the most favored resting places, and possibly the
best foraging areas (Jewell 1966, Ever 1968). Sizes of the
core areas ranged from 39-190 ha with a mean of 32 ha.
These areas averaged only 16X of the total hame ranje size
but yielded 57-76% of the radio-locations (Tatil 2).
Hoze -anne and Core Area Cverlar.--CverlaF amcog acme
ranges was variable due to the tendency of gray roxes tc
establish family home ranges (Lord 1961). Degree of overlap
between males and females depended cn their relationship
(dated cr not mated). Mated pairs had the greatest average
area overlap (64, and 60'f) irrespective cf tae acse range
method whereas nou-mated anildis had less area overlap (6/
and 35X) (iabie 3). Tae single male-male ccmbinaticn was
variable defending on the method cf cvorlap calculation (19f
and 567%). female-remsal area over lap was generally lcw (<1
ani 11 ) .
Fig. 2. Home ranges of 2 males and 3 female gray foxes,
defined by the harmonic mean method, Welaka Study Area,
Florida, 1980-1981. The harmonic mean center is
represented by the black dot within each home range.
The center is identical for foxes GFI and GM4.
14
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40
30
U -
20
10 10
Y 0
Fig. 3. Three-dimensional representation of the home
range of a female gray fox (GF3), illustrating
differential use of areas within the home range
defined by the minimum area method. Each individual
grid square equals 1 ha.
r1
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Overlap among core areas was variable. One mated pair
(GF1 and GM4) had nearly identical core areas and centers of
activities, whereas the other mated pair (GF3 and GM6) had
widely separated core areas (Iig. 4). This latter
difference occurred because the hcam ranges of GF3 and GM6
also were separate (not a mated pair) until the last 2
months cf the study after which time they were found
together consistently, and considered a mated pair. Slight
overlap of core areas existed for some ncn-mated animals and
for males; however, a review of simultaneous radio-location
data showed that the overlap was spatial and not temporal in
nature. There was no overlap of core areas among females.
Activity Patterns.--Gray foxes were predictaLjy active
at night and sedentary during the day. Activity commenced
shortly before sunset, peaked between 2000-C4CO hours, and
decreased shortly after sunrise. Lhe animals were
essentially sedentary between 110C-1500 hours (Fig. 5).
Activity patterns paralleled the changing periods of
daylight throughout the year. There was no notable
difference between the overall activity patterns at males
and females.
Fig. 4. Core areas of 2 male and 3 female gray foxes,
Welaka Study Area, Florida, 1980-1981. The black dot
within each core area represents the harmonic mean
center.
A.1.A13LV
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Daily Movement Patterns.--The daily movement patterns
or gray foxes were repetitive. They traversed a large
portion of their home range each night and often returned to
approximately tie same rest area from whica they departed.
The average distance between rest areas was 426 m; the
average tcraging radius was 779 m; and the average total
daily mcvement was 3179 m (Table 4). There was no
significant difference in daily movements of males and
females (P>0.05).
Daily movements of foxes differed among seasons (Table
5). All movements (between rest areas, foraging radius, and
total daily movement) were lowest during the denning and
wuilping season (April-July) and greatest during the
breeding season (December-March). Ictal daily micvement was
the only variable that was significantly different (P<0.05)
daong all 3 seasons, being lowest during the denying and
helping season (mean=2235 m) and highest during the
breeding season (mean=8242 i).
Habitat Use.--Gray foxes did not use either overstory
or understory habitats in prcFcrticn to their availability
(=<0.01). Moreover, they utilized different habitats during
the daytime and nighttime (Figs. 6 and 7). Ecxes usually
remiainec in areas with d~nse understories, such as pine
flatwoods and live cak scrub, durlrg tae day and moved
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into more open areas, such as longleaf pine-turkey oak
sandhills and meadows, at night (Figs. 8 and 9).
Simultaneous estimation procedures (Neu et al. 1974)
supported the initial findings that fcxes preferred dense
habitats, suca as pine flatwccds and live oak scrub, during
the daytime (P<0.1), and open habitats, such as meadows and
lougleaf pine-turkey oak sandhills, at night (P<0.1)(Tables
6 and 7). Furthermore, irrespective of the time of day,
foxes avoided bottomland hardwoods and live cak aammccks and
preferred live oak scrub. Cther habitats were either
avoided or showed non-significant use.
Bobcats
Seven bobcats (4 males and 3 females) were captured 21
times in 2,657 trap nights. Six animals (3 maies and 3
tamales) erre fitted with radio-cellars.
The 6 collared bobcats were located 294 times from
February 15, 1980-Decemfer 31, 1981. Two males (BM2 and
314) accounted for 269 (925) of the bobcit radic-locations.
Three of tie animals radio-ccllared during January-June,
1980 (Table 8), were lost from the study due tc
radio-ialtunctions or deaths. Cne hundred seventy-nine
radio-locations (b1%) were recorded during the day and 115
(39.) at nijiht.
60
PFf 50
40
20
Fig. 8. Daytime habitat use by a female gray fox (GFl),
Welaka Study Area, Florida, 1980-1981. Habitats are
pine flatwoods with a dense understory (PFLT/DNS) and
longleaf pine-turkey oak sandhills with an open understory
(LPTO/OPN). The broken black line is the boundary between
the habitats. The arrows point to extremes in location
frequencies. One grid square equals 1 ha.
30 p
050
40
% s o
20
Fig. 9. Nighttime habitat use of female gray fox
(GF1), Welaka Study Area, Florida, 1980-1981.
(See Fig. 8 for explanation of symbols.)
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A population estimate cf 0.52 totcats per kma was
calculated from trapping, radio-isotope tagging, and
radio-telemetry data before an apparent die-cft probablyy
due to disease) occurred in June 1960, after which time the
population density decreased (Ccnner 1982).
Homeg angel Size.--Home ranges of the 2 male bobcats
averaged 4438 ha using the minimum area method, 3350 ha
using the preferred habitat method, and 3820 ha using the
harmonic mean method (Fig. 10). These 2 animals had an
average hcme range overlap of 101 and 8%, based oa the
minimum area and harmonic mean methods, respectively (Table
8).
Bobcats, like the gray ioxes, visited different
pcrticns of their acme ranges with varying r requency (Fig.
