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255
SURVIVAL AND SOURCES OF MORTALITY IN OCELOTS
AARON M. HAINES,1Feline Research Program, Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville,
700 University Boulevard, MSC 218, Kingsville, TX 78363-8202, USA
MICHAEL E. TEWES, Feline Research Program, Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville,
700 University Boulevard, MSC 218, Kingsville, TX 78363-8202, USA
LINDA L. LAACK, Laguna Atascosa National Wildlife Refuge, 22817 Ocelot Road, Los Fresnos, TX 78566, USA
Abstract: Survival and cause-specific mortality estimates are needed to develop effective conservation strategies for the
endangered ocelot (Leopardus pardalis) in the United States. We radiomonitored 80 ocelots (36 F, 44 M) from 1983
to 2002 and analyzed survival and cause-specific mortality rates. Pooled estimates of annual survival rates differed
between resident (S
ˆ=0.87) and transient (S
ˆ=0.57) ocelots (P=0.02); therefore, survival and cause-specific mortality
analyses were partitioned for resident and transient ocelots. Sex-specific annual survival was similar between resident
ocelots (M = 0.92, F = 0.83,P=0.16) and transient ocelots (M = 0.53, F = 0.63,P=0.75). Most mortalities were from
human (e.g., ocelot–vehicle collisions; M=45%) and natural (e.g., animal attack, disease; M=35%) sources. Transient
ocelots had higher natural mortality rates (disease, intraspecific mortality; M=0.26) than resident ocelots (M=
0.04,P=0.03). Other sources of mortality did not differ (P≥0.10) between resident or transient ocelots or male and
female resident or transient ocelots (P≥0.08). Human population expansion within the Lower Rio Grande Valley of
southern Texas, USA, will increase transportation-related problems and decrease the quantity of ocelot habitat, leading
to increased ocelot–vehicle collisions and possibly cause more transient behavior, thus significantly lowering ocelot sur-
vival. Research and development of ocelot road underpasses should be conducted to mitigate ocelot–vehicle collisions.
JOURNAL OF WILDLIFE MANAGEMENT 69(1):255–263; 2005
Key words: endangered species, Leopardus pardalis, mortality, ocelot, resident, survival, Texas, transient, vehicle collisions.
The ocelot population within the United States
once ranged from Arkansas to Arizona and is now
limited to 80–120 individuals in southern Texas
(Hall 1981, Tewes and Everett 1986). During 1989,
the ocelot was listed in Appendix I by the Conven-
tion on International Trade in Endangered Species
(CITES; Sunquist and Sunquist 2002), which pro-
hibits international commerce of skins (i.e., pelts)
and live animals. In addition, the ocelot is listed
as federally endangered within the United States
by the U.S. Fish and Wildlife Service (1982). Ocelot
persistence in a declining population can be
assisted by understanding population processes,
particularly factors affecting their survival.
Estimates of survival and cause-specific mortali-
ty rates are needed to assess population viability
and to develop conservation strategies (White
1983). Seasonal, age, and sex-specific survival
rates represent important information for con-
servation biologists to plan recovery strategies.
This information will allow biologists to identify
major sources of ocelot mortality and allow re-
searchers to model ocelot populations under dif-
ferent management scenarios to predict popula-
tion response. However, these estimates are
difficult to obtain for secretive, long-lived mam-
mals that occur at low densities, such as the
ocelot (Lindzey et al. 1988).
Estimates of small cat survival and cause-specific
mortality rates have been primarily limited to bob-
cat (Lynx rufus) studies in temperate regions of
the United States (Fuller et al. 1985,1995; Knick
1990; Chamberlain et al. 1999; Kamler and Gip-
son 2000; Nielsen and Woolf 2002). Bobcats are
similar to ocelots in size and co-occur with ocelots
in southern Texas (Tewes 1986). However, ocelots
are more specialized, requiring areas of dense cover
and high rodent density (Tewes 1986, Emmons
1988). The few ecological studies on ocelots have
not reported survival or mortality rates (Emmons
1987, Ludlow and Sunquist 1987, Konecny 1989,
Crawshaw 1995). Results of our study represent the
first assessment of these population parameters for
ocelots. Our objectives were to (1) estimate season-
al and annual survival for male and female resident
and transient ocelots, (2) estimate annual survival
for resident and transient ocelots during drought
conditions, (3) estimate seasonal and annual cause-
specific mortality rates for male and female resident
and transient ocelots, and (4) evaluate differences
in seasonal and annual survival rates and differ-
ences in cause-specific mortality rates between
male and female resident and transient ocelots.
