Journal article
Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment
American journal of physiology. Regulatory, integrative and comparative physiology, Vol.303(9), pp.R890-R902
11/01/2012
Handle:
https://hdl.handle.net/2376/103970
PMID: 22972838
Abstract
Seasonal cycles of reproduction, migration, and hibernation are often synchronized to changes in daylength (photoperiod). Ecological and evolutionary pressures have resulted in physiological specializations enabling animals to occupy a particular temporal niche within the diel cycle leading to characteristic activity patterns. In this study, we characterized the annual locomotor activity of captive brown bears (Ursus arctos). Locomotor activity was observed in 18 bears of varying ages and sexes during the active (Mar-Oct) and hibernating (Nov-Feb) seasons. All bears exhibited either crepuscular or diurnal activity patterns. Estimates of activity duration (α) and synchronization to the daily light:dark cycle (phase angles) indirectly measured photoresponsiveness. α increased as daylength increased but diverged near the autumnal equinox. Phase angles varied widely between active and hibernating seasons and exhibited a clear annual rhythm. To directly test the role of photoperiod, bears were exposed to controlled photoperiod alterations. Bears failed to alter their daily activity patterns (entrain) to experimental photoperiods during the active season. In contrast, photic entrainment was evident during hibernation when the daily photocycle was shifted and when bears were exposed to a skeleton (11:1:11:1) photoperiod. To test whether entrainment to nonphotic cues superseded photic entrainment during the active season, bears were exposed to a reversed feeding regimen (dark-fed) under a natural photocycle. Activity shifted entirely to a nocturnal pattern. Thus daily activity in brown bears is highly modifiable by photoperiod and food availability in a stereotypic seasonal fashion.
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Details
- Title
- Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment
- Creators
- Jasmine V Ware - Departments of Veterinary Comparative Anatomy, Pharmacology, and PhysiologyO. Lynne Nelson - Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, Washington; andCharles T Robbins - School of the Environment, School of Biological Sciences, Washington State University, Pullman, WashingtonHeiko T Jansen - Departments of Veterinary Comparative Anatomy, Pharmacology, and Physiology
- Publication Details
- American journal of physiology. Regulatory, integrative and comparative physiology, Vol.303(9), pp.R890-R902
- Academic Unit
- Integrative Physiology and Neuroscience, Department of; Environment, School of the (CAHNRS)
- Identifiers
- 99900547062801842
- Language
- English
- Resource Type
- Journal article