11). Their core areas, however, were act as distinct as
those of tne gray foxes. Tae mean core area ct the 2 male
individuals was 909 aa (range=695-1124 ha), whicn accounted
for an average of 24 ct their hcme range size and an
average or 59% the total radic-locations. No overlap was
determined icr core areas between ancials (Fig. 10).
Fig. 10. Home ranges and core areas of 2 male bobcats,
defined by the harmonic mean method, Welaka Study Area,
Florida, 1980-1981. The core areas are delineated by
the dotted lines within each home range. The harmonic
mean center is represented by the black dot within each
home range.
z
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50 22
25
0
0
Fig. 11. Three-dimensional representation of the home
range of a male bobcat (BM4), illustrating differential
use of areas within the home range. The bold black
line is the home range boundary defined by the minimum
area method. Each individual grid square equals 4 ha.
Activity Patterns.--Most botcat activity occurred at
nig.t; however, bobcat nighttime activity was more erratic
than that ot the gray fox. Activity began to increase
before sunset, with peaks between 18GC-2000 and 2200-0000
hours, decreased to a nighttime low between 0200-0400 hours,
and then increased about sunrise. Eocat activity was
recorded during all periods of the 24-hour day (Fig. 12).
Daily Movement Patterns.--The daily movement patterns
or the tobcat were nomadic within their hcme range;
movements of varying distances occurred at any time ot the
day or night. The 2 male ottcats had a mean distance
between rest areas ot 2700 w (range=0-4245 m, SE=543 m) with
an average total daily mcvement ot 6090 m (range=412-9631 m,
SE=1027 m).
Habitat Use.--Bobcats did not use either overstory or
understory habitats in propcrtica tc their availability
(0<0.01). They used habitats with dense or medium
unaerstcries and avoided naaitats witA cpen understories.
Moreover, tae bobcats utilized different habitats during the
day than at night, although these differences were not as
distinct as those of the gray fox (Fiqs. 13 and 14).
r'-
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Simultaneous estimation procedures (Neu et al. 1974)
indicated that bobcats preferred hottcaland hardwoods hcth
day and night, with some preference toward pine flatvcods
during the day (P<0.1) ablee 9). Ihey avoided areas with
open understories, such as meadows and longleaf pine-turkey
oak sandhills, during the day, and traveled in habitats with
medium understories at night (P<0.1) (lable 10). TMeir use
of the ether habitats was net different from availability
(P>0.1) .
11
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DISCUSSION
Gral Fox
Home Range Variability.--The mean home ranges of gray
foxes reported in this study (males=602 ha, females=365 ha)
were substantially larger than these reported from other
regions of the United States, except for Misscuri (676 ha)
(Table 11). Although differences in sizes cf home ranges
may be attributed to a number of ractcrs, differences among
habitats, which affect prey distribution and abundance, and
i: turn, rox density (Wood et al. 1958, Trani 1980),
probaiby constitute the singlemcst important variable in
detrmininiq hcme range size cr gray fcxes. The gray fox is
omnivorous; its annual diet is ccaprised primarily of
vertebrates (50) vegetaticn--imotly fruit (15A), and
arthropcds (35s) (Yoho and Henry 1972, Trapp 1973, Trani
1980). Open habitats provide areas in which gray foxes
forage for food. Habitats with dense understcries are
important as daytime rest areas but are poor reservoirs of
food supplies. Home ranges of gray cfxes were larger where
habitats were more homogeneous (Harcldscn 1982, this study)
than where taey were more disjunct and interspersed (Trapp
1973, Hallerg 1974, Fuiler 1978, Yearsley and Samuel 198C).
DISCUSSION
Gral Fox
Home Range Variability.--The mean home ranges of gray
foxes reported in this study (males=602 ha, females=365 ha)
were substantially larger than these reported from other
regions of the United States, except for Misscuri (676 ha)
(Table 11). Although differences in sizes cf home ranges
may be attributed to a number of ractcrs, differences among
habitats, which affect prey distribution and abundance, and
i: turn, rox density (Wood et al. 1958, Trani 1980),
probaiby constitute the singlemcst important variable in
detrmininiq hcme range size cr gray fcxes. The gray fox is
omnivorous; its annual diet is ccaprised primarily of
vertebrates (50) vegetaticn--imotly fruit (15A), and
arthropcds (35s) (Yoho and Henry 1972, Trapp 1973, Trani
1980). Open habitats provide areas in which gray foxes
forage for food. Habitats with dense understcries are
important as daytime rest areas but are poor reservoirs of
food supplies. Home ranges of gray cfxes were larger where
habitats were more homogeneous (Harcldscn 1982, this study)
than where taey were more disjunct and interspersed (Trapp
1973, Hallerg 1974, Fuiler 1978, Yearsley and Samuel 198C).
44
ro
a mm
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This relationship between hcme range size and habitat
heterogeneity was apparent also cn the Welaka Study Area.
Home ranges containing tae smallest proportion cf
homogeneous dense forested areas (GF1, GF4, GM4) were
smallest (136-293 ha), whereas these with the greatest
proportion of uniform dense crested areas (G53 and Gi6)
were largest (667 and 917 ha). Therreore, cptiaum fcx
habitat is characterized by an interspersicn ct dense
habitats for daytime resting and cpen areas for nighttime
foraging. Intuitively, the proportion cf foraging habitat
should invariably exceed that of resting habitat.
Daily joveentjs.--Foxes were principally nccturnal but
exhibited some crepuscular and early morning activity.
Their activity during the twilight and early daytime hours
may add an important feature to their niche hy allowing their
to oxplcit diurnally-active prey species, such as lizards
and certain small mammals (Trapp 1973). Daily movement
patterns were similar for males and females Lut varied
seasonally. Movement was greatest during the breeding
season. TIese Aindings were similar to these ct Trapp
(1973) in Utah, and Fcilman (1973) in Illiicis, sno reported
that gray foxes moved greater distances in winter (mating)
than summer (denning). Restricted movements Ly foxes in
summer are attributable tc the dependence cf young and the
ready availability cf food (fruits and insects). :n winter,
juveniles are dispersing frox their natal home ranges,
adults may be moving to find mates, ana food may be more
difficult to obtain.
