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Reproductive life history of ocelots Leopardus pardalis
in southern Texas
Linda L. LAACK, Michael E. TEWES,
Aaron M. HAINES and John H. RAPPOLE
Laack L. L., Tewes M. E., Haines A. M. and Rappole J. H. 2005. Reproductive life
history of ocelots Leopardus pardalis in southern Texas. Acta Theriologica 50:
505–514.
The ocelot Leopardus pardalis Linnaeus, 1758 is an endangered felid in the
United States currently restricted to southern Texas. The objectives of our study were
to obtain data on ocelot parturition dates, fecundity, sex ratios, den characteristics,
and first year survival, all of which are critical in development of population viability
models. Sixteen parturition events were recorded ranging from mid-April to late
December for 12 wild ocelots. Cumulatively, litters consisted of 1 or 2 kittens (
x
= 1.2
± 0.44 SD). Cumulative sex ratio was 1:2.5 (male:female); however, there was no
significant difference between the observed sex ratio and a 1:1 sex ratio. Ten den sites
were in close proximity (£ 10 m) to dense thornshrub. Adult female ocelots used 2 to 4
den sites for each litter with distance between consecutively occupied dens ranging
from 110 to 280 m (
x
= 158 m ± 93 SD). An estimated annual survival for ocelots 0 to 1
year of age was 0.68. Evidence suggests that ocelots in the wild may breed more
frequently than had been previously hypothesized.
Laguna Atascosa Na tional Wild life Ref uge, 22817 Oce lot Rd., Los Fresnos, TX 78566,
USA, e-mail: Linda_Laack@fws.gov (LLL); Fe line Re search Pro gram, Caesar Kleberg
Wild life Re search In sti tute, Texas A&M Uni ver sity-Kingsville, 700 Uni ver sity Bou le -
vard, MSC 218. Kingsville, TX 78363-8202, USA (MET, AMH); Smit hsoni an’s Na tion al
Zoo log ical Park, Con ser vati on & Re sea rch Cen ter 1500 Re mou nt Road, Front Royal,
VA 22630, USA (JHR)
Key words: Leopardus pardalis, den sites, fecundity, ocelot, reproduction, southern
Texas
Introduction
The ocelot Leopardus pardalis (Linnaeus 1758) is listed as an endangered
species in the United States (U.S.) (U.S. Fish and Wildlife Service 1982). Its
population, now restricted to southern Texas, is estimated at 80 to 120 individuals
(Tewes and Everett 1986). Information on reproductive characteristics of North
American ocelots (eg fecundity, kitten survival) is lacking and needed to develop
models of population viability. However, the low density of ocelots, as well as their
nocturnal habits and preference for dense cover (Tewes 1986, Laack 1991)
make reproductive information difficult to obtain. Most information on ocelot
[505]
Acta Theriologica 50 (4): 505–514, 2005.
PL ISSN 0001–7051
reproduction is from captive individuals (Cisin 1967, Eaton 1977, Fagen and
Wiley 1978, Mellen 1989). Captive ocelots have small litters, long gestation
periods, and slow growth rates compared to other felids of similar size. Repro-
ductive information on wild ocelots is based on circumstantial data provided by
Emmons (1988). A review of ocelot reproductive life history is provided by
Sunquist and Sunquist (2002).
The results of our study provide further information about wild ocelot re-
productive life history in the U.S. We report on parturition dates, breeding dates,
fecundity, sex ratios, den characteristics, and first year-survival of ocelots in
southern Texas. These results were part of on-going broader ecological study of
the ocelot in southern Texas that began in the early 1980s (Tewes 1986).
Study area
Laguna Atascosa National Wildlife Refuge (LANWR) in Cameron County is located within the
Lower Rio Grande Valley (LRGV) of southern Texas, U.S. (26°24’–26°09’N, 97°23’–97°17’W). The
subtropical, semiarid climate is characterized by hot summers and mild winters (Thornthwaite 1948,
Lonard and Judd 1985). Mean length of the frost-free period is 330 days with winters frequently
occurring without freezing temperatures. Mean annual temperature and rainfall were 23°C and 68
cm, respectively, although rainfall fluctuates widely during and among years (Norwine and Bingham
1985, Lonard et al. 1991).
