Occupancy and Detection:
This study provides the first ever occupancy estimate for sloth bears from Nepal. Sloth bears were elusive species with less than a half (p= 0.44) probability of detection. Their signs were detected in 21 out of the sampled 45 grids, giving a naïve occupancy of 0.46. By explicitly incorporating the imperfect detection of animals into the occupancy estimate, the proportion of area occupied by sloth bear in Chitwan national park substantially increased (Ѱ = 0.53). An increase in habitat occupancy by 15% over the naïve estimate highlights the importance of considering the imperfect detection when studying sloth bears.
Our estimates are comparable to earlier studies on sloth bears outside Nepal (See Table 4). Habitat occupancy estimates for the sloth bear have varied between 0.54 to 0.83 in India. This difference might be because of difference in the home range of the species. The home range for sloth bears in Nepal is estimated at 9-14 sq.km in Chitwan (Joshi et al .1995) which is lower than in India estimated at 12 sq. km for a female and 85 sq. km for a male (Yoganand et al. 2005) and higher than that estimated for sub-species Melursus ursinus ornatus at 2.2 and 3.8 sq.km in Srilanka (Ratnayeke et al. 2007, 2021) respectively for female and male sloth bears. Additionally, most of the reported studies of sloth bear occupancy in India are from the Western ghats that has one of the largest blocks of contiguous forest cover and diversity of habitat conditions consisting of semi-evergreen, tropical moist, dry deciduous, thorny forest and scrub interspersed with agricultural area and rocky outcrops while our study area is relatively homogenous with small grasslands patches interspersed in a deciduous forest habitat. The occupancy-abundance relationship of species tends to be linked (Gaston et al. 2002; Zukerberg et al. 2008) particularly at the small and homogenous areas (Hui et al. 2009). Considering our occupancy estimate of 0.53 obtained from our sampling of the study area, the suitable habitat inside the park is ~500 sq.km and the population around ~100-150 individuals. It indicates that sloth bears have fairly wide distribution throughout the park, with relatively higher occupancy (psi >0.53) areas along the northern boundary of the park (Figure 5) . Both Laurie & Seidensticker (1977) and Garshelis et al (1999) recognize that there is uneven distribution of sloth bears with high density in the alluvial floodplains along the bank of Rapti river in north part of the park and relatively lower density on rest of the park dominated by upland Sal forest.