We hypothesized that (1) survival of transient
ocelots will be 50% lower than resident ocelots
because transients will be more susceptible to
mortality (e.g., vehicle collision, intraspecific
mortality) in unfamiliar environments, (2) ocelot
survival will be similar between male and female
1E-mail: ksamh03@tamuk.edu
J. Wildl. Manage. 69(1):2005256 OCELOT SURVIVAL AND MORTALITY • Haines et al.
resident and transient ocelots, as is the case with
unexploited bobcats (Nielson and Woolf 2002),
(3) ocelot survival will be 25% lower during
drought conditions because prey resources will be
limited, and (4) unnatural sources of mortality
(e.g., ocelot–vehicle collisions) will represent
80% of total mortalities for both resident and
transient ocelots, as found with unexploited bob-
cats (Nielsen and Woolf 2002).
STUDY AREA
We monitored ocelots in Laguna Atascosa Na-
tional Wildlife Refuge located in Cameron Coun-
ty, within the Lower Rio Grande Valley (LRGV) of
southern Texas, USA (Fig. 1). Laguna Atascosa
National Wildlife Refuge is an 18,200-ha refuge
that provides wintering and feeding areas for
migratory waterfowl and habitat for ocelots. The
LRGV is an alluvial plain dissected by numerous
arroyos and ephemeral streams that flow into the
Rio Grande River or the Gulf of Mexico (Everitt
and Drawe 1993). The LRGV had diverse fertile
soil types (Williams et al. 1977). The subtropical,
semi-arid climate is characterized by hot summers
and mild winters (Thornthwaite 1948, Lonard
and Judd 1985). Mean length of the frost-free
period was 330 days with winters frequently occur-
ring without freezing temperatures. Mean annual
temperature and rainfall were 23°C and 68 cm,
respectively; however, rainfall fluctuated widely
through the year (Nor-
wine and Bingham 1985,
Lonard et al. 1991).
This region supports
various plants, wildlife,
and habitats as part of
the Tamaulipan Biotic
Province (Blair 1950,
Richardson 1995). Pre-
dominant woody species
in the LRGV include
spiny hackberry (Celtis
pallida), crucita (Eupatori-
um odoratum), Berlandier
fiddlewood (Citharexylum
berlandieri), honey mes-
quite (Prosopis glandulosa),
desert olive (Forestiera
angustifolia), snake-eyes
(Phaulothamnus spine-
scens), colima (Zanthoxy-
lum fagara), and brasil
(Condalia hookeri; Lonard
and Judd 1993). Howev-
er, >95% of the native rangeland in the LRGV has
been converted to agricultural and urban land
uses (Jahrsdoerfer and Leslie 1988).
METHODS
Trapping and Radiotelemetry
During 15 September 1982 to 11 November
2001, we captured 80 ocelots (36 F, 44 M) with sin-
gle-door, 108 × 55 × 40 cm wire box traps (Toma-
hawk Trap Co., Tomahawk, Wisconsin, USA). We
attached a separate compartment containing a
domestic live chicken to the trap as bait. We
placed traps in shaded areas and checked each
morning to reduce the risk of hyperthermia.
