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European Journal of WildlifeResearch ISSN 1612-4642 Eur J Wildl
ResDOI 10.1007/s10344-014-0822-3
Reproductive characteristics of femaleBengal tigers, in
Ranthambhore TigerReserve, India
Randeep Singh, Qamar Qureshi,Kalyanasundaram Sankar,
PaulR.Krausman & Surendra Prakash Goyal
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ORIGINAL PAPER
Reproductive characteristics of female Bengal tigers,in
Ranthambhore Tiger Reserve, India
Randeep Singh & Qamar Qureshi &Kalyanasundaram Sankar
& Paul R. Krausman &Surendra Prakash Goyal
Received: 25 March 2014 /Accepted: 15 April 2014#
Springer-Verlag Berlin Heidelberg 2014
Abstract Reproductive characteristics of tigers (Pantheratigris)
are important to understand population viability. Westudied the
reproductive parameters of female Bengal tigers(P. t. tigris) in a
dry, tropical, deciduous habitat inRanthambhore Tiger Reserve
(RTR), western India, fromApril 2005 to March 2010. We monitored
tigers by directobservation and with cameras placed throughout
their habitat.The potential breeding population included 13 adult
females.The average age at first reproduction was 3.3 years; 34
cubswere born during the study period (6.20.82 per year). Sixty-six
percent of the births occurred between October and De-cember. Mean
litter size was 2.260.52 (n=13, range=13).The sex ratio of 32 cubs
was 1.29 M:1.00 F. The survival rateof cubs (3 years old. Only 2 of
the 13 femalesreproduced twice during the 5 years of the study. The
birthinterval was 33.43.7 months (range 2465 months). Themean
reproductive rate was 0.590.23 cubs/female/year.Our study indicates
that tiger populations can grow rapidly ifthe habitat provides
adequate protection, an adequate popula-tion of prey, and minimal
to no poaching.
Keywords Camera trap . Litter size . Mortality .Pantheratigris
tigris . Sex ratio . Survival
Introduction
Reproductive success is a key to survival and continued
exis-tence for any species, and understanding species
reproductiveparameters (e.g., age at first reproduction,
reproductive rate,liter size, interbirth interval, and breeding
period) is critical todeveloping effective conservation strategies
(Carter et al.1999). Reproductive parameters are important to
determinepopulation turnover, potential growth rates, and are
importantindicators to detect the lineage persistence in a
population (i.e.,lineage loss, individual fitness, population
viability [Kelly2001; Holt et al. 2003]), population viability
(Kelly 2001;Balme et al. 2012), and to examine meta-population
dynamics(e.g., determining the reproductive output of source
popula-tions; Smith and McDougal 1991; Chapron et al. 2008).
Reproductive data are available for some long-lived carni-vores
(i.e., lions Panthera leo; Packer et al. 1988), cheetahs(Acinonyx
jubatus; Kelly et al. 1998); leopard (Pantherapardus; Balme et al.
2012), and pumas (Puma concolor;Logan and Sweanor 2001). Yet
reproductive parameters ofwild tiger (Panthera tigris) populations
are sparsely availableand may vary over their global range. The
limited informationon reproductive parameters has been obtained
from studies inIndia (Schaller 1967; Sankhala 1978; Chundawat et
al. 2002;Singh et al. 2013a), Nepal (Sunquist 1981; Smith
andMcDougal 1991; Smith 1993), and the Russian Far East(Smirnov and
Miquelle 1999; Kerley et al. 2003). Reproduc-tive parameters may
vary among the subspecies of the popu-lations because of the
different climatic conditions, habitats,prey densities, and other
environmental parameters (Kerleyet al. 2003). Information on how
reproductive parameters varyamong subpopulations of the same
subspecies surviving indifferent habitats is essential for
range-wide conservationplanning (Kerley et al. 2003).
We present reproductive data collected from 2005 to 2010on a
protected tiger population in the dry, tropical habitat of
Communicated by C. Gortzar
R. Singh (*) :Q. Qureshi :K. Sankar : S. P. GoyalWildlife
Institute of India, Post Box # 18,Dehradun 248 001, Uttarakahnd,
Indiae-mail: [email protected]
P. R. KrausmanBoone and Crockett Program in Wildlife
Conservation,University of Montana, Missoula 59812, USA
Eur J Wildl ResDOI 10.1007/s10344-014-0822-3
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Ranthambhore Tiger Reserve (RTR), Rajasthan India. Thepopulation
in RTR represents a unique gene pool (Sharmaet al. 2008), which is
adapted to survive harsh and inclementweather conditions during
summer. The open, thorny, decid-uous forest with scanty vegetation
and a good road network inRTR provided ideal conditions for tiger
sightings (particularlyin the valley and other low-lying areas).
