| Summary: | 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 (T b ) 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. T b 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). Bears had unexpected, rapid bouts of T b decline and recovery. In Aug–Oct, ice bears averaged 0.65 bouts per day (95% were 蠄 12 hours) that reached a mean minimum T b of 33.6°C; shore bears averaged 1.06 bouts per day (94% were 蠄 12 hours) that reached a mean minimum T b of 28.6°C. The cause of these bouts and why they were more frequent and reached a lower T b for bears on shore is not clear. Pending analyses contrast T b to data collected from loggers implanted in the rump; relationships between bouts of low T b and swimming behavior; and implications of these patterns for polar bears in the changing Arctic summer. Grant Funding Source : National Science Foundation 0732713
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