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Drivers of Arctic female grizzly movement-related habitat use from den emergence to green-up
Mark A. Edwards, Kerri E. Krawchuk, Evelyn H. Merrill, Andrew E. Derocher
Ursus 2025 (36e10), 1-15, (14 August 2025) https://doi.org/10.2192/URSUS-D-24-00016.R1
KEYWORDS: grizzly bear, habitat selection, mortality risk, movement ecology, reproductive status, resource availability, security cover, step-selection function, Ursus arctos
Arctic female grizzly bears (Ursus arctos) with cubs face a challenging period following den emergence to find quality resources when risk of infanticide is high and food is scarce. We used global positioning system (GPS) telemetry data grouped by reproductive state (solitary, females with cubs <1 yr old, females with cubs ≥1 yr old) to examine trade-offs between access to security cover and access to food during the hypophagic period from 5 June to 4 August (2003–2006), in the Mackenzie Delta region, Northwest Territories, in the Canadian Arctic. We used step-selection functions to model habitat selection with parameters for land cover, land cover diversity, and topography measured along the step and at the end. We fit the models for each individual and used 2-stage model-averaging to determine the top model for describing landscape factors influencing movement. We found that while female movement rates (i.e., step length = m/4-hr location interval) differed with reproductive state, movement-related habitat selection was similar. Females with cubs <1 year old moved the least (x̄ step length = 700 m, 95% CI [655–745]) compared with females with cubs ≥1 year old (x̄ = 1,484 m [1,415–1,553], P < 0.001), and females without cubs (x̄ = 1,652 m [1,581–1,723], P < 0.001), who moved the most. Across all reproductive states, our results suggest that females prioritize security over food availability along movement paths. Our results contribute to a better understanding of the behavioral decisions made by female grizzly bears and provide insights into trade-offs between security and food resources, when resource availability is uncertain.
Sloth bear denning behavior in eastern Karnataka, India (Open Access Article)
Shanmugavelu Swaminathan, Yogaraj Pannerselvam, Reagan Puspanathan, Thomas R. Sharp, Attur S. Arun, Kartick Satyanarayan, Geeta Seshamani
Ursus 2025 (36e11), 1-10, (3 October 2025) https://doi.org/10.2192/URSUS-D-24-00015R1
KEYWORDS: behavior, breeding, Deccan Plateau, denning, eastern Karnataka, India, Melursus ursinus, sloth bear
Eastern Karnataka, India, has abundant sloth bear (Melursus ursinus) habitat made up of rocky scrub jungle and an abundance of naturally occurring caves, which the bears use for resting (day) and natal or neonatal dens. We deployed cameras on active dens from 2014 to 2018 and collected sloth bear resting and maternal denning behavior. We estimated a total of 37 different families with cubs aged 4 months to 2 years over the study, 15 with 1 cub, 19 with 2 cubs, and 3 with 3 cubs, for an average of 1.68 cubs/family. Data were analyzed from 34 dens being used by single bears and 21 dens being used by families. No significant differences were found between the temporal activity patterns of families and single bears entering (P = 0.145) or exiting (P = 0.649) dens. Nor were there any significant differences between the two groups seasonally. However, families entered dens significantly earlier during summer than they did during winter (P = 0.006), likely to escape the heat and earlier human activity. Individual resting and maternal dens were used sporadically. Resting dens were used for 1 (84.1%), 2 (11.6%), or >2 consecutive days (4.3%) before the bear left. Maternal dens were used for 1 (81.4%), 2 (3.9%), or >2 days (14.7%). Families with young cubs (3–9 months old) used dens for more consecutive days than did single bears or families with independently walking cubs. In 2 male cub family break-up events, the mother left the den that the two bears had been inhabiting together, and the young male continued to use the den. Notable interactions between bears at den sites were documented as were other species observed denning with or near sloth bears.