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Untangling the influence of ambient temperature & photoperiod surrounding hibernation activity in American black bears (Ursus americanus)

Holcombe, Brogan1

Published Apr 22, 2026 on Dryad. https://doi.org/10.5061/dryad.7pvmcvf6z

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Apr 22, 2026 version files 12.24 MB

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Abstract

Hibernation behavioral ecology remains understudied due to challenges in researching this cryptic physiological state. However, understanding relationships between physiological and environmental cues during hibernation is important for predicting behaviors in a changing climate. We examined behaviors of temporarily captive American black bears (Ursus americanus) exposed to natural environmental fluctuations surrounding hibernation. We analyzed 22,000+ hours of continuous video recordings of four female black bears, categorizing 45 behaviors. We used generalized linear mixed models and AIC model selection to analyze behaviors in relation to environmental (e.g., temperature, photoperiod) and physiological (e.g., body mass changes, hibernation stages) factors. We found a strongly supported interaction between photoperiod and temperature in 3 of 5 physiological stages in driving active behaviors, revealing potential drivers for hibernation onset and arousal. Photoperiod and temperature influenced activity levels, particularly during hyperphagia and den emergence, while temperature alone influenced activity during hibernation onset. Thus, predicted increases in temperatures due to climate change could lead to increased activity, especially surrounding hibernation onset. To our knowledge, no studies have investigated the interplay between photoperiod and temperature in bear hibernation ecology. We also highlight the potential for a mismatch between physiology and environmental cues in areas projected to experience increased temperatures under a changing climate.