Bobcats
Home Range Variability.--The reported mean size of
bobcat home ranges has varied considerably, from 97 ha tor
female bobcats in Louisiana (Hall and Newsom 1976) to 620C
ha for male bobcats in northern Minnesota (Eerg 1981) (Table
12). Male chme ranges are consistently 2 tc 3 times larger
taan thcse of females. Although sales have identifiablE
core areas, they travel more throughout their hCme ranges
than females (Kitchings and Story 1981).
Home ranges are consistently larger in the northern and
western portions of tne country than in the South (Table
12). This geographical variation in home range size may be
a function of the climate, which, in turn, affects the
variety and abundance of prey. Bobcats are exclusively
carnivorous, leading primarily on mammalian prey (Progulske
1955, Buttrey 1974, Fritts and Seaiander 1978, Guenther
1580). Ihe warn southern regions probably nave a more
consistent year-round prey base thaL the more northern and
western sections of the country.
C,
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ow
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am
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48
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002
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(0 C CC C
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The average home range of the bobcats monitored in this
study was much larger than tncse previously reported from
the southern United States, except for lennessee (Kitchings
and Story 1981). These researchers maintained that the
difference between their study area and the other southern
study sites was probably the richness of the prey base,
waich was related to the prevalence of early successional
fields (old fields). Buie et al. (1981) noted that the
decrease in old field sites may have caused the expansion of
bobcat hcme ranges cn the Savannah Fiver Plant during the
past 20 years. In this study, the reasons for large home
ranges may be two-fcld. First, the number of small mammals
may be relatively low due to the dominance cf homogeneous
dense forested habitats. Seccndly, the apparent die-cfi of
the resident bobcats during the summer of 1980 may have
created vacant habitat into which surviving bctcats expanded
their home ranges. Initial data, based cn trapping and
limited radio-telemetry, showed that the original resident
female bobcats on the Welaka Reserve occupied smaller home
ranges (2CO-1000 ha) than those determined tor the 2 males
(B32 and B34) carter the die-off. Similar range expansions
following bobcat deaths have been reported by Miller (1980)
and LeAbeck and Gculd (1981). Therefcre, qecgrapnicai
variation in home range size of boccats is probably a
function of both habitat and climate, which, in turn affects
the prey base; however, Iccalized factors, such as disease
and exploitation pressure also play a role in affecting home
range size.
Daily Movements.-- Bobcats were principally nocturnal
but were found to be active at any time during the day.
Occasionally they were active all night, but often they had
movement lulls between 00CC-C400 hours. This pattern of
activity is consistent with that reported for bbccats in
south Florida (Guenther 1980) and in Alabama (Miller 1980).
The bobcat activity cycle usually matches that of its prey,
such as cottontail rabbits (Sylvilaqus iloridanus) (Lord
1964) and deer (Odocoileus viriLnianus) (Halls 1978).
Gral Fox and Ectcat Interacticns
The canids and the telids have had a lcng, separate
evolutionary history (Kleiman and Eisenbery 1973). The
feeding and hunting behavior of the canids (omnivorous and
prey chasing) has encouraged a social existence. The basic
social structure consists of a long-lived pair tond in which
the male becomes involved in the rearing of the young. The
pair bend of the gray fcx is year-rcund.
51
The feeding and hunting behavior cf most felids
(exclusively carnivorous with ambush attack of their prey)
has encouraged the development of a social system consisting
of nearly exclusive home ranges (especially between like
sexes) and a solitary existence (Kleiman and Eisenberg
1973). The pair bond of the bobcat generally lasts only
through the breeding season, with the responsibility of
raising the young falling entirely to the female (Bailey
1974).
In this study, differences in gray rcx and bobcat
movements and behavior may have prevented competition
between the species. The nome ranges of male bobcats (3820
ha) were 6-7 times larger than those cf gray foxes (582 ha).
Furthermore, these 2 species had ncticeatle differences in
habitat selection. Bobcats preferred dense bcttomland
hardwood habitats during all portions of the day and night,
and generally avoided open wooded areas, suca as longleaf
pine-turkey oak sandhills. Gray foxes, however, avoided
bottomland hardwood habitats and preferred cpen areas such
as longleaf pine-turkey oak sandhills at night. The single
habitat that was preferred by both species was the dense
pine fiatwcods which was prohbaly used as daytime retreats.
However, due to the prevalence of this type of habitat on
tae study area, it is unlikely that competiticL for pine
flatwcod sites occurred. It is cpssible that the bobcats
precluded the gray toxes iron the bcttomland sites; however,
on the Welaka Reserve where the bobcats visited only
sporadically, gral roxes still avoided bottcmland hardwoods.
Foraging Vabits cf bobcats and gray foxes are similar
during certain periods of the year. Although gray foxes
feed heavily on fruits and insects in summer, they prey
substantially on small mammals, which are also prey of
bobcats, in winter. Habitat selection by the 2 species,
however, may mitigate the potential foraging competition.
Bobcats prefer bottomland sites, which are richer in prey
than forested upland areas (Kitchings and Story 1981, M. C.
Conner and D. R. Progulske, Jr., unpublished data), whereas
gray foxes avoid bottomland habitats, preferring, instead,
upland sites.
In conclusion, although interactions between gray foxes
and bobcats may have occurred, differences in hcme range
size, habitat selection, and foraging behavior probably
prevented significant competition between these 2 species on
the Welaka Study Area.
MANAGEMENT IMPLICATICNS
Differences in social structure and movements of gray
foxes and bobcats place the species at opposite ends of the
management spectrum. Although both species can be managed
through adjustments in harvest'regulations, it is feasible
to manage gray foxes, but probably not bobcats through
habitat manipulation.
Gray foxes are short-lived omnivcres with definable
naoitat requirements and relatively small hcme ranges.
Consequently, it is possible tc manage for this species
through habitat manipulation coupled with harvest
regulation. Optimum fox habitat has an interspersion of
dense areas for daytime retreats and open areas for
nighttime fcraqing. These habitat tracts shcuid be mixed in
relatively small patches ci 5-15 ha (Lased on a mean home
range size of 300-500 ha) to support the greatest numbers of
animals.
