Dietary Ecology of Alaskan Polar Bears (Ursus Maritimus) Through Time and in Response to Arctic Climate Change
Sponsor
National Science Foundation, NSF-PAR ID: 10450850
Published In
Global Change Biology
Document Type
Article
Publication Date
4-1-2021
Subjects
Polar bears, Climatic changes
Abstract
Arctic climate change poses serious threats to polar bears (Ursus maritimus) as reduced sea ice makes seal prey inaccessible and marine ecosystems undergo bottom-up reorganization. Polar bears' elongated skulls and reduced molar dentition, as compared to their sister species the grizzly bear (Ursus arctos), are adaptations associated with hunting seals on sea ice and a soft, lipid-rich diet of blubber and meat. With significant declines in sea ice, it is unclear if and how polar bears may be altering their diets. Clarifying polar bear dietary responses to changing climates, both today and in the past, is critical to proper conservation and management of this apex predator. This is particularly important when a dietary strategy may be maladaptive. Here, we test the hypothesis that hard-food consumption (i.e., less preferred foods including bone), inferred from dental microwear texture analysis, increased with Arctic warming. We find that polar bears demonstrate a conserved absence of hard-object feeding in Alaska through time (including approximately 1000 years ago), until the 21st century, consistent with a highly conserved and specialized diet of soft blubber and flesh. Notably, our results also suggest that some 21st-century polar bears may be consuming harder foods (e.g., increased carcass utilization, terrestrial foods including garbage), despite having skulls and metabolisms poorly suited for such a diet. Prior to the 21st century, only polar bears with larger mandibles demonstrated increased hard-object feeding, though to a much lower degree than closely related grizzly bears which regularly consume mechanically challenging foods. Polar bears, being morphologically specialized, have biomechanical constraints which may limit their ability to consume mechanically challenging diets, with dietary shifts occurring only under the most extreme scenarios. Collectively, the highly specialized diets and cranial morphology of polar bears may severely limit their ability to adapt to a warming Arctic.
Rights
National Science Foundation, Grant/Award Number 10450850.
The Federal awarding agency reserves a royalty-free, nonexclusive and irrevocable right to reproduce, publish, or otherwise use the work for Federal purposes, and to authorize others to do so.
This is the author's accepted manuscript version. The final version can be found on the publisher's website: https://doi.org/10.1111/gcb.15573
DOI
10.1111/gcb.15573
Persistent Identifier
https://archives.pdx.edu/ds/psu/35164
Citation Details
Petherick, A. S., Reuther, J. D., Shirar, S. J., Anderson, S. L., & DeSantis, L. R. G. (2021). [Post-print]. Dietary ecology of Alaskan polar bears ( Ursus maritimus ) through time and in response to Arctic climate change. Global Change Biology, gcb.15573. https://doi.org/10.1111/gcb.15573
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Supplementary Material