44.3 Saturday, Jan. 5 Phenology of hibernation and reproduction in free-living arctic ground squirrels WILLIAMS, CT*; SHERIFF, MJ; BARNES, BM; BUCK, CL; University of Alaska Anchorage; University of Alaska Fairbanks; University of Alaska Fairbanks; University of Alaska Anchorage firstname.lastname@example.org
Climate warming is predicted to lengthen the growing season, particularly at high latitudes, which provides increased foraging opportunities, although biological interactions can also be disrupted due to intra- and inter-specific variability in the response to climate forcing. We developed a method of using patterns of core body temperature in free-living arctic ground squirrels to precisely determine the timing of key seasonal events including hibernation, mating and parturition, and immergence and emergence from the hibernacula. Long-term data collected from two arctic ground squirrel populations living 20 km apart in northern Alaska indicate that individuals respond plastically to environmental conditions with earlier reproduction at the site characterized by earlier snow melt. The timing of parturition was tightly linked to the termination of heterothermy and subsequent emergence from the hibernacula at both sites, whereas timing of entrance into hibernation was only weakly correlated with date of parturition. Females ended heterothermy in spring coincident with rising soil temperatures from winter minima, but since average soil temperatures did not differ between the two sites, a single threshold in warming cannot explain the differences in timing of spring emergence and reproduction between the two populations.