We immobilized ocelots with a 9:1ratio of keta-
mine hydrochloride and acepromazine maleate
(Beltran and Tewes 1995). We injected this mix-
ture with a pole syringe at a dosage of 20 mg/kg
body weight. We sexed, weighed, and classified
ocelots as adults or subadults based on matura-
tion of morphological development, dental wear
(sharp dentition for juveniles), canine length
(>15 mm for adults), and weight (female adults
>6.5kg, male adults >8.5kg). We fitted immobi-
lized adult and subadult ocelots with collar-mount-
ed radiotransmitters containing a mortality sensor
and a frequency of 148−149 MHz (Telonics, Mesa,
Arizona, USA). We used ground stations and aer-
ial radiotelemetry to locate ocelots 2–3times each
Fig. 1. Map of the Laguna Atascosa National Wildlife Refuge located in the Lower Rio Grande
Valley, eastern Cameron County, Texas, USA.
J. Wildl. Manage. 69(1):2005 257
OCELOT SURVIVAL AND MORTALITY • Haines et al.
week anytime between 1hr before sunrise until 1
hr after sunset. We monitored radio signals with a
directional H-antenna connected to a model LB12
receiver (Telonics Inc.). We located and recovered
dead ocelots to determine cause of mortality. We
conducted tracking from a small aircraft if a collared
ocelot could not be found during ground searches.
We classified mortality into 4categories based on
field observations and necropsy information:
vehicle-caused, natural cause (i.e., mammal attack,
disease), unknown, or other (other anthropogenic
induced mortality; Tewes 1986, Laack 1991).
Survival and Cause-specific Mortality
We estimated annual and seasonal survival rates
and cause-specific mortality rates of resident and
transient ocelots using number of transmitter-
days and total number of deaths within a defined
time interval (Trent and Rongstad 1974, Heisey
and Fuller 1985a). This was done using program
MICROMORT (Heisey and Fuller 1985b), which
is based on the Mayfield methodology (Mayfield
1961,1975). To meet the assumptions of the May-
field method, we assumed that constant survival
occurred during the hot (16 Apr–15 Oct) and
cool (16 Oct–15 Apr) seasons in the study area.
Study assumptions included that newly collared
ocelots had the same survival rate as previously
collared ocelots, sampled ocelots were random
and independent, working collars were always
located, censoring was random, and trapping,
handling, and radiocollaring did not impact
ocelot survival (Winterstein et al. 2001). We used
ocelots with transmitter failure in the data analy-
sis for survival probabilities until signal loss
occurred (Burger et al. 1995). We censored these
cats from the survival analysis, but they were not
considered mortalities (Pollock et al. 1989).
We pooled data across years because low annu-
al sample sizes would have resulted in a low sta-
tistical power for the tests (Fuller et al. 1985, Cun-
ningham et al. 2001, and Nielsen and Woolf
2002). Nielsen and Woolf (2002) stated that test-
ing for differences in annual survival rates over
years would have been biased due to differing
number of radio days occurring for each year.
Hence, Nielsen and Woolf (2002) believed that
testing for differences in survival between years is
unfounded and biologically meaningless (Yoccoz
1991, Cherry 1998). However, we did not pool
years during 1989–1991 or 2000–2002 because
during these years, the 12-month Palmer Modi-
fied Drought Severity Index (PMDI)—which
assesses the severity of dry or wet conditions—was
consistently lower from January 1989 to April
1991 and January 2000 to December 2002 than
from January 1983 to December 1988 and May
1991 to December 1999 (Fig. 2).
Fig. 2.The 12-month Modified Palmer Drought Severity Index within the Lower Rio Grande Valley of Texas, USA, Jan 1983–Dec 2002.
J. Wildl. Manage. 69(1):2005258 OCELOT SURVIVAL AND MORTALITY • Haines et al.
Blankenship (2000) found that on the Welder
Wildlife Refuge (WWR) in San Patricio County,
Texas, bobcat survival, fecundity, and prey densi-
ty dropped dramatically during drought condi-
tions in 1996. During 1996, the mean 12-month
PMDI was –2.52 within the WWR area, which
indicated moderate drought conditions. From
January 1989 to May 1991 and January 2000 to
December 2002, the mean 12-month PMDI was
–2.42 and –2.48 within LRGV of Texas (which also
indicated moderate drought conditions), where-
as the mean 12-month PMDI from January 1983
to December 1988 and May 1991 to December
1999 was 0.55 and 0.11 (which indicated normal
moisture conditions; National Climatic Data Cen-
ter; http:
//
www.ncdc.noaa.gov). Consequently,
we analyzed survival of ocelots separately from
January 1989 to May 1991 and January 2000−2002
to minimize differences in survival between years
so they can be pooled. We analyzed cause-specif-
ic mortality from January 1982 to December 2002.
