Identifying Regions for Conservation of Sloth Bears Through Occupancy Modelling in North-Eastern Karnataka, India
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Identifying regions for conservation of sloth bears through occupancy modelling in north-eastern Karnataka, India Sayantan Das1, Saurav Dutta2, Sharmi Sen3, Jijumon A. S.2, S. Babu4, Honnavalli Nagraj Kumara4, and Mewa Singh1,5,6 1Biopsychology Laboratory and Institution of Excellence, University of Mysore, Manasagangotri, Mysore-570006, Karnataka, India 2Indian Institute of Science Education and Research-Kolkata, Mohanpur Campus, Post: BCKV Main Office, Mohanpur, Nadia-741252, West Bengal, India 3Indian Institute of Science Education and Research-Mohali, Knowledge City, Sector 81, SAS Nagar, Manauli-140306, Punjab, India 4Sa´lim Ali Centre for Ornithology and Natural History, Anaikatty, Coimbatore-641108, Tamil Nadu, India 5Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, Karnataka, India Abstract: In the absence of information on species in decline with contracting ranges, management should emphasize remaining populations and protection of their habitats. Threatened by anthropogenic pressure including habitat degradation and loss, sloth bears (Melursus ursinus) in India have become limited in range, habitat, and population size. We identified ecological and anthropogenic determinants of occurrence within an occupancy framework to evaluate habitat suitability of non-protected regions (with sloth bears) in northeastern Karnataka, India. We employed a systematic sampling methodology to yield presence–absence data to examine a priori hypotheses of determinants that affected occupancy. These covariates were broadly classified as habitat or anthropogenic factors. Mean number of termite mounds and trees positively influenced sloth bear occupancy, and grazing pressure expounded by mean number of livestock dung affected it negatively. Also, mean percentage of shrub coverage had no impact on bear inhabitance. The best fitting model further predicted habitats in Bukkasagara, Agoli, and Benakal reserved forests to have 38%,75%, and 88%, respectively, of their sampled grid cells with high occupancies (.0.70) albeit little or no legal protection. We recommend a conservation strategy that includes protection of vegetation stand- structure, maintenance of soil moisture, and enrichment of habitat for the long-term welfare of this species. Key words: conservation, distribution, ecology, India, Karnataka, Melursus ursinus, occupancy modelling, sloth bears DOI: 10.2192/URSUS-D-14-00008.1 Ursus 25(2):111–120 (2014) Conservation and management policies and prac- et al. 2007, Krishna et al. 2008, Boyd and Foody tices directed at animal species should ideally be 2011, Nandy et al. 2012). However, occurrence or developed from complete information on demo- abundance of species might not be a veritable output graphic characteristics, behavioral patterns, life- of the relationship between a species and its habitat, history traits, and habitat use (Margules and Pressey because occurrence and abundance can be an 2000). Habitat use by a species, and the factors that imperfect surrogate for demographic performance influence habitat use, should in turn be evaluated (Van Horne 1983, Hobbs and Hanley 1990, Tyre using rigorous statistical and modelling techniques. et al. 2001). Therefore, patterns of occupancy along With recent advances in geo-spatial tools and with occupancy correlates can only determine modelling techniques, predicting species occurrence, habitat suitability and its capacity to support distribution, and abundance has become common populations. This functional link between a species’ (e.g., Scott et al. 2001, Pearce and Boyce 2006, Best occupancy and the environmental factors influencing it is critical for understanding habitat processes that 6email: [email protected] can be used to guide management (Franklin et al. 111 112 CONSERVATION OF SLOTH BEARS N Das et al. 2000, Breininger and Carter 2003). This exercise is of the species with respect to feeding, hiding, and even more important for generalist species that occur other requisites. This information is crucial to primarily outside protected areas and are involved in identify suitable habitats for conservation and conflicts with humans, including human casualties. development of management plans. Our objective The sloth bear (Melursus ursinus) in India serves as was to estimate occupancy of sloth bears and assess a model species under these criteria. Because of the potential effects of environmental and anthro- resource extraction, habitat fragmentation, habitat pogenic determinants such that we can establish loss, and high conflict across their range in drier potential suitability of habitats and demarcate them regions in central (Johnsingh 1986, Servheen 1990, for long-term conservation of the species. Chauhan et al. 1999, Rajpurohit and Krausman 2000, Bargali 2004), western, and southeastern (Krishna Raju et al. 1987) India, Garshelis et al. Study area (1999b:234–235, 2008) appealed for a concerted We conducted the study in 6 sites in the revenue action to ‘‘expand and update’’ distribution maps districts of Hospet and Koppal, specifically Daroji of the species in ‘‘relation to forest cover and Wildlife Sanctuary (WLS; 15u169N, 76u369E; 5,083 ha), boundaries of protected areas.’’ Such an action is Bukkasagara Reserve Forest (RF; 15u199N, 76u339E; imperative ‘‘to delineate discrete population units’’ 3,169 ha), Daroji RF (15u149N, 76u409E; 465 ha), coupled with information on ‘‘land use and land Toranagallu RF (15u129N, 76u419E; 547 ha), Agoli conditions’’ in regions outside the protected area RF (15u289N, 76u239E; 2,796 ha), and Benakal RF network to assess their potential for supporting (15u269N, 76u239E; 3,864 ha; Fig. 1). We selected these viable populations (Garshelis et al. 2008). areas based on their close proximity to each other The sloth bear is endemic to the Indian subcon- and unpublished reports of sloth bear presence and tinent (Erdbrink 1953, Sathyakumar et al. 2012), incidences of conflicts with humans. Only Daroji WLS with a historical distribution from the foothills of the and a non-demarcated 2,685.50 ha of Bukkasagara Himalayas in northern India to the dry slopes of the RF is ‘‘legally protected’’ for wildlife, whereas the Western Ghats in the south (Bargali et al. 2004). others are reserved forests located close to villages and However, sloth bear populations are currently are open to resource extraction, including timber limited to 5 regions in India: northern, northeastern, harvest, sand-mining, and livestock grazing (Kiran central, southeastern, and southwestern populations 2011). Daroji WLS is separated from Bukkasagara (Garshelis at al. 1999b, Johnsingh 2003, Yoganand RF by a road and village settlements along its et al. 2006, Sathyakumar et al. 2012). This drastic northern boundary but is contiguous with Daroji range contraction has rendered the species Vulner- RF and Toranagallu RF along its southeastern able to Extinction (IUCN 2013) and led to its border. Six kilometers northwest of Bukkasagara RF inclusion in Schedule I of the Indian Wildlife is Agoli RF and Benakal RF, which are divided by a (Protection) Act as amended in 2003 (GOI 1972, state highway. The habitat is largely rocky and 2003). Currently, only about 10% of the species’ bouldery; dry deciduous scrub and southern thorn current distribution in India contains high-quality forests (Champion and Seth 1968) are the only forest habitat (Yoganand et al. 2006). Techniques used to types, with Acacia spp. as the dominant species. The assess sloth bear–habitat relationships included as- vegetation in this region exists in a degraded state, sessment of home-range and habitat-selection analy- though afforestation programs have ensured promi- sis using radiotelemetry (Joshi et al. 1995, 1999; nent vegetation in certain pockets. The study area has a Ratnayeke et al. 2007), den-site examination, and semi-arid climate characterized by hot summers (34u– indirect bear signs such as droppings, tracks, and claw 45uC) during April–June and low rainfall (571.92 mm) marks (Akhtar et al. 2004, Chauhan et al. 2004). from June to November. These studies have thus revealed only qualitative habitat characteristics essential for the species. Sloth bears appear to use different habitats to Methods meet their life requisites (e.g., foraging, cover; Survey design Wrangham and Rubenstein 1986). Therefore, eco- We determined sampling units by overlaying the logical studies should characterize each habitat to study sites with 2-km2 grid cells as per the Forest develop a thorough understanding of requirements Department’s survey estimates of the existence of 1 Ursus 25(2):111–120 (2014) CONSERVATION OF SLOTH BEARS N Das et al. 113 Fig. 1. The location of the study sites, Daroji Wildlife Sanctuary, Bukkasagara Reserve Forest (RF), Daroji RF, Toranagallu RF, Agoli RF, and Benakal RF, and pictorial depiction of survey design for estimation of sloth bear occupancy are shown. Map showing (a) the location of study region in India, (b) the six study sites with their approximate geographical spacing overlaid with a 2-km2 grid, and (c) sampling units (strips) represented as ‘‘boxes’’ along the diagonals of each grid cell. The study was carried out in two phases, firstly during June– July 2011 and secondly, June–July 2012. bear/1.5 km2 in Daroji WLS (Kiran 2011). Diagonal and 30 grid cells, respectively (Fig. 1 and Table 1). of a square grid cell was designated as ‘‘1’’ if it ran Additionally, we selected grid cells with a minimum from the direction of north-west to the south-east spatial