Adaptations of Peromyscus for winter survival in an Appalachian montane forest

Both Peromyscus leucopus and P. maniculatus had slightly higher body mass in spring and summer than in autumn and winter. Mean resting metabolic rates of both species were highest in September and November. For both species, maximum nonshivering thermogenesis following norepinephrine dosage increase markedly in early autumn, declined in October and January following unseasonably warm periods, peaked in Febuary during the coldest portion of the winter, and declined throughout the spring. Neither length of photoperiod nor minimum ambient temperature correlated with the variation in resting metabolic rates, but both environmental factors correlated strongly with capacity for nonshivering thermogenesis. -Authors