Print PagePrevious research indicates that polar bears can reduce energetic expenditures (by reducing metabolic rate and activity levels) and efficiently utilize stored energy reserves. These abilities could provide critical means for surviving periods of limited access to their preferred prey, seals. During summer in the southern Beaufort Sea, some bears follow the retreating sea ice north while others remain land-bound. As a result of climate change, ice retreat is extended, forcing bears to remain on shore longer and carrying ice-bound bears into areas where seal density may be low. Both groups of bears face periods of potential food deprivation; we are investigating how they adjust energy uses and body reserves to cope with these new conditions, and ultimately, how climate change will affect population dynamics. In 2008 and 2009, 38 adult polar bears were captured in early summer. Tissue samples were collected and each individual was implanted with a body temperature (Tb) logger and fitted with a radio transmitter; 18 bears were recaptured in late summer, re-sampled and instruments recovered.
Results/Conclusions
Preliminary analyses of δ13C of exhaled CO2, respiratory exchange ratios (RERs), serum urea:creatinine ratios, and Tb suggest that ice-bound bears exhibit slightly reduced metabolic rates and may exhaust their lipid stores during fasting. Bears on shore had variable Tb and appear not to exhaust lipid stores. Pending analyses of activity levels, δ13C of fat tissue, δ15N of muscle tissue, muscle morphology, serum non-esterified fatty acids, and other blood parameters will clarify the benefits and drawbacks of remaining on shore and following the sea ice north in the context of changing summer conditions. Principal funding from US National Science Foundation (0732713).