Bobcats are solitary, wide-ranging, and Icng-lived
carnivores. Although habitat preferences cf bbccats can be
identified, tae management of habitats cn the large tracts
of land needed to achieve optixua population levels would
be, in most instances, financially and Icgistically
54
impractical. The most etticient way to manage botcat
populations is probably through pcEulaticn monitoring
programs, such as scent-statica surveys, coupled with the
manipulation of harvest. However, it a decision were made
to manage habitats for bobcats, the preservation oc
bottomland hardwoods would be a critically important
strategy.
LITEiATURE CIiTE
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vulpes). J. mammal. 50:1C8-12C.
Anderson, D. J. 1982. The home range: a new ncnparametric
estimation technique. Ecology. 63:103-112.
Bailey, I. N. 1974. Social organization in a bchcat
population. J. iildl. Manage. 3E:435-466.
Berg, W. E. 1981. Ecology of bobcats in northern Minnesota.
Pages 55-61 in Bobcat research conference proceedings:
current research on biology and management of Ljnx
rufus. Natl. Will. Fed. Sci. and Tech. Ser. 6.
Buie, D. E., I. T. Fendley, and H. F cNab. 1981. Fall and
winter home ranges of adult bobcats on the Savannah
River Plant, South Carolina. Pages 42-46 in Bobcat
research conference proceedings: current research on
biclogy and management to Lynx rutus. Natl. Will. Fed.
Sci. and Tech. Ser. 6.
Buttrey, G. W. 1974. Fcod habits and distribution of tne
bobcat, Lynx rufus rutus (Schreber), on the Catoosa
wildlife Manaqement Area. M.S. Thesis. Tennessee Tech.
Univ., Cookeville. 64 Fp.
Carey, A. B. 1982. The ecology of red foxes, gray ioxes, and
rabies in the eastern United States. Wild. Soc. Bull.
10: 1-26.
Cochran, W. W. 1980. Wildlife telemetry. Pages 507-520 in
S. S. Schemnitz, ed. wildlife management techniques
manual, 4th ed. The Wildl. Scc., Washingtcn, D.C.
Conner, M. C. 1982. Determination of bobcat (1ynx rutus)
and raccoou (rocycn Ictor) population abundance by
radio-isotope tagging. M. S. Thesis. Univ. of Florida,
Gainesville. 55 pp.
Crowe, E. M. 1972. The presence of annuli in bobcat tooth
cementum layers. J. Aildl. Manage. 36:1330-1332.
1975. Aspects oa ageing, growth, and reproduction cf
bobcats froa Wyoming. J. Mammal. 56:177-198.
Department of the Interior. 1982. Expcrt of bobcat taken in
tne 1981-1982 season. Fed. Reqist. 47:1294.
Dixon, K. R., and J. 2. Chapman. 1980. Harmonic mean measure
of animal activity areas. Ecclcgy 61:1040-1044.
Ewer, R. F. 1968. Ethology of mammals. Plenum Eress, New
York, L.Y. 418 pp.
Follman, E. H. 1973. Comparative ecology and behavior of red
and gray foxes. Ph.D. Thesis. Southern Illinois Univ.,
Carbondale. 152 pp.
Fritts, S. H., and J. A. Sealander. 1978. Diets of bobcats
in Arkansas with special reference to age and sex
differences. J. Wildly. Manage. 42:533-539.
Fuller, T. D. 1978. Variable hcme-range sizes o female gray
foxes. J. Mammal. 59:446-449.
Guenther, D. D. 1980. Home range, social organization, and
movement patterns of the bctcat, _Lynx rufus, from
spring to fall in south-central Florida. M.S. Thesis.
Univ. South Florida, Tampa. 66 pp.
Hall, H. T., and J. D. Neusom. 1976. Summer hcme ranges and
movements of bobcats in hottcaland hardwoods of
southern Louisiana. Proc. Southeast. Assoc. Game and
Fish Comm. 30:427-436.
laillberg, D. L. 1974. A contribution toward the better
understanding of gray fox (Uro1cn cinereoargenteus)
temporal and spatial natural history. M.S. Thesis.
California. State Univ., Sacramentc. 280 pp.
Halls, I. K. 1978. White-tailed deer. Pages 43-65 in J. L.
Schmidt and D. L. Gilbert, eds. fig game or North
America. Stackpole Bcoks, Harristurg, Pa.
Haroldscn, K. J. 1982. Habitat ecology of the gray fox in
the czark highland. M.S. Thesis. Univ. Missouri,
Columbia. 99 pp.
Helwig, J. I., and K. A. Council. 1979. SAS users' guide.
1979 edition. SAS Inst. Inc., Cary, N.C. 494 pp.
Jennings, 1. L., N. J. Schneider, A. I. Lewis, and J. E.
Scatterday. 1960. Fox rabies in Flcrida. J. Wildl.
Manage. 24:171-179.
Jewell, P. A. 1966. The concept of home range in mammals.
Symp. Zool. Soc. London. 16:85-1C9.
Kitchings, J. T., and J. E. Story. 1981. Home range and diet
of bobcats in eastern Tennessee. Pages 47-52 in Bobcat
research conference proceedings: current research on
biolgcqy and management of Lynx rufus. Natl. Widl. Fed.
Sci. and Tech. Ser. 6.
Kleiman, D. G., and J. F. Eisenberg. 1973. Comparison of
canid and telid social systems from an evolutionary
perspective. Anim. Behav. 21:637-659.
Laessle, A. M. 1942. The plant communities of the Welaka
area. Univ. Florida Bicl. Sci. Ser. 4:1-143.
Layne, J. N., and W. H. McKeon. 1956. Some aspects of red
rox and gray fox reproduction in New York. N.Y. Fish
and Game J. 3:44-74.
Lembeck, M., and G. I. Gould. 1981. Dynamics of harvested
and unaarvested bobcat populations in California. Pages
53-54 in Bobcat research conference proceedings:
current research on biology and management of Lynx
rufus. Natl. Wildl. Fed. Sci. and Tech. Ser. 6.
Lord, B. D., Jr. 1961. A population study of the gray rcx.
Am. Midl. Nat. 66:87-109.
194. Seasonal changes in the activity of penned
cottontail rabbits. Anim. Eehav. 12:38-41.
Marshall, A. D., and J. H. Jenkins. 1S66. Movements and home
ranges of bobcats as determined ty radio-tracking in
the upper coastal plain of west-central South Carolina.
Prcc. Southeast. Assoc. Game and Fish Ccmm.
20:206-214.