We used chi-square tests in the program CON-
TRAST to test for differences in annual survival
and annual cause-specific mortality between resi-
dent and transient ocelots, and we pooled annu-
al survival and cause-specific mortality rates
between sexes and seasons for resident and tran-
sient ocelots (Hines and Sauer 1989, Sauer and
Williams 1989). We tested for differences in annu-
al and seasonal survival rates and annual and sea-
sonal mortality rates between male and female
resident ocelots, and between male and female
transient ocelots. We also tested for differences in
annual survival rates during drought and normal
conditions for resident and transient ocelots.
Experiment wise error rate was maintained dur-
ing associated multiple comparisons by adjusting
αwith a Bonferroni correction factor (α/no. of
comparisons; Neter and Wasserman 1974). Statis-
tical significance was inferred at P≤0.05.
We defined resident ocelots as an individual
that used a single restricted area (home range)
for 3months or more, and we defined transient
ocelots as an individual that moved from the
natal or breeding range and traveled nomadi-
cally until a stable range was established. We
applied a resident status to transient ocelots fol-
lowing establishment of a stable breeding range.
We correctly classified most transients as sub-
adults with ocelots usually leaving their natal
range at 2–3years of age (Sunquist and Sunquist
2002). Resident ocelots included juvenile cats still
residing on their natal range and adult cats with
a defined breeding range.
RESULTS
From 1January 1983 to 31 December 2002, we
used 72 resident (33 F, 39 M) and 20 transient (6
F, 14 M) ocelots for 50,901 radio days (x
–
days/ocelot = 749, range 11–1,669 days) for sur-
vival and cause-specific mortality analyses. Indi-
vidual ocelots sometimes shifted between resi-
dent and transient status. We monitored resident
ocelots for 46,550 radio days (x
–=647
days/ocelot, range 45−1,669 days) and transient
ocelots were monitored for 4,641 radio days (x
–=
218 days/ocelot, range 11−645 days). We moni-
tored resident female ocelots for more radio days
(25,549) than male residents (21,001 radio days)
and male transient ocelots for more radio days
(3,511) than female transients (1,130 radio days).
Twenty-nine mortalities occurred during the
study with 21 residents (14 F, 7M) and 8tran-
sients (2F, 5M). Mortalities within resident
ocelots included 7(33%) vehicle-caused and 6
natural mortalities (29%). Natural mortalities
included 2diseased (chronic ear infection, heart-
worm {Dirofilaria immitis} infestation), 3aggressive
animal encounters (e.g., rattlesnake [Crotalus
atrox] bite, attack from another cat, attack from
another animal leading to septic peritonitis and
pleuritis), and 1predation. Five (24%) resident
ocelot mortalities were unknown, and we classi-
fied 3(14%) resident ocelot mortalities as other
(killed by dogs [Canis domesticus], capture hyper-
thermia, and poisoned by organophosphate
aldicarb [illegal predator control agent]). Mor-
talities within transient ocelots included 4(50%)
natural mortalities (1mange, 1lung abscess from
plant material, 2intraspecific mortality), 3
(37.5%) vehicle-caused, and 1(12.5%) unknown.
Overall, mortalities for ocelots did not differ dra-
matically between the cool (n=14,48%) and hot
(n=15,52%) season. Vehicle-caused (35%) and
natural (35%) mortalities were the highest
sources of mortalities for ocelots in south Texas
followed by unknown (20%), and other (10%)
mortalities. Unnatural mortalities constituted
45% of total mortalities, which was lower than the
80% we had hypothesized.
