Dynamic partitioning across space, time and diet promotes coexistence of sympatric large omnivores

Understanding coexistence mechanisms among sympatric large carnivores is critical for their conservation, particularly in human-modified mountain landscapes where ecological information remains limited. We investigated the spatiotemporal and dietary dynamics between the Asiatic black bear ( Ursus thibetanus ) and the Himalayan brown bear ( Ursus arctos isabellinus ) in the anthropogenically influenced landscape of Dhauladhar Wildlife sanctuary situated in the Greater Himalayas. Using two years of camera-trap data (2023-2024) combined with scat analysis, we examined seasonal patterns of habitat use, activity rhythms, food habits, and responses to human settlements within a multidimensional niche framework. We found that spatial overlap between the species varied seasonally, being lowest in spring, moderate in summer, highest in autumn, and absent in pre-winter or peak hyperphagia, while temporal overlap showed an inverse pattern indicating fine-scale temporal segregation as a mechanism to minimize direct encounters. Proximity to human settlements influenced activity patterns of Asiatic black bears, which exhibited increased nocturnality near disturbed areas, whereas Himalayan brown bears maintained relatively stable activity patterns and primarily occupied alpine and subalpine habitats away from human influence. Dietary analyses revealed predominantly plant-based diets for both the species, with pronounced seasonal shifts driven by resource phenology. Dietary overlap also varied seasonally, with clear segregation in spring and increasing overlap from summer to pre-winter. We demonstrated that the coexistence between these sympatric bears is maintained through seasonally dynamic partitioning across spatial, temporal, and trophic niche dimensions. The simultaneous integration of these niche axes within a single multidimensional space emphasizes the benefit of moving away from single-axis approaches in community ecology, and provides an empirical test of the partitioning of coexistence by large sympatric omnivores dynamically across seasons in a human-modified landscape. The sanctuary supports a largely intact natural foraging system, highlighting the importance of maintaining habitat heterogeneity and minimizing human disturbance for long-term bear conservation.