Variation of rodents' body temperature across elevation in Alps

Understanding the physiological adaptations of animals living in mountain landscapes is a key to predicting the responses of individuals to environmental changes, especially those imposed by climate. In this regard, the mechanism of body temperature regulation is particularly important in determining the physiological limits for activity under hypoxic and climatic stressful conditions. Numerous studies have shown that body temperature of rodents and other animals decreases with elevation and with extreme winter temperatures. But surprisingly, it is still not known how body temperature of wild animals varies along elevation during their reproductive seasons. We studied variation in core body temperature among individuals (N = 294) of four rodent species (Apodemus flavicollis, Apodemus sylvaticus, Apodemus alpicola, Myodes glareolus) and its association with elevation (from 400 to 1,822 m asl), accounting for variation in environment temperature, microhabitat structure, body condition, and sex. Results showed a strong positive effect of elevation and a more limited effect of environmental temperature on rodents’ body temperature during spring and summer. The effect of elevation on body temperature was influenced neither by interactions with environmental temperature or sex nor by the microhabitat structure. We suggest that in normothermic condition at high elevations, small mammals experiencing hypoxic exposure might show physiological adjustments for increasing efficiency of thermoregulation in low oxygen conditions.