Survival
From January 1983 to December 1999, during
normal conditions, resident ocelots had a 30%
higher annual survival rate than transient ocelots
(Table 1). This supported our hypothesis that res-
ident ocelot survival would be higher than tran-
sient ocelot survival, albeit not 50% higher. Annu-
al survival rates did not differ (χ2
1=1.98,P=0.16)
J. Wildl. Manage. 69(1):2005 259
OCELOT SURVIVAL AND MORTALITY • Haines et al.
between male and female resident ocelots or
between male and female transient ocelots (χ2
1=
0.10,P=0.75; Table 1). This supported our hypoth-
esis that survival between sexes would be similar.
Because annual survival differed (χ2
1=5.22,P=
0.02) between resident and transient ocelots, we
analyzed survival and cause-specific mortality
rates separately between resident and transient
ocelots. For resident ocelots, survival did not dif-
fer between the cool and hot season (Table 1).
For transient ocelots, survival also did not differ
(χ2
1=0.54,P=0.46) between the cool and hot sea-
son (Table 1). Survival did not differ (χ2
1=1.25,P
=0.26) between male and female resident ocelots
or between male and female transient ocelots
during the cool season (χ2
1=3.00,P=0.08; Table
1). During the hot season, male survival was
higher (χ2
1=5.01,P=0.02) than female survival
for resident ocelots (Table 1), while survival
between male and female transient ocelots did
not differ (χ2
1=0.07,P=0.79; Table 1).
During drought conditions annual survival of
resident ocelots (S
ˆ=0.77, SE 0.07) was higher (χ2
1
=6.08,P=0.01) than for transient ocelots (S
ˆ=0.13,
SE 0.25). We monitored 27 (16 F, 11 M) resident
ocelots during the drought periods (Jan 1989–
Apr 1991 and Jan 2000−Dec 2002) for 11,725
radio days (x
–days/ocelot = 434, range 20–1,095
radio days). Annual survival of resident ocelots
during drought conditions (S
ˆ=0.77, SE 0.07) did
not differ significantly (χ2
1=1.89,P=0.17) from
resident ocelot annual survival during normal
conditions (Jan 1983–Dec 1988 and May 1991–
Dec 1999;S
ˆ=0.87, SE 0.05). Resident ocelot sur-
vival during drought
conditions decreased by
10%, this supported our
hypothesis that ocelot
survival would decrease
during drought periods.
However, this decrease
was not significantly dif-
ferent and was not as
severe as the 25% decline
we hypothesized. We
monitored 4(2F, 2M)
transient ocelots during
the drought periods for
553 radio days (x
–days/
ocelot = 136.5, range
11–175 radio days), with
1individual suffering
from an intraspecific
attack, another from an
unknown mortality, and 2with lost radio signals.
Annual survival of transient ocelots during
drought conditions (S
ˆ=0.13, SE 0.25) did not dif-
fer significantly (χ2
1=2.44,P=0.12) from tran-
sient ocelots (S
ˆ=0.57, SE 0.13) during normal
conditions. However, we attribute this nonsignifi-
cance to the low number of radio days of tran-
sients during the drought period.
Cause-specific Mortality
Cause-specific mortality did not differ for resi-
dent (χ2
1=1.61,P=0.20), or transient ocelots (χ2
1
≤1.06,P≥0.30) during the cool and hot season
(Table 2). In addition, cause-specific mortality of
male and female resident ocelots did not differ
during the cool season (χ2
1≤2.25,P≥0.13) or the
hot season (χ2
1≤3.11,P≥0.08). Similarly, cause-
specific mortality of male and female transients
did not differ during the cool season (χ2
1≤ 1.44,
P≥0.23) or the hot season (χ2
1≤2.89,P≥0.09).
Cause-specific mortality differed between resi-
dent and transient ocelots (χ2
1=4.70,P=0.03),
with transient ocelots having higher natural mor-
tality (M=0.26, SE 0.10) than resident ocelots (M
=0.04, SE 0.02). Other forms of mortality did not
significantly differ between resident and tran-
sient ocelots (χ2
1≤2.78,P≥0.10; Table 2).
