Factors affecting habitat patch use by sloth bears in Mudumalai Tiger Reserve, Western Ghats, India Tharmalingam Ramesh1, Riddhika Kalle1, Kalyanasundaram Sankar1,2, and Qamar Qureshi1 1Wildlife Institute of India, PO Box 18, Chandrabani, Dehra Dun-248 001, Uttarakhand, India Abstract: Of the threats facing sloth bear (Melursus ursinus) populations, habitat fragmentation is the most pressing. Although conservation requires protection of habitat, little is known about the factors governing sloth bear occurrence. We used camera-trapping data to investigate occupancy of sloth bears in Mudumalai Tiger Reserve, an important conservation site in India during January–April 2010. Presence–absence data, collected under a systematic sampling framework, were used to test a priori hypotheses incorporating covariates believed to influence sloth bear occurrence. The estimated occupancy of sloth bears in the study area was 0.83 (SE 5 0.01) with a detection probability of 0.23 (SE 5 0.07). We found that no model with covariates was as strongly supported as the null model, suggesting that covariates we chose were relatively weak predictors of use. That said, our results suggested that sloth bear use was associated with deciduous forests; weaker evidence was found for association with termite mounds and fruiting trees. In the future, monitoring programs for wide-ranging species could benefit from using occupancy surveys. Key words: camera trapping, detection probability, habitat use, Melursus ursinus, sloth bear, Western Ghats Ursus 23(1):78–85 (2012) Sloth bears (Melursus ursinus) are widely distrib- useful technique for obtaining data on carnivores uted in India with an estimated population size such as sloth bears (Karanth and Nichols 1998, between 6,000 and 11,000. However, only about 10% Carbone et al. 2001) which are nocturnal, elusive, of good quality sloth bear habitat is left in India. solitary, and occur in dense forest (Ramesh 2010, (Yoganand et al. 2006). The sloth bear now exists in Gopalaswamy 2006). Camera-trapping techniques fragmented populations that face continuing threats within a robust capture–recapture framework have from habitat deterioration and poaching (H.S. been effective on other species of bears (Noyce et al. Singh, 2001, Regional planning for sloth bear 2001, Mace et al. 1994, Rı´os-Uzeda et al. 2007, (Melursus ursinus) conservation in the western India, Matthews et al. 2008). This method has the advan- Gujarat Ecological Education and Research Foun- tage of sampling more individuals over a larger dation, Gandhinagar, India), with timber and fire- spatial scale than is normally possible with radio- wood harvesting causing extensive habitat loss collaring studies. (Servheen 1990). Their diets are largely based on Habitat use by mammals is largely shaped by a fruits and termites but vary seasonally and geo- range of factors to suit their biological requirements graphically across their range from Nepal south (Seidensticker 1976, Wrangham and Rubenstein through India and Sri Lanka, (Baskaran 1990, 1986). Occurrence can be modeled as a function of Gopal 1991, Gokula et al. 1995, Yoganand et al. measured habitat covariates, allowing for testing of 2006, Ramesh et al. 2010). hypotheses on species–habitat relationships (MacK- Sloth bear habitat use has been described based on enzie et al. 2002). Studies that quantify habitat use radiocollared individuals (Joshi et al. 1995, 1999; by a species can predict effects of habitat changes Yoganand et al. 2005; Ratnayeke et al. 2007), den and justify protection for key areas (Carey et al. site observations, and indirect evidence (Baskaran 1992). 1990, Desai et al. 1997, Akhtar et al. 2004, Chauhan Sloth bears are reported to exist in 174 protected et al. 2004). However, camera–trapping is also a areas in India (Chauhan 2006); however, their eco- logy and distribution is poorly understood, so there [email protected] is little scientific basis underlying conservation 78 HABITAT PATCH USE BY SLOTH BEARS N Ramesh et al. 79 strategies. The prospects for persistence of sloth (39.6 km2). Mudumalai Tiger Reserve received bears in protected areas need to be evaluated with rainfall from the southwest monsoon which starts in rigorous comprehensive field studies. Protected areas May and ends in August and the northeast monsoon in deciduous habitat contain large contiguous forests which starts in September and ends in December. that support high populations of sloth bear, while in Average annual rainfall had a marked east–west other regions of India, populations mostly occur in gradient from 600 mm in the northeast to 1800 mm in low abundance (Yoganand et al. 2006). The Western the southwest. Based on the climate of the area, there Ghats are a stronghold of sloth bear distribution, in were 3 distinct seasons: dry season (Jan to Apr), first terms of population abundance and habitat viability wet season (May to Aug), and second wet season (Sep (Yoganand et al. 2006). Therefore, it