Fine-scale ecological and anthropogenic variables predict the habitat use and detectability of sloth bears in the Churia habitat of east Nepal

Once widespread throughout the tropical forests of the Indian Subcontinent, the sloth bears have suffered a rapid range collapse and local extirpations in the recent decades. A significant portion of their current distribution range is situated outside of the protected areas (PAs). These unprotected sloth bear populations are under tremendous human pressures, but little is known about the patterns and determinants of their occurrence in most of these regions. The situation is more prevalent in Nepal where virtually no systematic information is available for sloth bears living outside of the PAs. We undertook a spatially replicated sign survey-based single-season occupancy study intending to overcome this information gap for the sloth bear populations residing in the Trijuga forest of southeast Nepal. Sloth bear sign detection histories and field-based covariates data were collected between 2 October and 3 December 2020 at the 74 randomly chosen 4-km(2) grid cells. From our results, the model-averaged site use probability (psi +/- SE) was estimated to be 0.432 +/- 0.039, which is a 13% increase from the naive estimate (0.297) not accounting for imperfect detections of sloth bear signs. The presence of termite mound and the distance to the nearest water source were the most important variables affecting the habitat use probability of sloth bears. The average site-level detectability (p +/- SE) of sloth bear signs was estimated to be 0.195 +/- 0.003 and was significantly determined by the index of human disturbances. We recommend considering the importance of fine-scale ecological and anthropogenic factors in predicting the sloth bear-habitat relationships across their range in the Churia habitat of Nepal, and more specifically in the unprotected areas.

Automated summary

Sloth bears, once widespread in the tropical forests of the Indian Subcontinent, have seen a rapid decline in range and local extinctions. A significant portion of their current distribution is outside of protected areas and faces significant human pressures. This study focuses on the sloth bear populations residing in the Trijuga forest of southeast Nepal and aims to provide information about their occurrence patterns and determinants. The results suggest that the presence of termite mounds and the distance to the nearest water source are important factors affecting sloth bear habitat use probability. The study highlights the need to consider fine-scale ecological and anthropogenic factors in predicting sloth bear-habitat relationships.