Geographic closure ofthe population and easy accessibility provided
an opportunityto monitor reproduction through a combination of
direct ob-servations and camera trapping. We used an extensive
datasetcompiled on tigers (Singh et al. 2013a, b) to establish
baselineinformation on reproductive parameters and enhance the
un-derstanding of tiger reproductive ecology to facilitate
theconservation to improve management strategies for
thespecies.
Materials and methods
Study area
The study was conducted in RTR (25 54 to 26 12 N, 7622 to 76 39
E), in Sawai Madhopur district of Rajasthan,India. Intensive data
collection was undertaken in the corezone (392 km2). The RTR is
located on the Aravalli andVindhya hill ranges. The region received
an average annualrainfall of 800 mm, and temperatures were as low
as 2 C inJanuary and as high as 47 C in May. The vegetation of
RTRcorresponded to those of northern tropical, dry,
deciduousforests and the northern tropical thorn forest (Champion
andSeth 1968). The vegetation of RTR is representative of atypical,
dry, and deciduous dhok (Anogeissus pendula) forest.Apart from
dhok, the other species commonly found arekadaya (Sterculia urens),
salai (Boswellia serrata), raunj(Acacia leucophloea), amaltas
(Cassia fistula), palash (Buteamonosperma), tendu (Diospyros
melanoxylon), gurjan(Lannea coromandelica), and jamun (Syzigium
cumini).Ranthambhore was characterized by a subtropical dry
climatewith four distinct seasons as follows: winter
(DecemberFeb-ruary), summer (MarchJune), monsoon
(JulySeptember),and post monsoon (OctoberNovember). Carnivores
in-cluded tigers, leopards (P. pardus), sloth bears
(Melursusursinus), and striped hyaenas (Hyaena hyaena). The
RTRsupported five species of wild ungulates, including the
chital(Axis axis), sambar (Rusa unicolor), nilgai
(Boselaphustragocamelus), chinkara (Gazella gazelle), and wild pig
(Susscrofa).
Camera trapping
An intensive camera trapping study was conducted in the corearea
of RTR in 2005 (Chauhan et al. 2005) after the decline ofthe tiger
population from unknown causes in 2004 (S. P.
Goyal, personal observation). During 2005, the tiger popula-tion
in RTR consisted of 19 individual tigers (4 M, 10 F, and 5cubs [3 M
and 2 F 1 month in a camera trap, we attempted toobserve them on
foot patrols during the day and at night (usingsearch lights in a
vehicle near water points and roads). Themonitoring of tigers in
RTR provided information about the
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reproductive characteristics of female tigers including
theproportion of females that reproduce each year, annual
birthrate, age at first reproduction, seasonality of birth,
meaninterval between litters, mean litter size, recruitment
rate,cub mortality, sex ratio of litters, and cub age at
dispersal,emigration, immigration, and mortality.
We used the following age categories (Karanth 2003): cubs(1 year
old, associated with, and dependent on theirmothers), juveniles (2
years old), subadults or post dispersalfloaters or transients
(>2 years old, no longer associating withtheir mothers but not
reproducing), and breeding adults
(3 years old). The proportion of females (3 years old) thathad
reproduced was based on direct observations and photo-graphic
evidence from camera traps.
Breeding time and litter monitoring
We assumed that breeding occurred if we observed lactatingtigers
or could estimate the breeding time based on the ap-pearance of
cubs. We did not have any radio-collared individ-ual that gave us
actual information, breeding month of femaletiger, and when cubs
start moving with the mother. Thus, we
Fig. 1 Area of intensive sampling in Ranthambhore Tiger Reserve,
India using camera traps 20052010
Table 1 Sampling efforts from April 2005 to March 2010 in
Ranthambhore Tiger Reserve, India
S.N. Season Duration Sampled area (km2) No. camera trapping
station Trapping days Trap nights No. photo-captures
1. Summer Apr-05 to May-05 160 30 60 358 31
2. Winter Oct-06 to Mar-07 140 106 226 3,380 110
3. Winter Nov-07 to Feb-08 233 224 80 4,480 173
4. Summer Apr-08 to Jun-08 233 167 60 3,340 76
5. Post monsoon Oct-08 to Nov-08 233 140 60 2,800 137
6. Winter Jan-09 to Mar-09 233 194 60 3,880 206
7. Summer Apr-09 to Jun 09 233 178 60 3,560 163
8. Post monsoon Oct-09 to Dec-09 233 181 60 3,620 128
9. Winter Jan-10 to Mar-10 233 165 60 3300 122
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used backdating following published studies on tiger to
esti-mate the breeding month of female tigers by backdating2 months
from the first appearance of cubs because cubs startmoving with the
mother when 2 months old (Smith et al.1987; Majumder et al. 2012).
