The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears
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...
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ftdatacite:10.25384/sage.c.4830888 2023-05-15T15:02:03+02:00 The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears Ware, Jasmine V. Rode, Karyn D. Robbins, Charles T. Leise, Tanya Weil, Colby R. Jansen, Heiko T. 2020 https://dx.doi.org/10.25384/sage.c.4830888 https://sage.figshare.com/collections/The_Clock_Keeps_Ticking_Circadian_Rhythms_of_Free-Ranging_Polar_Bears/4830888 unknown SAGE Journals https://dx.doi.org/10.1177/0748730419900877 CC BY 4.0 https://creativecommons.org/licenses/by/4.0 CC-BY 110306 Endocrinology FOS Clinical medicine 69999 Biological Sciences not elsewhere classified FOS Biological sciences Neuroscience Collection article 2020 ftdatacite https://doi.org/10.25384/sage.c.4830888 https://doi.org/10.1177/0748730419900877 2021-11-05T12:55:41Z 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. Article in Journal/Newspaper Arctic Chukchi Sea ice Ursus maritimus DataCite Metadata Store (German National Library of Science and Technology) Arctic |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
unknown |
topic |
110306 Endocrinology FOS Clinical medicine 69999 Biological Sciences not elsewhere classified FOS Biological sciences Neuroscience |
spellingShingle |
110306 Endocrinology FOS Clinical medicine 69999 Biological Sciences not elsewhere classified FOS Biological sciences Neuroscience Ware, Jasmine V. Rode, Karyn D. Robbins, Charles T. Leise, Tanya Weil, Colby R. Jansen, Heiko T. The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears |
topic_facet |
110306 Endocrinology FOS Clinical medicine 69999 Biological Sciences not elsewhere classified FOS Biological sciences Neuroscience |
description |
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. |
format |
Article in Journal/Newspaper |
author |
Ware, Jasmine V. Rode, Karyn D. Robbins, Charles T. Leise, Tanya Weil, Colby R. Jansen, Heiko T. |
author_facet |
Ware, Jasmine V. Rode, Karyn D. Robbins, Charles T. Leise, Tanya Weil, Colby R. Jansen, Heiko T. |
author_sort |
Ware, Jasmine V. |
title |
The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears |
title_short |
The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears |
title_full |
The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears |
title_fullStr |
The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears |
title_full_unstemmed |
The Clock Keeps Ticking: Circadian Rhythms of Free-Ranging Polar Bears |
title_sort |
clock keeps ticking: circadian rhythms of free-ranging polar bears |
publisher |
SAGE Journals |
publishDate |
2020 |
url |
https://dx.doi.org/10.25384/sage.c.4830888 https://sage.figshare.com/collections/The_Clock_Keeps_Ticking_Circadian_Rhythms_of_Free-Ranging_Polar_Bears/4830888 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Chukchi Sea ice Ursus maritimus |
genre_facet |
Arctic Chukchi Sea ice Ursus maritimus |
op_relation |
https://dx.doi.org/10.1177/0748730419900877 |
op_rights |
CC BY 4.0 https://creativecommons.org/licenses/by/4.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.25384/sage.c.4830888 https://doi.org/10.1177/0748730419900877 |
_version_ |
1766334054489128960 |