Seal body condition and atmospheric circulation patterns influence polar bear body condition, recruitment, and feeding ecology in the Chukchi Sea

Polar bears (Ursus maritimus) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial–te...

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Bibliographic Details
Published in:Global change biology 2021-06, Vol.27 (12), p.2684-2701
Main Authors: Rode, Karyn D., Regehr, Eric V., Bromaghin, Jeffrey F., Wilson, Ryan R., St. Martin, Michelle, Crawford, Justin A., Quakenbush, Lori T.
Format: Article
Language:English
Subjects:
Ablation
Animal behavior
Aquatic mammals
Arctic Oscillation
Atmospheric circulation
bearded seal
Body condition
Diet
Ecological effects
Environmental changes
Erignathus barbatus
Feeding
Females
Habitats
Hunting
Ice conditions
Ice cover
Mammals
Marine ecosystems
Marine mammals
Ocean temperature
Polar bears
Polar environments
Populations
Prey
Probability theory
Pusa hispida
QFASA
Recruitment
Recruitment (fisheries)
ringed seal
Satellite observation
Sea ice
Seals
Seals (animals)
Subpopulations
Temporal variations
Ursus maritimus
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Summary:Polar bears (Ursus maritimus) are experiencing loss of sea ice habitats used to access their marine mammal prey. Simultaneously, ocean warming is changing ecosystems that support marine mammal populations. The interactive effects of sea ice and prey are not well understood yet may explain spatial–temporal variation in the response of polar bears to sea ice loss. Here, we examined the potential combined effects of sea ice, seal body condition, and atmospheric circulation patterns on the body condition, recruitment, diet, and feeding probability of 469 polar bears captured in the Chukchi Sea, 2008–2017. The body condition of ringed seals (Pusa hispida), the primary prey of females and subadults, was related to dietary proportions of ringed seal, feeding probability, and the body condition of females and cubs. In contrast, adult males consumed more bearded seals (Erignathus barbatus) and exhibited better condition when bearded seal body condition was higher. The litter size, number of yearlings per adult female, and the condition of dependent young were higher following winters characterized by low Arctic Oscillation conditions, consistent with a growing number of studies. Body condition, recruitment, and feeding probability were either not associated or negatively associated with sea ice conditions, suggesting that, unlike some subpopulations, Chukchi Sea bears are not currently limited by sea ice availability. However, spring sea ice cover declined 2% per year during our study reaching levels not previously observed in the satellite record and resulting in the loss of polar bear hunting and seal pupping habitat. Our study suggests that the status of ice seal populations is likely an important factor that can either compound or mitigate the response of polar bears to sea ice loss over the short term. In the long term, neither polar bears nor their prey are likely robust to limitless loss of their sea ice habitat. Body condition, feeding, and recruitment of Chukchi Sea polar bears during 2008–2017 were influenced by sea ice conditions, ice seal body condition, and a climatic index. Spring feeding probability and body condition of females and dependent young were higher following years with higher ringed seal body condition. Adult males consumed more bearded seals and exhibited better condition when bearded seal body condition (blue) was higher. Recruitment was higher following winters with low winter Arctic Oscillations (green). Interactions among seal popula
ISSN:1354-1013
1365-2486
DOI:10.1111/gcb.15572