Forced sympatry? Spatiotemporal interactions of ursids, the Himalayan brown bear and the Asiatic black bear, along a gradient of anthropic disturbances in Western Himalaya

Abstract

The coexistence of species with similar ecological niches implies that species must segregate along one or more niche axes in order to avoid competition. Partitioning of time, space, or resources is an essential niche dimension along which competitor species tend to coexist. The intensity of interspecific competition may vary under varying anthropogenic pressures, but such knowledge is scarce. We investigated the co‐occurrence patterns of two bear species, Asiatic Black Bear Ursus thibetanus and Himalayan Brown Bear Ursus arctos isabellinus, at two sites in the Western Himalayan region of India with similar ecological conditions and varying anthropogenic pressures. Camera trap datasets from the Great Himalayan National Park (GHNP) in Himachal Pradesh and the Bhagirathi basin in Uttarakhand were used to assess the species interactions. We used two species interaction models and kernel density estimates to understand the co‐occurrence pattern of the bear species and their interactions with humans. Our results provide insights into the spatiotemporal behavior of the two bear species and reveal their sympatric and allopatric relationships in two different anthropogenic environments. We found (1) a prominent association between the two bear species (98%) indicating spatial overlap in GHNP, but found spatial separation among the two species (93%) in Bhagirathi basin (2). In GHNP, the spatially co‐occurring bear species were found to be temporarily segregated, whereas in Bhagirathi, they showed spatial avoidance and similar activity patterns (3). In GHNP, human activities in the alpine habitat had a significant negative impact on brown bear presence. The comparative study revealed that the brown bear uses the forested habitats of GHNP due to high anthropogenic disturbances in the alpine areas, whereas no spatial association was observed in the Bhagirathi basin with comparatively low anthropogenic disturbances. The results highlight that, in addition to biological factors, anthropogenic pressures can also influence interspecific competition.