The LRGV supports a variety of plants, wildlife, and habitats as part of the Tamaulipan Biotic
Province (Blair 1950, Richardson 1995). Predominant woody plant species that constitute the majority
of thornshrub forest in the LRGV include spiny hackberry Celtis pallida, Texas ebony Pithecellobium
flexicaule, crucita Eupatorium odoratum, Berlandier fiddlewood Citharexylum berlandieri, honey
mesquite Prosopis glandulosa, desert olive Forestiera angustifolia, snake-eyes Phaulothamnus
spinescens, colima Zanthoxylum fagara, and brasil Condalia hookeri (Lonard and Judd 1993).
However, > 95% of the native rangeland in the LRGV has been converted for agricultural and urban
land uses (Jahrsdoerfer and Leslie 1988).
Material and methods
Trapping and monitoring
We captured ocelots with single-door, 108 × 55 × 40 cm wire box traps (Tomahawk Trap Co.,
Tomahawk, WI) from September 1982 to July 1997. 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.
Ocelots were immobilized with a 9:1 ratio of ketamine hydrochloride and acepromazine maleate.
We injected this mixture 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 maturation of morphological development,
dental wear (sharp dentition for juveniles), canine length (> 15 mm for adults), and weight (female
adults > 6.5 kg, male adults > 8.5 kg) (Tewes 1986, Laack 1991). Ocelots were fitted with a collar-
-mounted radio transmitter having a frequency of 148 to 149 MHz and an activity sensor (Telonics
Inc., Mesa Arizona). We located ocelots 2-3 times each week anytime between 1 hr before sunrise
until 1 hr after sunset. Radio signals were monitored with a directional H-antenna connected to a
model TR-2 receiver (Telonics Inc., Mesa, AZ), and we used ground stations and aerial radio
telemetry to locate ocelots. Trapping and handling of ocelots were performed in a humane manner
506 L. L. Laack et al.
with procedures and research methodology approved by the Texas A&M University-Kingsville
Institutional Animal Care and Use Committee protocol # 1989–5–19.
Identifying breeding females and den sites
Female ocelots handled during captures were suspected of having young if they were lactating or
had brown-stained fur around the teats (signifying post-lactation). In addition, parturition was
suspected if radio-collared adult female ocelots were located at the same site during the daytime for
1–2 weeks. We found this pattern characteristic of denning behavior. We subsequently searched for
suspected dens 2 to 5 weeks after the presumed parturition date. Dens were found by approaching a
radio-collared female until it moved, then searching the area around its last known location. Once
the den was found, kittens were then photographed, weighed in a bag with a scale, and measured in
length with measuring tape from tip of the nose pad to the base of the tail bone. Time spent by
researchers at the den was £ 30 min. An adult female ocelot was monitored until it returned to the
den site. Some dens were not found because of the difficulty of researchers quietly approaching
ocelots in dense vegetation and the concealment of the den. However, if a female displayed denning
behavior for ³ 6 weeks, parturition was presumed to have occurred. Female radio-collared ocelots
with known den sites were suspected of moving den sites when denning behavior was exhibited at a
different location from the initial den site. These new den site locations were estimated with
triangulation. However, we only took measurements at initial den sites to reduce potential stress to
ocelot females and kittens.
Parturition date was determined as the first day a female was found at the presumed site.
Breeding date was determined as 80 days prior to parturition date based on a gestation length of 79
to 82 days for captive ocelots (Cisin 1967, Eaton 1977, Fagen and Wiley 1978).
After den sites were abandoned by ocelots, we recorded general characteristics of the den sites.
These included den site distance to dense thornshrub cover, dimensions of den sites, and identification
of plant species within den chambers. Distance to dense thornshrub cover and dimensions of den
sites were measured with measuring tape.
Statistical analysis
We calculated differences between observed and expected sex ratios using a chi-square analysis.
Survival rates for ocelot kittens aged 0–3 months of age were calculated using number of observation-
-days and number of mortalities (Trent and Rongstad 1974, Heisey and Fuller 1985a) in MICROMORT
(Heisey and Fuller 1985b), a program based on the Mayfield methodology (Mayfield 1961, 1975). We
assumed no ocelots died before den sites were found due to no evidence of kitten mortality at the den
sites. To calculate first year survival for ocelots, we incorporated survival data from Haines et al.