McLean, R. G. 1970. Wildlife rabies in the United States:
recent history and current concepts. J. Will. Dis.
6:229-235.
Miller, S. D. 1980. The ecolcgy of the bobcat in south
Alatama. Ph.D. Thesis. Auburn Univ., Auburn, Ala. 156
pp.
Monr, C. C. 1947. Table or equivalent populations of North
American snall mammals. Am. Midl. Nat. 37:223-249.
Mcnk, C. D. 1965. Southern mixed hardwood forest or
northcentral Florida. Eccl. Mcnogr. 35:335-354.
National Cceanic and Atamspheric Administraticn. 1974.
Climates of the states. Vol. 1. Eater Inf. Cent., Inc.
Port Washington, N.Y. 486 pp.
Neu, C. W., C. R. Byers, and J. M. Eeek. 1974. A technique
for analysis of utilization-availability data. J.
Wildl. Manage. 38:541-545.
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ratios in fur animals. Am. Midl. Nat. 43:355-382.
Progulske, D. R. 1955. Game animals utilized as food by the
bobcat in the southern Appalacnians. J. Wild. Manage.
19:249-253.
Provost, E. E., C. A. Nelson, and A. E. Marshall. 1973.
Population dynamics and behavior in the bobcat. Pages
42-67 in R. L. Eatci, ed. The World's Cats, Vol. I,
ecclogy and conservation. worldd Wildi. Safari,
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Root, D. A. 1981. Productivity and mortality of gray foxes
and raccoons in southwestern Wisconsin. F.S. Thesis.
Univ. Wisconsin, Stevens Pcint. 106 pp.
Schultz, D. 1979. Timber :and soil type map of the Research
and Education Center, Welaka, Florida. Inst. of Food
and Agric. Sci., Univ. Florida, Gainesville. 122 pp.
Mirec.
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1980-1981. Florida Game and Freshwater Fish Comm. 7
pp. Mimeo.
Sullivan, E. G. 1956. Gray tox reproduction, denning, range,
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Trani, 1. K. 1980. Gray fox feeding ecology in relation to
prey distribution and abundance, d.S. Thesis.
California. State Univ., Humbcldt. 89 pp.
Trapp, G. 2. 1973. Comparative behavioral ecology of two
southwest Utah carnivores: Bassariscus astutus and
Urccycn cinereoa renteus. Ph. C. Thesis. Univ.
Wisconsin, Madison. 251 pp.
_...., and D. L. Hallberg. 1975. Ecclcqy of the gray fox
(Urocyon cinereoarjenteus): a review. Pages 164-178 in
M.W. Fox, ed. The wild canids. Van Nostrand Reinhold
Co., New York, N.Y.
Vano, P. A. 1976. Successional relationships of five Florida
plant communities. Ecology 57:498-508.
Wood, J. E. 1954. Investatgation c fox populations and
sylvatic rabies in the Scutheast. Trans. North Am.
Wildl. Conf. 19:131-139.
1958. Age structure and productivity of a gray fox
population. J. Sammal. 39:74-86.
__, D. E. Davis, and E. V. Komarek. 1958. The distribution
of fox populations in relation to vegetation in
southern Georgia. Ecology 39:160-162.
Yearsley, E. F., and D. E. Samuel. 1980. Use of reclaimed
surface mines by fcxes in West Virginia. J. Wildly.
Manage. 44:729-734.
Yoho, N., and V. Henry. 1972. Foods o! the gray fox (Utrocyon
cingreoarqenteus) on European wild hog (Sus scrofa)
range in east Tennessee. J. Tennessee Acad. Sci.
47:77-78.
Zezulak, D. S., and R. G. Schwab. 1981. A comparison of
density, home range and habitat utilization of bobcat
populations at Lava Beds and Jcshua Tree National
Monuments, California. Pages 74-79 in Ectcat research
conference proceedings: current research on biology and
management of Lynx rufus. Natl. Wildl. Fed. Sci. and
lech. Ser. 6.
PART 2: SCENT-STAIION INDICES AS INDICAIOBS
OF POPULATION ABUNDANCE FCO
BCBCATS, RACCOONS, GRAY FCXES, AND CPCSSUMS
INTRCDUCTION
The use Of scent-station transects as a means of
determining seasonal and annual trends in the relative
abundance of mammalian carnivores has escalated in recent
years. Originally developed as a method for determining the
relative abundance of red (Vulpes vules) and gray foxes
(Uroc2on cinereoargenteus) (ichards and Hine 1953, Wood
1959), the technique has been applied to coyotes (Canis
latrans) (Linhart ana Knowltcn 1975, Davison 1981, Morrisca
et al. 1981), bobcats (Felis rufus) (Brady 1981, Hon 1981,
Johnson 1981, Knowlton and Tzilkowski 1981, Sumner and Bill
1980, Morrison et al. 1981), wolves (Canis lupus) (Pimlctt
et al. 1S69), and river otter (Lutra canadensis) and mink
(Mustela visou) (Humphrey and Zinn 192). Research has
focused also on standardizing and improving otth the
technique and analysis of data (Rcughtcn and Sweeny 1982).
PART 2: SCENT-STAIION INDICES AS INDICAIOBS
OF POPULATION ABUNDANCE FCO
BCBCATS, RACCOONS, GRAY FCXES, AND CPCSSUMS
INTRCDUCTION
The use Of scent-station transects as a means of
determining seasonal and annual trends in the relative
abundance of mammalian carnivores has escalated in recent
years. Originally developed as a method for determining the
relative abundance of red (Vulpes vules) and gray foxes
(Uroc2on cinereoargenteus) (ichards and Hine 1953, Wood
1959), the technique has been applied to coyotes (Canis
latrans) (Linhart ana Knowltcn 1975, Davison 1981, Morrisca
et al. 1981), bobcats (Felis rufus) (Brady 1981, Hon 1981,
Johnson 1981, Knowlton and Tzilkowski 1981, Sumner and Bill
1980, Morrison et al. 1981), wolves (Canis lupus) (Pimlctt
et al. 1S69), and river otter (Lutra canadensis) and mink
(Mustela visou) (Humphrey and Zinn 192). Research has
focused also on standardizing and improving otth the
technique and analysis of data (Rcughtcn and Sweeny 1982).
Despite widespread use of the technique (Jchnson et al.
