Differential Changes in Circulating Steroid Hormones in Hibernating Brown Bears: Preliminary Conclusions and Caveats

Frøbert, Anne Mette; Toews, Julia N C; Nielsen, Claus Gyrup; Brohus, Malene; Kindberg, Jonas; Jessen, Niels; Fröbert, Ole; Hammond, Geoffrey L.; Overgaard, Michael Toft

doi:10.1086/721154

Cited by 2 publications

(2 citation statements)

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“…In captive non-hibernating bears no data for cortisol seasonal patterns are available to our knowledge. On the contrary, in captive brown bears whose hibernation was induced, cortisol concentration was higher during hibernation compared to hyperphagic period [ 39 ] and during autumn (hyperphagic period) compared to preceding summer [ 40 ], as also reported for their wild hibernating conspecifics [ 38 , 45 ].…”

Section: Introductionmentioning

confidence: 82%

“…Actually, cortisol seasonal pattern was disrupted in wild bears when artificially fed year-round [ 38 ]. Higher glucocorticoids were even found during hibernation compared to the active period in wild bears (black bears [ 44 ], brown bears [ 45 ]) when increasing lipolysis is necessary to provide energy from fat during prolonged winter fasting [ 46 ].…”

Section: Introductionmentioning

confidence: 99%

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Hibernating or not hibernating? Brown bears’ response to a mismatch between environmental natural cues and captive management, and its welfare implications

Dori,

Anastasio,

Macchi

et al. 2024

PLoS ONE

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In wild brown bears, likely factors triggering hibernation response to harsh environmental conditions are temperature, photoperiod, and food resources availability. In fact, constantly fed captive brown bears are described as skipping hibernation being active all year-round. Is the hibernation response so flexible and subordinate to contingencies, or else is an adaptation that, if dismissed, may negatively impact on bear well-being? This study investigates the potential hibernation response in captive brown bears under unvaried management conditions using an integrative approach simultaneously analyzing multiple animal-based variables together with environmental covariates. Data from a mid-latitude zoo revealed distinct behavioral, fecal glucocorticoids, and body condition score seasonal fluctuations, resembling natural hibernation cycles, despite constant food access. Environmental variables like photoperiod and visitor numbers significantly influenced activity levels. Bears exhibited behaviors indicative of hyperphagia and fall transition, such as appetitive feeding and denning behaviors. Hormonal analyses revealed high fecal cortisol metabolites levels during hyperphagia, suggesting physiological responses to seasonal changes. Findings underscore the importance of environmental cues and food availability in shaping zoo bear behavior and physiology. Considering that the hibernating vs. non-hibernating description might represent an oversimplification, management strategies should deal with captive bear potential need to freely express their adaptive predispositions by accommodating their natural behaviors, such as providing denning spots and adjusting diet composition as soon as typical hyperphagic and predenning behaviors emerge, ultimately enhancing their well-being.

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