(2005), and extrapolated it with our own data. Haines et al. (2005) defined a resident individual as an
ocelot ³ 6 months of age that inhabited a home range or natal range for ³ 3 months, and calculated
an annual survival rate of S
^
= 0.87 ± 0.02 SE for resident ocelots. Using the same data as Haines et
al. (2005) we calculated an annual survival rate of S
^
= 0.90 ± 0.04 SE for resident ocelots residing on
a natal range (juvenile and subadult ocelots). Both survival rates did not significantly differ (÷
2
1
=
0.45, p = 0.50) from each other when compared using chi-square tests in the program CONTRAST
(Hines and Sauer 1989, Sauer and Williams 1989). Thus, we combined resident ocelot survival rates
with our survival estimate for ocelots 0-3 months of age to calculate an estimate of ocelot first year
survival.
Results
We captured and monitored 15 resident adult females in their established
breeding ranges. Eleven produced young or exhibited denning during this time.
Sixteen parturition events were determined for 12 ocelots (Table 1). Failure to
Reproductive history of Leopardus pardalis 507
record young or denning behavior with the other 4 resident female ocelots may
have been a result of short monitoring periods. One radio-collared female (female
3) was road-killed 5 months following establishment of a breeding range, and was
carrying 2 fetuses. An uncollared female with 1 fetus (female 6) was also a
road-kill. In June 1989, the den site for female 4 was investigated with a kitten
only being heard around the den site. Thus, the kitten was not sexed (Table 1).
Ocelot litters were found from mid-April to late December, indicating a minimum
range of breeding activity from late January to early October (Table 1).
Two ocelots exhibited a 1-year interbirth period following the success of a
previous litter. Litters consisted of 1 or 2 kittens (
x
= 1.2, SD = 0.44, n = 13) at the
time they were found (Table 1). The sex ratio of ocelot kittens found in this study
was 1:2.5 (4 male, 10 female) (Table 1); however, there was no significant
difference (÷
2
1
= 2.57, p > 0.10) between the observed sex ratio and a 1:1 sex ratio.
All but 1 den site either occurred within close proximity (£ 10 m) to thornshrub
cover or were located directly under dense thornshrub cover. Three dens were
located in dense thornshrub brush and 1 den was located along a thornshrub
508 L. L. Laack et al.
Table 1. Breeding dates, birth dates, litter size, and sex ratio of ocelot (Leo-
pardus pardalis) litters found at Laguna Atascosa National Wildlife Refuge in
Cameron County, Texas, USA 1985–1997.
a
Based on gestation of 80 days prior
to date of birth (Cisin 1967, Eaton 1977, Fagen and Wiley 1978).
b
Pregnant
female was killed by a vehicle; date of birth was estimated based on fetal
development.
c
Based on denning patterns observed by females.
d
Heard kitten
in underground den but could not see kitten without destroying the dens site.
e
Observed female crossing road with 2 kittens, sexes not identified.
Adult female
ID number
Date of
breeding
a
Date of
birth
Date litter
observed
Observed litter
size and sex
ratio (M:F)
1 05/06/1985 25/08/1985 11/09/1985 0:1
2 06/09/1985 26/11/1985 19/12/1985 1:1
2 01/10/1987 20/12/1987 12/01/1988 0:1
2 26/08/1988 14/11/1988 02/12/1988 0:1
3
b
25/08/1986 15/11/1986 26/10/1986 1:1
4 23/07/1988 13/10/1988
c
–
4 01/03/1989 30/05/1989
d
– 1
5 25/02/1989 15/05/1989 25/05/1989 0:1
6 25/02/1989 15/05/1989 31/05/1989 1:0
7
b
10/04/1989 30/06/1989 25/06/1989 1:0
8 25/01/1991 15/04/1991
c
–
9 25/01/1991 15/04/1991 11/05/1991 0:1
10 15/06/1992 05/09/1992
c
10 14/03/1997 04/06/1997 18/06/1997 0:1
11 14/03/1997 04/06/1997 10/07/1997 0:1
12 25/02/1997 15/05/1997
c
29/09/1997 2
e
corridor with no vertical cover. Four dens were located in tussocks of alkalai
sacaton grass Sporobolus airoides and 2 in gulf cordgrass Spartina spartinae.
These sites were surrounded on at least 3 sides by thornshrub. Within dens, no
bedding was found and the den chamber usually consisted of grass bases of the
species described previously. Average dimensions of the den sites were 45 ´ 29 ´
30 cm. Thornshrub cover consisted of woody species described within the study
area.
Ten offspring of 7 resident female ocelots were monitored through daily visual
observations until 3 months of age. Eight of the 10 kittens survived until 3 months
of age. One kitten was killed by domestic dogs and the other died of unknown
causes. After 3 months of age, only 2 kittens were monitored until maturity,
whereas the other 6 kittens were not monitored beyond 3 months of age when they
left their den to begin traveling with their mothers.