If we include mortality data from collared and
uncollared ocelots from 1983–2002, the summary
of mortality rates include 26 (45%) road mortali-
ties; 4(7%) other human-caused mortalities; 6
(10%) disease, parasitism, infection; 8(14%) pre-
dation, aggression; and 14 (24%) unknown mor-
talities. However, direct human-caused mortality
Table 1. Seasonal and annual survival rates (
S
ˆ) of male and female resident and transient
ocelots in Cameron County, Texas, USA, January 1983–31 December 1988 and 2 April
1991–31 December 1999 during normal moisture conditions.
Residents Transients
Mortalities Radio days
S
ˆSE Mortalities Radio days
S
ˆSE
Male
Coola4 8,368 0.92 0.04 2 1,318 0.74 0.15
Hotb0 8,388 1.00 0.00 3 1,696 0.71 0.13
Annual 4 16,756 0.92 0.04 5 3,014 0.53 0.15
Female
Cool 4 8,595 0.92 0.04 0 605 1.00 0.00
Hot 5 9,474 0.91 0.04 1 469 0.63 0.27
Annual 9 18,069 0.83 0.05 1 1,074 0.63 0.27
Pooled
Cool 8 16,963 0.92 0.03 2 1,923 0.82 0.11
Pooled
Hot 5 17,862 0.95 0.04 4 2,165 0.70 0.12
Annual 13 34,825 0.87 0.02 6 4,088 0.57 0.13
a16 Oct–15 Apr.
b16 Apr–15 Oct.
J. Wildl. Manage. 69(1):2005260 OCELOT SURVIVAL AND MORTALITY • Haines et al.
may be overrepresented as they were more likely
to be found.
DISCUSSION
Our study provided the first survival and cause-
specific mortality rates for ocelots. Resident oce-
lots exhibited a 30% higher survival than tran-
sient ocelots. Most transients were subadult
individuals probably attempting to identify a breed-
ing range; whereas, 3transients were adult indi-
viduals probably trying to reestablish a breeding
range elsewhere. Resident adult ocelots killed 2
transient ocelots. Intraspecific mortality within
felids has been previously documented (Litvaitus
et al. 1982, Zezulak and Minta 1987, Logan and
Sweanor 2001). Intrasexual defense of a breeding
range from intruding conspecifics is suspected
for male and female ocelots (Tewes 1986, Laack
1991). Both mortalities coincided with the arrival
of a same-sex intruder into an established breed-
ing range of a resident ocelot, with the transient
intruders exhibiting puncture wounds, and claw
marks as lacerations and scratches. Soon after 1
of the transient mortalities was found, the resi-
dent ocelot of the area was captured and had
claw scratches on its body. The canine spacing of
the resident cat matched the cranial fracture
wounds of the dead transient found on its range.
Another source of natural mortality for a tran-
sient ocelot was notoedric mange, which had
been previously reported in ocelots from south-
ern Texas (Pence et al. 1995).
In 3different studies that monitored the dis-
persal of 11 ocelots, 5ocelots survived until study
termination, humans directly killed (shot) 5indi-
viduals, and a resident
ocelot killed 1individual
(Ludlow and Sunquist
1987, Emmons 1988,
Crawshaw 1995). Tran-
sient ocelots may be more
susceptible to mortality
by traveling over large
unfamiliar areas, thus in-
creasing the possibility
of road kills, encounter-
ing other anthropogenic
mortalities, and increased
likelihood of intraspecific
mortality and other ani-
mal attacks. Sunquist
and Sunquist (2002)
stated that cat move-
ment over a large area
increases encounters with highways and humans,
the 2primary sources of mortality for wild cats.
Kamler and Gipson (2000) found that the sur-
vival rate of resident bobcats was twice as high as
transient bobcats. They attributed this difference
to resident bobcats occupying a military base that
served as a refuge, and transient bobcats suscep-
tible to hunting, trapping, and being vulnerable
within unfamiliar areas.