Litters were divided into fourdifferent seasons based on birth
dates winter (DecemberFebruary), summer (MarchJune), monsoon
(JulySeptember), and post monsoon (OctoberNovember).
Therefore, once cubs were captured in a camera trap, wemade an
intensive effort to observe litter size through pug-marks on the
road, by direct sighting, or photo-capture in othercamera traps. We
compiled the photographic data set of tigercubs starting from 2
months through 36 months and wecompared the photo-capture of cubs
with our data setand estimated the approximate age of the cubs. The
tigerpopulation, including cubs, was monitored throughout theyear
(Table 1). We sexed animals as they aged andmatured based on size
differences between male and fe-male siblings. Sex of cubs was
identified by a combina-tion of opportunistic sightings and
photographs obtainedthrough camera traps or by observing their
genital inphotographs. The open, thorny, deciduous forest
withscanty vegetation and a good road network in RTR pro-vided
ideal conditions for tiger sightings. When monitor-ing tigers, we
often encountered females with cubs and wespent 13 h in a
particular place to observe the behaviorand activity of females and
their cubs, which strengthenedour data to identify more accurately
the sex of the cubs.In addition to camera traps, it provided an
opportunity forus to know more accurately the liter size and sex of
cubs.The sex of cubs was estimated after they were >12
monthsold.
Reproductive rate
We determined the proportion of females that reproduced
eachyear, annual birth rate, mean individual birth rate, and
recruit-ment rate. The proportion of breeding females that
reproducedeach year was recorded through intensive monitoring
usingcamera traps, intensive searches (i.e., foot patrolling in
dayand night patrolling using search lights and vehicles)
oppor-tunistic sighting, and pugmarks. The annual birth rate
wasestimated as the number of cubs produced by all femalesdivided
by the number of females in the population(>3 years; Persson et
al. 2006). The annual mean proportionof breeding females producing
cubs was calculated using themethod described by Persson et al.
(2006). To estimate thelifetime productivity of individual tigers,
the reproductivelyactive age of females was calculated (i.e.,
tigers were repro-ductively active from 4 to 14 years of age;
Crandall 1964;Kleiman 1974; Nowell and Jackson 1996) and multiplied
bythe mean annual birth rate.
Estimation of survival rate at different ages
The percentage of tigers alive was divided into stages:12 month
old, juveniles (12 to 24 months old), and post-dispersal floaters
or transients (>24 month old). Tiger cubsstart moving with their
mother when they are 2 months old,and tracks of 34-month-old cubs
were regularly seen withthose of the mother. Cubs frequently remain
with the motheruntil they were 1824 months old (Smith 1993).
Survival ofcubs 4 times/month until the cubs were12 months old to
estimate the number of cubs that survived.Survival between the ages
of 1224 and >24 months (dispers-al age) was determined through
photo capture of individualsby camera traps and continuous
individual-based monitoringprotocol (Singh 2011). We used the
KaplanMeier methodwith a staggered-entry design (Pollock et al.
1989) to estimatethe survival rates of cubs of the different age
classes. Wepooled data from all years to obtain a sufficient sample
size.Confidence intervals (95 %) for survival rates were
derivedaccording to Pollock et al. (1989).
Results
Sampling efforts
Camera traps were operated for from April 2005 to March2010 (726
days, 28,718 trap nights over 3 different seasons,1,231
photo-captures of tigers; Table 1).
Breeding population and productivity
During the study period, 13 breeding females were identifiedby
camera traps and monitored. All 13 females gave birth atleast once,
and 2 females gave birth twice during the studyperiod (15 litters;
Table 2). The minimum number of breedingfemales in a year was 2,
and the maximum was 5 (Fig. 2). Wedid not document any litter in
2009. Two of 13 females weremonitored from birth, and they
reproduced for the first time at33 and 48 months. Two females bred
twice, and the periodbetween successive births was 24 and 65
months. The meaninterbirth interval was 33.43.7 months.