The estimated survival rate of 3-month old ocelot kittens was 0.785 ± 0.13 SE.
We assumed ocelots over 3 months of age had the same 3-month survival rate as
resident ocelots (0.966). However, we assumed that survival of ocelot kittens
between 3 and 6 months of age was still dependant on their mother. Thus, we
assumed that ocelot kittens between 3 to 6-months of age had a 3-month survival
rate equal to their mothers 3-month survival rate (0.966) multiplied by their own
(0.966). Thus, ocelots aged 3 to 6-months of age had a survival rate of 0.933 (0.933
= 0.966 ´ 0.966). When an ocelot is ³ 6 months of age we assumed its 3-month
survival rate was 0.966, the same as a resident ocelot. Thus, we estimated that
first-year survival of an ocelot was S
^
= 0.68, or the product of S
^
= 0.785 ´ 0.933 ´
0.966 ´ 0.966.
Discussion
Parturition dates
Eaton (1977) found that captive ocelots breed through much of the year. In
addition, Eaton (1977) found that ocelots breed every year. Furthermore, captive
female ocelots have short inter-parturition periods if dependant kittens die at a
young age (Hatfield and Hatfield 1973, Eaton 1977). However, Emmons (1988)
suggested that wild ocelots had 2-year interbirth periods based on circumstantial
evidence. In this study, female 4 produced a litter 7 months following a successful
litter (Table 1), suggesting that wild ocelots have the potential for shorter
interbirth period than suggested by Emmons (1988). In addition, 1 wild Texas
female ocelot (female A) produced 3 litters within 15 months (Tewes 1986).
Unfortunately, female A was not monitored during her denning period and thus
no estimates of date of birth, date of breeding, date litter observed, or observed
litter size or sex ratio were estimated.
In October 1982, female A had a successful litter of at least 1 offspring (Tewes
1986). Eight months later she was recaptured and was lactating. Two months
later female A was captured again with evidence of post lactation with the
Reproductive history of Leopardus pardalis 509
offspring from the previous litter still using the maternal range (which it later
used as its own breeding range). Female A was again recaptured 3 months later
and was again in lactation. We believe the second litter of female A failed to
survive and that estrus occurred soon afterward.
Fecundity and sex ratio
Eaton (1977) found 1 to 3 kittens (
x
= 1.4 kittens) in 168 captive-born litters of
ocelots, with only 3 litters that contained 3 kittens. Previous observations of
free-ranging ocelots included 5 litters with 1 kitten, 3 litters with 2 kittens, and 1
litter with 3 kittens (Enders 1935, Vesey-FitzGerald 1936, Hall and Dalquest
1963, Petrides et al. 1951). Petrides et al. (1951) reported a pregnant female Texas
ocelot with 2 female fetuses, and the Smithsonian’s National Museum of Natural
History in Washington D.C. includes a pair of male kittens from a litter collected
by H. E. Bridgewater in 1956 in Kleberg County, Texas, and a solitary female
kitten collected by F. B. Armstrong in 1892 in Cameron County, Texas. Litters
consisted of 1 to 3 kittens (
x
= 1.4, SD = 0.58, n = 22) when our data was combined
with these historic observations.
When including all known records of litters, the cumulative sex ratio for the
ocelot in southern Texas was 1:2.2 (6 male, 13 female). However, there was no
significant difference (÷
2
1
= 0.33, p > 0.50) from a 1:1 sex ratio. Eaton (1977)
reported a sex ratio of 1:0.7 (n = 168) among captive-born ocelots.
Den ecology
All ocelot dens were devoid of prey remains and scat, much like dens sites of
the Florida panther Puma concolor coryi (Linnaeus 1771) (Maehr et al. 1989).
However, this was unlike bobcat Lynx rufus (Schreber 1777) dens that contained
numerous prey remains, other vegetation, and fecal marking stations (Bailey
1979).
