Radiotelemetric assessment of diel cycles in euthermic body temperature and torpor in a free-ranging small mammal inhabiting man-made nest sites.

Five free-ranging white-footed mice, peromyscus leucopus, known to inhabit man-made nest boxes were captured during winter, surgically-implanted with temperature-sensitive radiotelemeters, and released at the site of capture. The body temperatures of mice which voluntarily inhabited nest boxes were monitored from a remote location with an AM receiver on 17 days.All five mice were able to maintain stable euthermic body temperatures (approximately 35-37°C during the day; 37-39°C at night) during exposure to subfreezing ambient temperatures. Two body temperature profiles of daily torpor were obtained from one animal. On both occasions, the mouse entered torpor approximately 2 hours before sunrise, maintained a minimum body temperature of 18°C, and was fully aroused by 1500h.The influence of thermoregulation (during euthermia and torpor) on energy expenditure and survival in free-ranging mice is discussed.