1981), the relationship between pcpulaticn abundance and
scent-staticn indices remains unclear. To date, tae only
reported correlation between scent-station indices and
population abundance was developed for coyotes in Utah and
Idaho (Eavison 1981).
The objectives of this project were: (1) to evaluate
scent-staticn indices as indicators of seasonal and annual
trends in the abundance of bobcats, gray foxes, raccoons
(Procyon lotor) and opossums (Didelphis virginiana); and
(2) to compare tce indices with population abundance
estimates based on trapping, radioisotope tagging, and
radio-telemetry.
STUEY AEEA
All scent-station data were collected on the University
of Florida Besearch and Education Center at Welaka, Florida.
The 918-ha area is located on the east bank of the St. Johns
River in southeastern Putnam County. Annual mean
temperature and rainfall for the northeastern Florida area
are 22 C and 137 cm, respectively (Eational Cceanic and
Atmospheric Administration 1974).
The soils and plant communities of the Welaka Study Area
were described in detail by Laessle (1942), Veno (1976), and
Schultz (1979). The thick well-drained to moderately
well-drained acid sands were derived from marine sediments.
The area has little topographic variation; elevations range
from sea level in the western sector (St. Johns River) to
20 m in the eastern sector. The increasing relief, and
accompanying decrease in soil moisture, along the
west-to-east gradient gives rise to 3 major plant
communities. Bottomland hardwocds occupy 188 ha (20%) of
the study area and are found principally in the St. Johns
Eiver floodplain; pine flatwccds, primarily
Pinus elliottii var. elliottii, occupy 489 ha (531) and are
located adjacent to the floodplain forest; longleaf pine
(Pinus Lalustris)-turkey oak (uercus laevis) sandhills
occupy 115 ha (13;) and lie in the undulating eastern
portion of the area, adjacent to the pine flatwcods. In
addition, numerous marsh-like ponds, ihich occupy a total of
about 60 ha (6%) of the area, are distributed throughout the
pine flatwoods and sandhills. The remaining 8 of the area
is contained in wcrk and research facilities.
Hunting and commercial trapping have been prohibited on
the Welaka Area since the late 1930s.
METHODS
Three permanent scent-station transects were established
along trails on the Welaka Area; 2 transects were located in
pine flatwoods and 1 in longleaf fine-turkey oak sandhills.
Each transect consisted of 10 stations spaced at 0.32 km
(0.2 mi) intervals; each station consisted of a circle of
moist sifted sand 0.91 m (3 ft) in diameter with a
centrally-placed cottonuall that was saturated with bobcat
urine (Cronk's Outdoor Supplies, Wiscasset, ME). Transects
were operated for 1 night per month for the 24 months,
January 1980-December 1981. Transects were activated in the
afternoon and checked for visitation the following morning.
If rain rendered the traasects inoperative, the procedure
was repeated until an operative transect-night was achieved.
A visit was defined as the presence of 1 or more tracks
of a species per station. Visitation rates were expressed
as the percentage of stations visited by each species for
each transect night.
Analysis of variance procedures were executed cn arcsine
transformed visitation rates using the General linear Models
Procedure (GLa) of the Statistical Analysis System (SAS).
The effects of year and month were tested; the effects of
habitat could aot be tested because there was no replication
of transects in tne sandhill habitat. All statistical
analyses were performed on the transfcrmed rates; however,
in this paper, only the actual percentage visitation rates
are presented.
Population abundance estimates fcr bobcats and raccoons,
with which the scent-station indices were compared, were
derived principally from a companion study (Conner 1982).
Basically, the abundance estimates were based on the
radioisctcpe mark-and-recapture technique (bobcats and
raccoons) and traditional mark-and-recapture methodologies
based on trapping (bobcats, raccoons, gray foxes, and
opossums). Population abundance data for bobcats and gray
foxes were supplemented by radio-telemetry studies
(Proqulske 1982).
RESULTS
Bobcat Visitation
The mean monthly scent-station visitation rate for
bobcats for the 24-months was 1%. Visitaticn by bobcats
never exceeded 4% for any single month (Fig. 1). No
significant trends in bobcat visitation by year or month
were observed (P > 0.05, Table 1).
Raccoon Visitation
The mean monthly rate of scent-station visitation by
raccoons for the 24-months was 271. The visitation rate by
raccoons differed significantly between years (P < 0.01,
Table 1), being greater in 1980 (30j) than in 1981 (17%)
(Fig. 1). The combined monthly rates for the 2 years
indicated that the highest visitation rate was recorded in
September (41%), and tae lowest in Novemter (10c) (Table 2).
'BOBCAT 1980
1981 ---
,----' '---------' \
* -
I
/
\ !
"GRAY FOX A
80.0
60.0
40.0 -
20.0
0.0
I'
/ \ /
'OPOSSUM
A /
JAN MAR MAY JUL SEP NOV
MONTH
Fig. 1. Monthly scent-station visitation rates for bobcats,
raccoons, gray foxes, and opossums, Welaka Area, Florida,
1980-1981.
0.0
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Table 1. Results of analysis of variance Frocedures for arcsine
transformed scent-station visitation rates for hcfcats, raccoons,
gray foxes, and opossums, Welaka Area, Florida, 1980-1981.
Species Factor df F-value
Bobcat Year 1 0.13
Month 11 1.09
Year*Month 11 0.45
Raccoon Year 1 10.33 a/
Month 11 1.78
Year*Mcnth 11 1.S8
Gray fox Year 1 6.53 b/
Month 11 1.84
Year*Month 11 0.26
Cpossum Year 1 8.42 a/
Month 11 1.75
Year*Month 11 2.61 b/
a/P < 0.01.
b/P < 0.05.
Gray Fox Visitaticn
The mean monthly scent-station visitation rate by gray
foxes fcr the 24-months was 48%. The visitation rate by
foxes differed significantly between years (P < 0.05,
Table 1), being higher in 1981 (527) than in 1980 (35%).
The combined monthly rates for the 2 years indicated that
the highest visitation rate occurred in November (82%), and
the lowest rate in May (22%) (Table 2).
CEossum Visitation
The mean monthly scent-station visitation rate by
opossums for the 24-months was 9.9%. Although the
visitation rates by opossums differed significantly by years
(P < 0.01, Table 1), being greater in 1980 (12.5%) than in
1981 (7.3%) (Fig. 1), the significant interaction between
year and month (jP < 0.05, Table 1) nct only negated the
year-difference but alsc further statistical comparisons.