Birth period, litter size, and sex ratio
The mean litter size was 2.260.39 (n=15, range=13).There were
three cubs in five of the litters, two cubs in ninelitters, and one
cub in one litter (Table 3). One female raisedfive cubs (1 M and 4
F) in two litters. Of 34 cubs from 15litters, we recorded the sex
of 32 cubs produced by 12
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breeding females. There was no significant difference in thesex
ratio of cubs at birth, although it was slightly male biasedwith
1.29 M:1.00 F (2=1.82, df=3; P=0.61). Ten breedingfemales gave
birth to more males than to females (Fig. 3). Ourdata suggested
that most of the litters were born in early and latewinter (n=15
litters from 13 mothers). Most births reported inthe post monsoon,
27 % in winter, and 6 % in monsoon. Nobirths were reported during
summer (Fig. 4).
Reproductive rate
Twenty-seven individual tigers 4 years old (11 F and 16
M)survived until March 2010. The annual mean proportion offemales
producing cubs was 0.260.08 and ranged from 0.15to 0.63 (Table 4).
The mean annual birth rate was 0.590.23
cubs/female (Table 4). Assuming a female is reproductivelyactive
from 4 to 15 years of age, the total lifetime productivitywould be
6.49 cubs/breeding female in RTR.
Mortality and survival rate of cubs
Cubs died due to several causes (Table 3). The survival rate
ofcubs
- 0.610.91; n=29; Table 5). Two juvenile males survived>1 year
and died when
- tigers in the Russian Far East gave birth all through the
year,most frequently in late summer (AugustOctober, >50 %),which
indicates that conceptions are most frequent duringMarchMay (Kerley
et al. 2003). Data on 530 litters of Amurtigers born in zoos in the
northern hemisphere indicate thatmost cubs are born between April
and June (Seal et al. 1987).Our findings on the breeding period of
the tiger in the tropical,dry, deciduous habitat differ from those
reported by Smith andMcDougal (1991) and Smith (1993) who indicate
that thebirthing peak of the tiger in the Indian subcontinent is in
thesummer (AprilJune). In RTR, most parturition (93 %) oc-curred in
post monsoon and winter (OctoberFebruary). Itmay be due to the
influence of harsh climatic conditionsduring summer and the low
annual precipitation (
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populations, genetic integrity and loss of genetic diversityover
time may be minimized if the population growth andsurvival are not
hindered and are monitored.
Conservation implication
Dry, tropical deciduous forests in southeastern Asian
countriesare fragile ecosystems due to low productivity and
unpredict-able climatic conditions. They are prone to forest
fragmenta-tion and habitat loss due to developmental activities
(Sodhiet al. 2004). The population surviving in these
fragmentedhabitats may have varied rate of reproductive success
that mayaffect genetic diversity, especially when populations are
small(ca ~50 individuals; Berger and Cunningham 1995). There-fore,
it is crucial to monitor changes in demography andreproductive
parameters. Our study provides insight into thereproductive
parameters of female tigers inhabiting semiaridregions in western
India. We suggest that there should beminimum disturbance to tigers
during mating (monsoon andpost monsoon) and parturition (post
monsoon and winter).The cub survival rate in RTR is high, so we
suggest thatcontinuous monitoring of tiger populations may generate
aclearer picture of the mortality, dispersal, and breeding of
thissmall and isolated population. Because the existing corridorsin
RTR are not functional (Singh et al. 2013b), we recommendthe
identification of dispersal corridors and restoration
ofconnectivity that may help the long-term persistence of tigersin
this semiarid landscape. The information we generated forthe first
time for semiarid habitats in India through a long-termstudy will
be useful to enhance our understanding of thereproductive behavior
of tigers and used as baseline informa-tion for comparison in the
future to form part of the manage-ment effectiveness evaluation
process implemented by theNational Tiger Conservation Authority,
Government of India(Mathur et al. 2014).
Acknowledgments We thank the Director and Dean of the
WildlifeInstitute of India for their support. We thank the
Rajasthan ForestDepartment and the reserve officials and field
staff at RTR forpermissions and for facilitating this work. We
especially thank natureguides of RTR and our field assistants, M.
S. Gurjar and S. Sharma,for providing support. The Wildlife
Institute of India, Dehra Dunprovided financial support for the
project. We are also thankful tofour anonymous reviewers who have
provided their valuable sug-gestion and comments on an earlier
draft.
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Reproductive characteristics of female Bengal tigers, in
Ranthambhore Tiger Reserve, IndiaAbstractIntroductionMaterials and
methodsStudy areaCamera trappingMonitoring female tigers and their
reproductive characteristicsBreeding time and litter
monitoringReproductive rateEstimation of survival rate at different
ages
ResultsSampling effortsBreeding population and productivityBirth
period, litter size, and sex ratioReproductive rateMortality and
survival rate of cubs
DiscussionConservation implication
References
