Seasonal Changes in Body and Adrenal Weights of Chipmunks (Eutamias)

Body weights of Eutamias amoenus luteiventris (Allen) and Eutamias minimus oreocetes Merriam collected in western Alberta were low in April on emergence from hibernation and increased through May and June to a constant summer level. Adrenal weights were also low at the time of spring emergence but increased steadily, reaching a peak in July and August. In the case of breeding males, this seasonal increase in adrenal weight was delayed until the breeding season had ended but increase was rapid thereafter and relative adrenal weights of breeding males were comparable with those of the rest of the population by July. Limited data suggest a decrease in adrenal size before hiber¬nation. Seasonal changes in adrenal weight may be related to seasonal changes in social interaction but could just as readily be related to other seasonal variables such as reproduction, hibernation, food-gathering activity, length of foraging move¬ments, and density of vegetative cover.