Table 2. Results of Duncan's Multiple Range Test for arcsine
transformed scent-station visitation rates by month for
raccoons and gray foxes on the Welaka Area, Florida,
1980-1981.
Raccoon Gray Fox
Month Rate (%) a/ Month Rate (%) a/
Sep 41 A Nov 82 A
Oct 33 AB Dec 70 AB
Jun 33 AB Cot 67 AB
May 31 ABC Jan 46 ABC
Feb 27 ABC Jun 44 ABC
Aug 21 ABC Feb 42 ABC
Apr 21 ABC Sep 40 ABC
Dec 19 ABC Aug 39 ABC
Mar 18 ABC Mar 35 BC
Jul 17 ABC Jul 35 BC
Jan 15 BC Apr 28 BC
Nov 10 C May 22 C
a/ The presented visitation rates (%) are actual mean
monthly rates, not arcsine transformed rates; those
rates followed by the same letter are not
significantly different f( > 0.05)-
DISCUSSION
Determination of the relationship between scent-station
indices and population abundance is an essential step in
determining the sensitivity of the indices to changes in
abundance. Scent-station indices can detect area-wide
changes in abundance, changes in habitat use, and seasonal
trends in population abundance.
Although the monthly scent-station visitation rate for
bobcats was low throughout the 24-mcnth period (Fig. 1),
trends in the visitation rate were substantiated by
estimates of population abundance and by scat-count indices.
During the 5-month period, January-May 1980, the population
density of bobcats on the study area was estimated at 5
animals (0.52 per km2), the scat-count index was 0.17 scats
per km of trail (Conner 1982), and the scent-station
visitation rate was 1.3%. During the following 16 months,
June 190E-September 1981, the density of bobcats was
substantially lower. In June 1980, 3 of the 5 bobcats on
the area died or disappeared, and only 2 animals were known
to have visited the area periodically from June
1980-September 1981 (Progulske 19S2). Concurrently, the
scent-station visitation rates and scat-count index were
markedly lower, 0.44X and 0.02 scats per km, respectively.
During the 3-month period, Cctober-recember 1981, the bobcat
population density increased as indicated by frequent
observations of unmarked animals and by the capture of an
unmarked male. Similarly, the scent-station visitation rate
and scat count index rose to their highest levels, 1.5% and
0.20 scats per ks, respectively. Thus, both increases and
decreases in bobcat population abundance were reflected by
scent-station indices.
The population density of racccns on the study site was
estimated at 95-105 animals (10.3-11.4 per kmz) during the
winter period, January-March 1981 (Conner 1982). The rate
of scent-station visitation for tais population was 14%
during the same time interval. This 14% visitation rate,
however, was substantially less than the 32% rate for the
January-March period of 1980. The difference in rates
between years may have resulted from rainfall patterns;
below normal rainfall occurred throughout the 2nd half of
1980 and all of 1981. Consequently, in 1981, wetland
habitats cn the study area were diminished in tctal area and
restricted in distribution to the bcttomland hardwoods and
upland ponds, neither of which were mcnitored directly by
scent-staticn transects. The combined effects of the
disproportionate use by raccocas of wetland over upland
habitats on the Welaka Area (Conner 1982), the limited
availability of wetlands in 1981, and the skewed upland
distribution of scent-station transects resulted in
decreased scent-station visitation by raccoons from 1980 to
1981. Sumner and Hill (198C) also noted decreased
visitation of upland scent-station transects by raccoons
when the aniamls were seasonally concentrated in wetland
habitats. Thus, scent-station transects appeared to not
only reflect changes in raccoon abundance, but also shifts
in habitat use.
The population density of gray foxes on the Welaka Area
and surrounding lands was estimated at 1 per km2 during the
winter period, December 1980-March 1981 (Progulske 1982).
Tae corresponding scent-staticn visitation rate for this
breeding population was 56%. During the next 2 seasons,
April-July and August-November 1981, scent-station
visitation rates were 45% and 65%, respectively. The
April-July period, during which scent-staticn visitation was
lowest, corresponded to the season of denning and rearing of
young, a period when tue adult fox population was at its
annual low and total daily acvements (2235 m) were minimal
(Progulske 1982). The subsequent peak in scent-station
visitation during the late-summer and fall season resulted
from an increase in population density due to the addition
of young, dispersal of juvenile foxes, and accelerated daily
movements of adults (4385 m) (Progulske 1982). However,
there were no significant differences among visitation rates
for these periods (P > 0.05).
Gray fox scent-station visitation rates were affected by
both population density and movements; however, population
density was probably the more important factor. To
illustrate, during the December 1S80-March 1981 breeding
period, total daily movements (8242 m) were nearly double
that of any other period (Prcgulske 1982); however,
scent-station visitation was intermediate during this same
period. Population abundance also was very likely
intermediate during the December-March period because both
juvenile dispersal had ended and over-winter mortality had
occurred. Therefore, scent-station indices for gray foxes
accurately reflected seasonal trends in population density,
despite seasonal changes in movement patterns.
Opossum population density, based on 166 captures of 60
individuals, was 10.1 per km2 during December 1980-March
1981. The scent-staticn visitation rate during this period
was 7.5%. The seemingly erratic trends in scent-station
visitation rates by opossums (Fig. 1), as well as the
significant interaction between year and month (Table 1),
indicated that scent-station indices probably did not
reflect trends in opossum population abundance.
CONCLUSICES ANE RECCHEE1DATICNS
Scent-station transects have been used widely for
indexing the population trends of carnivorous mammals
without an independent verification of population abundance
(Wood 1S5S, Linhart and Knowlton 1975, Brady 1981, Sumner
and Hill 1980, Morrison et al. 1981, Humphrey and 2inn 1982,
and others). In this investigation, scent-station transects
provided a reliable index of the population abundance of
bobcats, raccoons, and gray foxes, tut prctably not of
opossums. Yet, despite the utility of the technique,
differences in operational methodology, such as the spacing
of transects and stations within transects, frequency of
operation, tracking surfaces, and type and presentation of
attractant, have minimized the comparability of
species-specific visitation rates among different geographic
regions. Therefore, standardization and verification of the
technique must be achieved to facilitate inter-area
comparisons.
