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Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea

BACKGROUND: Polar bears (Ursus maritimus) of the Beaufort Sea enter hyperphagia in spring and gain fat reserves to survive periods of low prey availability. We collected information on seals killed by polar bears (n = 650) and hunting attempts on ringed seal (Pusa hispida) lairs (n = 1396) observed...

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Autores principales: Pilfold, Nicholas W., Derocher, Andrew E., Stirling, Ian, Richardson, Evan, Andriashek, Dennis
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3400654/
https://www.ncbi.nlm.nih.gov/pubmed/22829949
http://dx.doi.org/10.1371/journal.pone.0041429
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author Pilfold, Nicholas W.
Derocher, Andrew E.
Stirling, Ian
Richardson, Evan
Andriashek, Dennis
author_facet Pilfold, Nicholas W.
Derocher, Andrew E.
Stirling, Ian
Richardson, Evan
Andriashek, Dennis
author_sort Pilfold, Nicholas W.
collection PubMed
description BACKGROUND: Polar bears (Ursus maritimus) of the Beaufort Sea enter hyperphagia in spring and gain fat reserves to survive periods of low prey availability. We collected information on seals killed by polar bears (n = 650) and hunting attempts on ringed seal (Pusa hispida) lairs (n = 1396) observed from a helicopter during polar bear mark-recapture studies in the eastern Beaufort Sea in spring in 1985–2011. We investigated how temporal shifts in ringed seal reproduction affect kill composition and the intraspecific vulnerabilities of ringed seals to polar bear predation. PRINCIPAL FINDINGS: Polar bears primarily preyed on ringed seals (90.2%) while bearded seals (Erignathus barbatus) only comprised 9.8% of the kills, but 33% of the biomass. Adults comprised 43.6% (150/344) of the ringed seals killed, while their pups comprised 38.4% (132/344). Juvenile ringed seals were killed at the lowest proportion, comprising 18.0% (62/344) of the ringed seal kills. The proportion of ringed seal pups was highest between 2007–2011, in association with high ringed seal productivity. Half of the adult ringed seal kills were ≥21 years (60/121), and kill rates of adults increased following the peak of parturition. Determination of sex from DNA revealed that polar bears killed adult male and adult female ringed seals equally (0.50, n = 78). The number of hunting attempts at ringed seal subnivean lair sites was positively correlated with the number of pup kills (r(2) = 0.30, P = 0.04), but was not correlated with the number of adult kills (P = 0.37). CONCLUSIONS/SIGNIFICANCE: Results are consistent with decadal trends in ringed seal productivity, with low numbers of pups killed by polar bears in spring in years of low pup productivity, and conversely when pup productivity was high. Vulnerability of adult ringed seals to predation increased in relation to reproductive activities and age, but not gender.
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spelling pubmed-34006542012-07-24 Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea Pilfold, Nicholas W. Derocher, Andrew E. Stirling, Ian Richardson, Evan Andriashek, Dennis PLoS One Research Article BACKGROUND: Polar bears (Ursus maritimus) of the Beaufort Sea enter hyperphagia in spring and gain fat reserves to survive periods of low prey availability. We collected information on seals killed by polar bears (n = 650) and hunting attempts on ringed seal (Pusa hispida) lairs (n = 1396) observed from a helicopter during polar bear mark-recapture studies in the eastern Beaufort Sea in spring in 1985–2011. We investigated how temporal shifts in ringed seal reproduction affect kill composition and the intraspecific vulnerabilities of ringed seals to polar bear predation. PRINCIPAL FINDINGS: Polar bears primarily preyed on ringed seals (90.2%) while bearded seals (Erignathus barbatus) only comprised 9.8% of the kills, but 33% of the biomass. Adults comprised 43.6% (150/344) of the ringed seals killed, while their pups comprised 38.4% (132/344). Juvenile ringed seals were killed at the lowest proportion, comprising 18.0% (62/344) of the ringed seal kills. The proportion of ringed seal pups was highest between 2007–2011, in association with high ringed seal productivity. Half of the adult ringed seal kills were ≥21 years (60/121), and kill rates of adults increased following the peak of parturition. Determination of sex from DNA revealed that polar bears killed adult male and adult female ringed seals equally (0.50, n = 78). The number of hunting attempts at ringed seal subnivean lair sites was positively correlated with the number of pup kills (r(2) = 0.30, P = 0.04), but was not correlated with the number of adult kills (P = 0.37). CONCLUSIONS/SIGNIFICANCE: Results are consistent with decadal trends in ringed seal productivity, with low numbers of pups killed by polar bears in spring in years of low pup productivity, and conversely when pup productivity was high. Vulnerability of adult ringed seals to predation increased in relation to reproductive activities and age, but not gender. Public Library of Science 2012-07-19 /pmc/articles/PMC3400654/ /pubmed/22829949 http://dx.doi.org/10.1371/journal.pone.0041429 Text en Pilfold et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Pilfold, Nicholas W.
Derocher, Andrew E.
Stirling, Ian
Richardson, Evan
Andriashek, Dennis
Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea
title Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea
title_full Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea
title_fullStr Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea
title_full_unstemmed Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea
title_short Age and Sex Composition of Seals Killed by Polar Bears in the Eastern Beaufort Sea
title_sort age and sex composition of seals killed by polar bears in the eastern beaufort sea
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3400654/
https://www.ncbi.nlm.nih.gov/pubmed/22829949
http://dx.doi.org/10.1371/journal.pone.0041429
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