Phenotypic plasticity and climate change: Can polar bears respond to longer Arctic summers with an adaptive fast?

摘要: Plasticity in the physiological and behavioural responses of animals to prolonged food shortages may determine persistence species under climate warming. This is particularly applicable for that can “adaptively fast” by conserving protein protect organ function while catabolizing endogenous tissues. Some Ursids, including polar bears (Ursus maritimus), adaptively fast during winter hibernation—and it has been suggested also employ this strategy summer. We captured 57 adult female Southern Beaufort Sea (SBS) summer 2008 2009 measured blood variables indicate feeding, regular fasting, adaptive fasting. assessed tissue δ13C δ15N infer diet, body condition via mass length. found on shore maintained lipid stores scavenging bowhead whale (Balaena mysticetus) carcasses from human harvest, those followed retreating sea ice beyond continental shelf were deprived. They had low ratios urea creatinine (U:C), normally associated with However, they exhibited albumin glucose (indicative loss) elevated alanine aminotransferase ghrelin (which fall fasting). Thus, the ~ 70% SBS subpopulation spends experiences more a regular, rather than adaptive, fast. will lengthen as declines. The resulting loss prior could be mechanism driving reported correlation between bear reproduction survival SBS.