[PDF] A REVIEW OF BEAR EVOLUTION

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Noninvasive genetic assessment of sloth bear diversity and population structure in Nepal (Open Access)

Rajan Prasad Paudel,  Michito Shimozuru,  Rabin Kadariya,  Naresh Subedi,  Toshio Tsubota

Ursus 2026 (37e1), 1-16, (14 January 2026). https://doi.org/10.2192/URSUS-D-24-00024

KEYWORDS: genetic diversity, Melursus ursinus, Nepal, noninvasive DNA sampling, population genetics, population structure, sloth bear, wildlife conservation

The genetic diversity of wildlife populations is crucial in maintaining their fitness and resilience to environmental changes and disease. Despite their rarity, ecological importance, and being an endangered species of public concern, information on sloth bears (Melursus ursinus) from Nepal is limited, and they are yet to receive conservation priority. To address this gap, we conducted Nepal’s first noninvasive genetic surveys of sloth bear populations from 3 different habitat patches across their distribution range along the Churia-Terai landscape in Nepal between 2019 and 2021. Our study involved genotyping 127 samples using 12 microsatellite loci to determine the levels of genetic diversity and population genetic structure and using the control region of the mitochondrial genome for the haplotype analysis. We found 37 individuals in an area of approximately 1,000 km2 comprising forest and grassland habitats. Our results indicate that the sloth bears in Nepal are characterized by low genetic diversity (HE = 0.48) compared with other bear populations across its range. We had a limited number of individuals from different sampling areas, but their genotypes were consistent with there being no genetic structure between sampling areas. The study provides the crucial baseline information on the conservation genetics of sloth bears from Nepal and highlights the prospects for using noninvasive DNA sampling for research, monitoring, and conservation of bears.

Edible ant availability and distribution as resources for the Asiatic black bear (Open Access)

Kazuteru Mikuni,  Tomoki Mori,  Yasuaki Niizuma

Ursus 2026 (37e2), 1-11, (30 January 2026) https://doi.org/10.2192/URSUS-D-25-00001

KEYWORDS: Asiatic black bear, dietary habit, food availability, food distribution, Formicidae, Japan, myrmecophagy, Ursus thibetanus

The Asiatic black bear (Ursus thibetanus) is a generalist omnivore consuming a wide range of food items, including ants (family Formicidae) and other social insects during summer. The distribution of ant resources is thought to influence habitat selection by Asiatic black bear. We investigated the distribution of ant resources during summer in bear habitat in Shirakawa Village, Gifu Prefecture, Japan, which is approximately 96% forested. Our aims were to (1) identify general trends in the distribution of ant resources used by bears, (2) determine which ant species contribute to the overall availability of ant resources, (3) investigate the relationships between the availability of ant resources used by bears and environmental factors, and (4) discuss the relationship between the distribution of ant resources and summer habitat selection by bears based on existing research. Our findings suggest that environments with high percentage of loose stone coverage are likely to have high availability of ants used by Asiatic black bear. In particular, we observed a positive relation between the availability of Camponotus ants and canopy openness. Similarly, the availability of Lasius and Myrmica ants were positively related to loose stone coverage. Habitats characterized by high percentage of canopy openness or high loose stone coverage were mostly grassland, forest edge, and riparian areas, and likely to have high availability of ants. This trend is consistent with the distribution of other foods eaten by Asiatic black bears during summer. We suggest, therefore, that grassland, forest edges, and riparian areas are environments with abundant resources for ants because these environments provide high availability of resources for both ants and other bear foods in summer.