Female ocelots usually used 2 to 4 den sites for each litter, and moved kittens 1
to 5 times. Females occupied den sites from 3 to 64 days (
x
= 27 ± 17 SD days/den
site, n = 16). Distance between consecutively occupied dens ranged from 110 to
280 m (
x
= 158 m ± 93 SD). However, this range excludes 1 female that moved
kittens 990 m. This long movement may have been in response to human
disturbance that consisted of brush clearing 40 m from the den site. Lions
Panthera leo (Linnaeus 1758), cheetahs Acinonyx jubatus (Schreber 1776), and
leopards Panthera pardus (Linnaeus 1758) occasionally relocate cubs to new dens
(Schaller 1972, Seidensticker 1977). Bailey (1979) suggested that female bobcats
may move young up to 6.5 km into areas that contained more prey. Ocelots in our
study relocated dens 0.11 to 0.28 km (excluding the female that responded to
human disturbance), making it unlikely that females moved dens in response to
prey availability. It is more likely that dens were moved because of the changing
needs of maturing kittens, or to move kittens away from a den site with
510 L. L. Laack et al.
accumulated odors and worn trails. Loss of concealment because of worn trails or
odor accumulation may expose litters to threats from other carnivores such as
coyotes Canis latrans (Say 1823), domestic dogs, bobcats, or conspecifics.
Female ocelots did not move kittens £ 3 days after the den was visited by
researchers, and females returned to their kittens £ 2 h after researchers exited
the den. Thus, human disturbance by researchers did not appear to cause den
abandonment or relocation.
Survival of young ocelots
This first year survival rate is comparable to first year survival rates cal-
culated by Hemker et al. (1986) S
^
= 0.67 and Logan and Sweanor (2001) S
^
= 0.64
for 0 to 1 year old mountain lion kittens in an unexploited population within arid
and semi-arid environments. Survival of 3-month old ocelot kittens did not differ
significantly (÷
2
1
= 2.07, p = 0.15) from a 3-month survival rate of resident ocelots.
Logan and Sweanor (2001) found that mountain lion kittens £ 3 months of age had
a higher rate of mortality than older cubs. Logan and Sweanor (2001) attributed
this higher mortality to the ability of predators able to detect trails made by
maternal mountain lions traveling in and out of the den to care for the young.
Ocelot reproductive adaptation and future research
The ocelot is primarily a tropical felid that breeds through the year (Eaton
1977, Mondolfi 1986, Nowell and Jackson 1996). Although the similarly-sized
bobcat residing in the southern portion of its range may breed year-round, it still
exhibits major parturition periods in late winter to early spring (Blankenship and
Swank 1979, Fritts and Sealander 1978, Winegarner and Winegarner 1982,
Wassmer et al. 1988).
Emmons (1988) believed that low fecundity, long gestation, and slow growth
periods in ocelots were adaptations to low expected rates of energy acquisition. In
addition, these characteristics typify other small to medium-sized Neotropical
cats such as the oncilla Leopardus tigrinus (Schreber, 1775) (Fagan and Wiley
1974, Quillen 1981, Widholzer et al. 1981) and margay Leopardus wiedii (Schinz,
1821) (Fagan and Wiley 1974, Eaton 1984, Mellen 1993). However, in southern
Texas, ocelots have the potential for 1- year interbirth periods while evidence
suggests that ocelots in the tropics have 2 year inter-birth periods (Emmons
1988). This may be the result of ocelots within southern Texas having higher rates
of energy acquisition compared to ocelots in the Neotropics. However, this has yet
to be analyzed.
We believe these findings contribute to an understanding of ocelot re-
productive ecology and provide the best available estimates of fecundity and
first-year survival that can be used in population modeling. However, more
research is needed to obtain estimates of ocelot kitten survival, juvenile survival,
and sources of mortality. In addition, we recommend more research on interbirth
Reproductive history of Leopardus pardalis 511
periods and any possible relation to energy acquisition. Furthermore, the majority
of these data are over 10 years old, and the LANWR population is small and
isolated. Thus, current research is needed to analyze potential negative effects of
inbreeding or habitat fragmentation on ocelot reproductive life history.
Acknowledgements: This project was funded by the Rob and Bessie Welder Wildlife Foundation, U.S.
Fish and Wildlife Service, the James R. Dougherty Foundation, the Ben and Rachael Vaughen
Foundation, the Boone and Crocket Club, G. Hixon, and B. Vaughan, III. We thank personnel from
the LANWR for granting permission to use the land. We also thank L. Drawe, D. Everett, M.
Fernandez, E. Haines, J. Janecka, S. Jojola, J. Mays, S. Miller, 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
University of Idaho for their support facilities, and S. Henke and W. Kuvlesky for reviewing this
manuscript. This is publication #04-119 of the Caesar Kleberg Wildlife Research Institute and
Contribution #637 of the Rob and Bessie Welder Wildlife Foundation.
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Received 28 October 2004, accepted 14 April 2005.
Associate Editor was Joseph F. Merritt.
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