In the Arctic summer, extent and duration of sea ice melt is increasing, displacing Alaskan polar bears from ice in productive near-shore waters to deep-water ice or to land. In these habitats, seal prey is likely at low availability. Additionally, extensive open water may increase long-distance swimming. It is unknown how these changes affect metabolic rates and thermoregulation of polar bears. We recorded body temperature (Tb) with loggers implanted adjacent to the abdominal peritoneum, ventral to the linea alba, in 4 bears on deep-water ice (May–Oct) and 5 bears on shore (Aug–Oct) in the Beaufort Sea.
Results/Conclusions
Tb of ice bears declined from a weekly mean of 37.2–37.5°C (May 23–Jun 03) to 34.7–36.6°C (Sep 21–Oct 09). We propose this reflects a gradual reduction in metabolic rate in response to limited seal availability. Bears had unexpected, rapid bouts of Tb decline and recovery. In Aug–Oct, ice bears averaged 0.65 bouts per day (95% were ≤ 12 hours) that reached a mean minimum Tb of 33.6°C; shore bears averaged 1.06 bouts per day (94% were ≤ 12 hours) that reached a mean minimum Tb of 28.6°C. The cause of these bouts and why they were more frequent and reached a lower Tb for bears on shore is not clear. Pending analyses explore relationships between gradual Tb decline and energetics; relationships between bouts of low Tb and swimming behavior; and implications of these patterns for polar bears in the changing Arctic summer.