Findings from this investigation, coupled with previously
published works, facilitated the formulation of some
guidelines for standardizing the scent-station technique,
for obtaining annual trends in the abundance of mammalian
carnivores. First, transects should be operated when
visitation is highest, as recommended by Roughton and Sweeny
(1982). Second, transects with stations spaced at 0.32 km
were demonstrated to be indicative cf trends in the
population abundance of bobcats, raccoons, and gray foxes;
therefore, this interval of station placement appears
feasible when indices for multiple species are to be derived
from the same transect network. Third, transects should be
distributed so as to proportionately sample all major
habitat types, particularly when indices for the raccoon are
required; replicate transects per habitat-type are required
if habitat use is to be measured. The area-wide
distribution of transects, i.e., the number of transects per
unit area, required to accurately reflect population trends
remains unknown. However, the characteristic home range
size and movement pattern of individual species are probably
the most important factors in determining appropriate
transect placement and spacing. Fourth, transects operated
for 1 night only will provide reliable indices for abundant
mammalian species (Roughtcn and Sweeny 1982, unreported data
from this project); however, multiple-night sampling should
be considered for rare or uncommon species. finally,
although not specifically addressed in this project,
tracking surfaces and attractants should also be
standardized. Stations should be constructed with the test
available natural material to minimize the possibility of
the tracking surface becoming an attractant or repellent.
The attractant and the tethcd of presentation should be
standardized as suggested by Roughtcn and Sweeny (1982).
This study provided 2 specific recommendations for
operating scent-station transects in Florida, if indices for
all carnivorous furtearers are to be developed from a
transect network that is operated only 1 night per year.
First, transects should be operated in October or November.
Second, a large proportion cf the transects should be
distributed in wetland habitats. If manpower and time
constraints permit transects to be operated more than once
per year, bobcats and gray foxes should be indexed in
November and raccoons in September. If transects are to be
targeted specifically for bobcats, the optimal station
spacing should be investigated further. The
characteristically large home ranges cf bobcats during
periods of low population abundance (Erogulske 1982)
indicates that more bobcat home ranges could be encountered
by increasing the transect length.
LIfERATURE CITED
Brady, J. E. 1981. Preliminary results of bobcat
scent-stations in Florida. Pages 101-103 is Bobcat
research conference proceedings: current research on
biology and management of Lynx rufus. Natl. ildl.
Fed. Sci. and Tech. Ser. 6.
Conner, M. C. 1982. Determination of bobcat (JLnx rufus) and
racccon (Procyon Iotor) population abundance by
radioisotope tagging. M.S. Thesis. Univ. Florida,
Gainesville. 55pp.
Davison. R. P. 1981. The effects of exploitation on some
parameters of coyote populations. Ph.D. Eissertation.
Utah State Univ.. Logan, 153pp.
Hon, T. 1981. Relative abundance of bobcats in Georgia:
survey techniques and preliminary results. Pages
104-106 in Bobcat research conference proceedings:
current research on biology and management of Lynx
rufus. Natl. Will. Fed. Sci. and Tech. Ser. 6.
Humphrey, S. E., and T. L. Zinn. 1982. Seasonal habitat use
by river otters and everglades mink in Florida. J.
Nildl. Manage. 46:375-381.
Johnson, N. F. 1981. Efforts to understand Kansas' bobcat
populations. Pages 37-39 in Ectcat research conference
proceedings: current research on biology and management
of Lynx rufus. Natl. Vildl. Fed. Sci. and Tech. Ser.
6.
Johnson, K. G., W. G. Minser, III, and M. E. feltoa. 1981. A
survey of procedures used for indexing population
trends of furbearers in the southeastern United States.
Dept. of For., Wildl., and Fish., Univ. Tennessee,
Kacxville. 5pp. mimeo.
Knowlton, F. F., and W. M. Tzilkowski. 1981. Trends in
bobcat visitations to scent-station survey lines in
western United States, 1972-1978. Pages 8-12 in Bobcat
research conference proceedings: current research on
biclcgy and management of Lynx rufus. Natl. Wildl.
Fed. Sci. and Tech. Set. 6.
Laessle, A. M. 1942. The plant communities of the Welaka
area. Univ. Florida Biol. Sci. Ser. 4:1-143.
Linhart, S. B., and F. F. Knowlton. 1S75. Determining
relative abundance of coyotes by scent station lines.
Wildl. Soc. Bull. 3:119-124.
Morrison, D. W., R. M. Edmunds, G. linsccmbe, and J. W.
Goertz. 1981. Evaluation of specific scent station
variables in northcentral Louisiana. Proc. Southeast.
Assoc. Fish and Wildl. Agencies. In press.
National Cceanic and Atmospheric Administration. 1974.
Climates of the states. Vol. 1. Water Inf. Cent., Inc.,
Port Washington, N.Y. 486pp.
Pimlott, D. H., J. A. Shannon, and G. B. Kolenosky. 1969.
The ecology of the timber wolf in Algonquin Provincial
Park. Ontario Dept. Lands and For. 92pp.
Progulske, D. R., Jr. 1982. Spatial distributions of bobcats
and gray foxes in eastern Florida. M.S. Thesis. Univ.
Florida, Gainesville. 63pp.
Richards, S. H., and 8. L. Hine. 1953. Wisconsin fox
populations. Wisconsin Conserv. Dept., Tech. Wildly.
Bull. 6. 78pp.
Roughton, R. D., and M. W. Sweeny. 1982. Refinements in
scent-station methodology for assessing trends in
carnivore populations. J. Will. Manage. 46:217-229.
Schultz, D. 1979. Timber and soil type map of the Research
and Education Center, Welaka, Florida. Inst. of Food
and Agric. Sci., Univ. Florida, Gainesville. 122pp
minec.
80
Sumner, P. W., and E. Hill. 1980. Scent-stations as
indices of abundance in some furtearers of Alabama.
Prcc. Southeast. Assoc. Fish. and Wildl. Agencies.
34:572-583.
Veno, P. A. 1976. Successional relationships of five Florida
plant communities. Ecol. 57:498-508.
Wood, J. E. 1959. Relative estimates cf fox population
levels. J. Wildl. Manage. 23:53-63.
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