Meeting Abstract
91.3 Wednesday, Jan. 7 Resource-dependent cold climate heterothermy in free-ranging red squirrels WOODS, S.B.*; BARNES, B.M.; HUMPHRIES, M.M.; Natural Resource Sciences, McGill University; Institute of Arctic Biology , University of Alaska Fairbanks; Natural Resource Sciences, McGill University murray.humphries@mcgill.ca
Although not as dramatic as daily or prolonged torpor expression, shallow reductions in body temperature (Tb) expressed by so-called homeothermic endotherms may be a significant contributor to their energy conservation during daily or seasonal periods of energy shortage. We documented Tb variation of a cold climate population of free-ranging red squirrels (Tamiasciurus hudsonicus) during winter using surgically implanted data loggers. Among the 24 individuals successfully monitored, minimum, average and maximum recorded Tb was 34.1, 38.1, and 42.3 oC, respectively. Tb was higher during activity than when in the nest and during the day than at night, with an average daily range of 3.5 oC (range 2.2-6.5 oC). Daytime Tb was positively related to ambient temperature(Ta), which ranged from -38 to -3 oC during the study period. Half of the monitored individuals that were provided with ad libitum food prior to and during Tb measurements were characterized by slightly but significantly warmer Tb than controls (38.3 vs. 37.9 oC) across the range of encountered Ta. Although Tb does not vary by much within and among individual red squirrels, its responsiveness to both ambient temperature and food availability demonstrates that shallow reductions in Tb are facultatively employed by red squirrels during cold periods of food scarcity.