is crucial to to Dec; Varman and Sukumar 1995). Mean temper- develop systematic methods to allow sloth bears to ature ranged from 15.7uC to 28.7uC between Novem- be more fully assessed for their probable threatened ber and April. The variability in forest structure and status through monitoring programs incorporating the degree of deciduousness in the dry forests was a detection probability that lead to unbiased estimates function of moisture availability and anthropogenic of habitat effects or misleading inferences about disturbance (Pascal 1986). Forest fires, natural and the species distribution (Tyre et al. 2003, Gu and anthropogenic, occurred annually, sweeping across Swihart 2004). large areas in Mudumalai. These forests were also With this goal, we applied a rigorous statistical subject to major proliferation of invasive plants such approach to model site occupancy and detection as Lantana camara, Eupatorium odoratum, Parthe- probability based on mark–recapture theory (Mac- nium hysterophorus, and Opuntia dillenii. Other large Kenzie et al. 2002). We estimated the probability that carnivores present are tiger (Panthera tigris), leopard a site is usable (i.e. that a species may use the site), (Panthera pardus), dhole (Cuon alpinus), and striped which we define here as occupancy (y). We aimed hyena (Hyaena hyaena). Domestic livestock (cattle, to use camera trap data to determine sloth bear buffalo and goats) occurred in village areas inside the occupancy as a function of various site variables Tiger Reserve. hypothesized to influence the probability of occupan- cy in Mudumalai Tiger Reserve. The main objectives of this research were to (1) establish a reliable estimate Methods of sloth bear occupancy in Mudumalai Tiger Reserve, Camera trapping and (2) identify the factors affecting sloth bear habitat We deployed heat-in-motion sensor 35-mm film use. This information is likely to provide basic camera traps, DEERCAM DC300 (Non Typical, ecological data to facilitate appropriate conservation Inc., Park Falls, Wisconsin, USA) in 3 study sites of management for sloth bears in India. Mudumalai Tiger Reserve. Camera-trap data pre- sented here were obtained during a study on sym- patric large carnivores (tiger, leopard, and dhole) in Study area Mudumalai Tiger Reserve (Ramesh 2010, Kalle Our study was conducted in Mudumalai Tiger et al. 2011). Twenty trap stations were operated in Reserve (11u329–11u439N; 76u229–76u459E) within the deciduous forest (107 km2) from 1 January to 9 Nilgiri Biosphere Reserve of South India. Mudumalai February, 13 in dry-thorn forest (39.2 km2) from 19 was situated at the junction of the 3 states of Tamil February to 20 March, and 17 in the semi-evergreen Nadu, Karnataka, and Kerala with Wayanad Wildlife forest (39.6 km2) from 27 March to 25 April 2010 Sanctuary on the west, Bandipur Tiger Reserve in the (Table 1). Cameras were deployed systematically in north, and the Nilgiri North Forest Division in the stations that maintained an average inter-station south (Fig. 1). The topography was undulating, inter- distance of 1.8 km to cover the study sites without spersed with hills and plateaus. Elevation varied from leaving any large gaps in the trap array (gaps may 960 to 1,266 m. The reserve spanned 321 km2 of dry have resulted in 0 detection probability for sloth thorn, dry deciduous, moist deciduous, semi-evergreen, bears actually present). Cameras were active 24 hr/ moist bamboo brakes, and riparian fringe forests day, with a 30-second delay between consecutive (Champion and Seth 1968). We sampled 3 intensive photographs, and the sensitivity of the motion sen- study sites comprising deciduous forest (107 km2), dry- sor was set to high. Each camera-trap station com- thorn forest (39.2 km2) and semi-evergreen forest prised a pair of cameras to maximize capture Ursus 23(1):78–85 (2012) 80 HABITAT PATCH USE BY SLOTH BEARS N Ramesh et al. Fig. 1. Locations of camera trap stations for a study of sloth bears in Mudumalai Tiger Reserve, Western Ghats, India, Jan–Apr 2010. probability of sloth bears. Cameras were placed trapping duration was divided into 10 sampling approximately 35 cm above the ground and 5–8 m occasions of 4 days each for further analysis. away from the center of the trail. Cameras were placed on roads, trails, stream-beds, or near water Habitat measurements holes to maximize sloth bear photo captures. We measured habitat features in 20-m diameter Photographs provided information on the date and plots centered at each camera station. The number time of the picture taken. Camera-trap stations were of fruiting trees (.1 cm diameter at breast height visited every week to replace film and check their [DBH] and .1 m height) and active termite mounds maintenance. Although some cameras were damaged were counted, and the cover of fruiting shrubs (,1cm by elephants (Elephas maximus), we replaced them DBH and ,1 m height) was estimated as ,25%, 26– with new ones to avoid loss of data.