Energetics of hibernation in the Arctic ground squirrel (Spermophilus parryii kenicotti)

Abstract

Arctic ground squirrels (Spermophilus parryii kenicotti) hibernate underground; experiencing burrows temperatures of -5 to -25C̊. Hibernation consists of 7-9 months of torpor interrupted every 2-3 weeks by 10-20 h arousal episodes with high body temperatures and metabolic rates. Metabolic rates and body temperatures were measured during arousal episodes under temperate and arctic conditions. No difference in cost of arousal episodes was detected. Yet, when the cost of thermogenesis during torpor was included, proportional cost of arousal episodes decreased from 86 to 27% comparing temperate to arctic conditions. The relationship between metabolic rate and body temperature was examined during the recooling phase of hibernation. As animals entered torpor, body temperature was allowed to either decrease naturally or was experimentally altered at different points along the recooling curve. The changes in metabolic rate can be explained by changes in body temperature and no sign of temperature-independent metabolic suppression was detected.