Activity pattern of Sloth Bear Melursus ursinus (Mammalia: Ursidae) in Mudumalai Tiger Reserve, Western Ghats, India
Tharmalingam Ramesh 1, Riddhika Kalle 2, Kalyanasundaram Sankar 3 & Qamar Qureshi 4
1–4 Wildlife Institute of India, P.O Box # 18, Chandrabani, Dehradun, Uttarakhand 248001, India
1 firstname.lastname@example.org (corresponding author), 2 email@example.com,
3 firstname.lastname@example.org, 4 email@example.com
Activity patterns are shaped largely by the biological requirements of a species (Wrangham & Rubenstein 1986). Activity patterns in mammals can be influenced by foraging, prey behaviour, predator avoidance, physiological traits, vegetation cover and climate (Seidensticker 1976). The activity patterns of Sloth Bears have been described based on radio-collared individuals (Joshi et al. 1995, 1999; Yoganand et al. 2005; Ratnayeke et al. 2007), den site observations and indirect evidences (Baskaran 1990; Desai et al. 1997; Akhtar et al. 2004; Chauhan et al. 2004). Sloth Bears are known to be nocturnal and crepuscular in activity (Chauhan et al. 2004; Yoganand et al. 2005). The protected areas of deciduous forests hold large forest tracts and contiguous forests that support a considerable population of Sloth Bear while in other forest types, populations mostly occur in low abundance in India (Yoganand et al. 2006). The Western Ghats range is one of the strongholds of Sloth Bear distribution, in terms of both population abundance and habitat availability in India (Yoganand et al. 2006). Mudumalai is one of the few tropical forests in the Western Ghats where the Sloth Bear is widely distributed (Desai et al. 1997; Ramesh et al. 2010, 2012) and thrives in dense forest areas (Yoganand et al. 2006). Camera trapping provides valuable ecological information on these species and has its own advantage that includes capture of more number of individuals at a spatial scale which is a limitation in radio-collared studies (Ramesh 2010). However, use of information from systematic camera trapping surveys to study activity patterns remains rare (Gopalaswamy 2006). Here we used camera trapping technique as a useful tool to study activity patterns of Sloth Bears.
Materials and Methods: Mudumalai Tiger Reserve (11032Õ–11043ÕN & 76022Õ–76045ÕE) is situated at the tri-junction of the southern Indian states of Tamil Nadu, Karnataka and Kerala at an elevation that varies from 960–1,266 m. This 321km2 reserve is bound by Wayanad Wildlife Sanctuary on the west, Bandipur Tiger Reserve in the north, and in the south and east by Sigur and Singara forest divisions. The vegetation types found in Mudumalai are classified into southern tropical dry thorn forest, southern tropical dry deciduous forest, southern tropical moist deciduous forest, southern tropical semi-evergreen forest, moist bamboo brakes and riparian forest (Champion & Seth 1968). The terrain is gently undulating. It receives rainfall from both the south-west monsoon between May and August and the north-east monsoon between September and December. Three distinct seasons are recognized; dry season (January–April), first wet season (May–August) and second wet season (September–December) (Varman & Sukumar 1993). The rainfall has a marked east-west gradient, with the areas in the east getting the least amount of the heavy rains (1000–2000 mm). The mean temperature ranges from 15.7–28.7 0C between November and April. Other large carnivores found in the Reserve are Tiger Panthera tigris, Leopard Panthera pardus and Dhole Cuon alpinus.
Camera traps were deployed (November 2009 to April 2010) as part of the research on sympatric large carnivores—Tiger, Leopard and Dhole—within an intensive study area of 187km2 covering deciduous forest (DD), semi-evergreen forest (SE) and dry thorn forest (DT) of Mudumalai Tiger Reserve (Fig. 1). Cameras were deployed systematically in stations that maintained an average inter-station distance of 1.8km to cover the study sites without leaving any large space in the trap array for Tiger, Leopard and Dhole. However, Sloth Bears are known to have home ranges of even more than 30km2 (Yoganand et al. 2005) and we believe that this spacing will allow inclusion of many spatially distributed unique individual Sloth Bears in the study area. The camera stations were placed on roads, trails, stream-beds or near water holes to maximize bear photo captures. According to the available extent of the major forest types, we set up 20 trap stations for 70 days in deciduous habitat, and 17 and 13 trap stations for 40 days in semi-evergreen and dry thorn forest respectively on a 24hr basis. Each station comprised of two pairs of passive infrared cameras to maximize Sloth Bear capture probability. Cameras were loaded with 36-print, 200 American Standard Association (ASA) 35mm film. The event of capturing an individual Sloth Bear, photographed by single or both camera traps, was considered to be an independent record of that species based on time and trap location. Both sides of an individual animal and duplicate photographs of the same animals were taken during a short period of time (<30 seconds) however, only one photo was considered as an independent photo for further analysis. The percentage of activity level was used to indicate whether the study species was nocturnal or diurnal. Time of capture was used to create 24-hr activity patterns of Sloth Bear. Photographs provided information on the date and time of the picture taken and were used to establish the activity pattern of Sloth Bear. Photographs were sorted out into two hour time intervals to examine activity pattern. The mean activity of Sloth Bear was quantified by WatsonÕs U2 test using program Oriana 3.21 (Kovach 2009).
Results: Totally, 61 independent photographs were obtained from 2600 trap nights. Sloth Bears showed bimodal peaks in their activity; the first peak was observed from late evening to midnight and another small peak in the early morning during sunrise. Though Sloth Bears were active throughout the day they exhibited reduced activity during the hottest hours of the day (Fig. 2). The mean activity time was 21:54±00:46 hrs (95% CI 20:23–23:25, WatsonÕs U2 test, p<0.01).
Discussion: Several authors observed that though Sloth Bears were active throughout the day, they were mostly nocturnal and crepuscular (Chauhan et al. 2004; Yoganand et al. 2005) and active during the evening and night (Joshi et al. 1999). In the present study, Sloth Bears showed more activity during late evening to midnight, and early mornings. They were less active during the mid day. Sloth Bears may have reduced their activity during the day to avoid the intense heat. Day-resting habits by Sloth Bears have been reported from long-term radio-telemetry studies in Panna National Park where bears were observed resting in dense undergrowths, often in gaps between large boulders and inside caves during intense heat in the dry season (Yoganand et al. 2005). Similar habits of Sloth Bear may prevail in Mudumalai which may have resulted in their low captures during mid-day (11–15 hr). However, activity pattern may vary depending on geographical location, climate, distribution of food resources, interaction with other species, human disturbance and other factors (Yoganand et al. 2005). Some of the differences observed in activity patterns among sites could result from different methodologies used to study the species. Camera trapping has proved to be a useful complement to telemetry study in documenting 24hr temporal activity pattern of Sloth Bear. Camera trapping can augment the details of spatio-temporal patterns of multiple individuals simultaneously with less effort than telemetry study. Our data demonstrate that use of camera-traps in documenting activity patterns can be an effective tool for identifying biological questions in depth to document Sloth Bear ecology for future studies.
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