The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears
| العنوان: | The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears |
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| المؤلفون: | Tanya L. Leise, Charles T. Robbins, Jasmine V. Ware, Karyn D. Rode, Heiko T. Jansen, Colby R. Weil |
| المصدر: | Journal of Biological Rhythms. 35:180-194 |
| بيانات النشر: | SAGE Publications, 2020. |
| سنة النشر: | 2020 |
| مصطلحات موضوعية: | 0106 biological sciences, 0301 basic medicine, Physiology, Ursus maritimus, Photoperiod, 010603 evolutionary biology, 01 natural sciences, 03 medical and health sciences, Circadian Clocks, Physiology (medical), biology.animal, Sea ice, Animals, Photic zone, Circadian rhythm, Ecosystem, geography, geography.geographical_feature_category, Behavior, Animal, Free ranging, biology, Arctic Regions, Reproduction, Circadian Rhythm, The arctic, 030104 developmental biology, Oceanography, Arctic, Geographic Information Systems, Environmental science, Polar, Female, Seasons, Ursidae |
| الوصف: | Life in the Arctic presents organisms with multiple challenges, including extreme photic conditions, cold temperatures, and annual loss and daily movement of sea ice. Polar bears ( Ursus maritimus) evolved under these unique conditions, where they rely on ice to hunt their main prey, seals. However, very little is known about the dynamics of their daily and seasonal activity patterns. For many organisms, activity is synchronized (entrained) to the earth’s day/night cycle, in part via an endogenous (circadian) timekeeping mechanism. The present study used collar-mounted accelerometer and global positioning system data from 122 female polar bears in the Chukchi and Southern Beaufort Seas collected over an 8-year period to characterize activity patterns over the calendar year and to determine if circadian rhythms are expressed under the constant conditions found in the Arctic. We reveal that the majority of polar bears (80%) exhibited rhythmic activity for the duration of their recordings. Collectively within the rhythmic bear cohort, circadian rhythms were detected during periods of constant daylight (June-August; 24.40 ± 1.39 h, mean ± SD) and constant darkness (23.89 ± 1.72 h). Exclusive of denning periods (November-April), the time of peak activity remained relatively stable (acrophases: ~1200-1400 h) for most of the year, suggesting either entrainment or masking. However, activity patterns shifted during the spring feeding and seal pupping season, as evidenced by an acrophase inversion to ~2400 h in April, followed by highly variable timing of activity across bears in May. Intriguingly, despite the dynamic environmental photoperiodic conditions, unpredictable daily timing of prey availability, and high between-animal variability, the average duration of activity (alpha) remained stable (11.2 ± 2.9 h) for most of the year. Together, these results reveal a high degree of behavioral plasticity in polar bears while also retaining circadian rhythmicity. Whether this degree of plasticity will benefit polar bears faced with a loss of sea ice remains to be determined. |
| تدمد: | 1552-4531 0748-7304 |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::3adbe884e6d31e8aced524885938c644 https://doi.org/10.1177/0748730419900877 |
| حقوق: | OPEN |
| رقم الأكسشن: | edsair.doi.dedup.....3adbe884e6d31e8aced524885938c644 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 15524531 07487304 |
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