Annual survival was similar between male and
female resident and transient ocelots. Knick (1990)
and Nielson and Woolf (2002) found that annual
survival of male and female radiomonitored
adult bobcats in unexploited populations were
similar. We found a difference in sex-specific sea-
sonal survival between male and female resident
ocelots during the hot season with male resident
ocelots having a higher annual survival rate than
female residents. We have no explanation for this
difference in survival. Chamberlain et al. (1999)
found that female bobcat survival was lower dur-
ing the parturition–young-rearing period (1
Jun–30 Sep) in central Mississippi. However,
ocelots lacked a distinct breeding season and may
breed when environmental conditions are favor-
able (Tewes 1986, Laack 1991).
Favorable environmental conditions in south-
ern Texas may be dictated by precipitation, which
fluctuates widely between seasons and among
years; thus, we partitioned ocelot survival by nor-
mal and drought periods. During drought condi-
tions resident ocelots still had a higher annual
survival rate than transient ocelots. Survival of
resident ocelots during drought periods (S
ˆ=
0.77) did not differ significantly from resident
Table 2. Pooled seasonal and annual cause-specific mortality rates (
M
) of male and female
resident and transient ocelots in Cameron County, Texas, USA, 1 January 1983–31 Decem-
ber 2002.
Residents Transients
Mortality cause Mor talities
M
SE Mortalities
M
SE
CoolaVehicle 5 0.040 0.017 1 0.080 0.078
Natural 3 0.020 0.014 2 0.160 0.100
Unknown 2 0.015 0.010 0 0.000 0.000
Other 1 0.010 0.001 0 0.000 0.000
HotbVehicle 2 0.015 0.010 2 0.130 0.080
Natural 3 0.020 0.014 2 0.130 0.080
Unknown 3 0.020 0.014 1 0.065 0.063
Other 2 0.015 0.010 0 0.000 0.000
Annual Vehicle 7 0.050 0.020 3 0.180 0.095
Natural 6 0.040 0.017 4 0.260 0.100
Unknown 5 0.036 0.017 1 0.050 0.045
Other 3 0.020 0.012 0 0.000 0.000
a16 Oct–15 Apr.
b16 Apr–15 Oct.
J. Wildl. Manage. 69(1):2005 261
OCELOT SURVIVAL AND MORTALITY • Haines et al.
ocelots during normal conditions (S
ˆ=0.87). In
addition, there was no significant difference
between the survival of transient ocelots during
drought (S
ˆ=0.13) and normal (S
ˆ=0.57) condi-
tions. However, the number of individual tran-
sient ocelots radiomonitored during drought con-
ditions was only 4. This reduction in the number
of radiomonitored transient ocelots during
drought conditions may be due to (1) young
ocelots staying within natal ranges during drought
periods, (2) adult females producing few young
during drought periods, or (3) the population of
transient ocelots crashing during drought peri-
ods. More research is needed to test why the
number of individual transient ocelots decreased
during drought conditions. Blankenship (2000)
found that during a drought year when primary
prey of bobcats was reduced, bobcats had lower
survival, no fecundity, and increased transient
behavior. More research is needed to monitor
the effects of drought conditions on ocelot fecun-
dity and behavior.
Cumulative survival rates of resident ocelots (S
ˆ
=0.87) was similar to survival rates of unexploit-
ed bobcats in Illinois (S
ˆ=0.82; Nielsen and
Woolf 2002) but higher than unexploited bobcats
in Idaho (S
ˆ=0.67; Knick 1990). However, Knick
(1990) and Nielsen and Woolf (2002) did not dif-
ferentiate between transient and resident bob-
cats. Knick (1990) found 50% bobcat mortalities
in an unexploited population in Idaho were
human-related. Nielsen and Woolf (2002) found
19 mortalities with 10 bobcats (52%) hit by auto-
mobiles and human activities causing 79% of the
cumulative mortality. In our study both resident
and transient ocelot mortalities were caused by
both anthropogenic (e.g., vehicle collisions) and
natural mortality (predation) factors, with tran-
sient ocelots having a higher rate of natural mor-
talities. We documented 29 total mortalities with
human activity causing 45% of the cumulative
mortality. However, natural mortality may be indi-
rectly related to anthropogenic habitat fragmen-
tation. Reduced habitat availability may cause
ocelot populations to be more crowded, thus in-
creasing intraspecific conflict, competition, and
disease transmission.
When analyzing the assumptions of the May-
field method for calculating survival in this study
there was no evidence to support that any of the
assumptions had been violated, with maybe 1
exception. One radiocollared ocelot was recap-
tured and suffered from capture hyperthermia.
However, this was the only documented case in
which an ocelot died from trapping and handling
techniques during this 20-year study. Further, no
ocelots were found dead directly after being col-
lared. The shortest time interval from when an
ocelot was originally collared until it experienced
mortality was 95 days.
Our study found fewer female transients than
male transients. There are usually fewer female
transients than male transients in populations of
solitary cats because females usually settle adja-
cent to or within their natal range to breed (Sun-
quist and Sunquist 2002). This same pattern of
behavior has been documented for tiger (Pan-
thera tigris), leopard (Panthera pardus), Iberian
lynx (Lynx pardinus), and puma (Puma concolor;
Smith et al. 1987, Bailey 1993, Lindzey et al. 1994,
Ferreras et al. 1997).
MANAGEMENT IMPLICATIONS
Vehicle-caused mortality seems to be the pri-
mary anthropogenic factor causing ocelot deaths
in the LRGV of southern Texas. Applications of
remedial tactics within transportation corridors
to promote safer felid movements have been pro-
posed to minimize ocelot mortality, including cat
underpasses (e.g., culverts), which have been
constructed for ocelots in southern Texas (Tewes
and Blanton 1998, Tewes and Hughes 2001). Pro-
posed culverts should be placed in relation to
habitat features and travel corridors, with barrier
fences guiding cats to the culverts and crossing
structures allowing for water drainage (Tewes
and Hughes 2001, Cain et al. 2003). In addition,
Beier (1995) recommended that artificial light-
ing and unrestrained pets should be excluded
from culverts. However, culvert utility and effec-
tiveness in reducing vehicular-caused ocelot mor-
tality still needs to be assessed, and ocelot travel
corridors should be assessed prior to construc-
tion of expensive culverts, as well as other devel-
opments that are designed for ocelot passage at
specific locations (Tewes and Hughes 2001). This
can be done by placing remote cameras within
culverts or at proposed culvert locations to mon-
itor ocelot activity and using telemetry to moni-
tor ocelot movements around major roadways.
ACKNOWLEDGMENTS
Our project was funded by the Rob and Bessie
Welder Wildlife Foundation, U.S. Fish and Wild-
life Service, Environmental Conservation Fellow-
ship from the National Wildlife Federation, and
the Boone and Crocket Club. We thank person-
nel from the Laguna Atascosa National Wildlife
J. Wildl. Manage. 69(1):2005262 OCELOT SURVIVAL AND MORTALITY • Haines et al.
Refuge, H. Cullen, C. Corbett, M. Corbett, and F.
Yturria for granting permission to use their land.
We also thank L. Drawe, D. Everett, M. Fernan-
dez, E. Haines, S. Jojola, D. Miller, B. Radabaugh,
J. Rappole, and B. Tewes for their help in the
field, data collection, and support of the project.
Other personnel with the U.S. Fish and Wildlife
Service instrumental in the success of this study
were G. Burke, C. Carley, T. Jasikoff, S. Rice, R.
Rauch, and S. Thompson. We thank M. Hornocker
and the Wildlife Research Institute of the Univer-
sity of Idaho for their support facilities, and we
thank S. Henke for reviewing this manuscript. The
views expressed within this manuscript reflect that
of the authors and do not necessarily reflect the
views of the U.S. Fish and Wildlife Service. This is
Publication 04-109 of the Caesar Kleberg Wildlife
Research Institute and Contribution 610 of the
Rob and Bessie Welder Wildlife Foundation.
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