RHYTHMICAL AROUSAL FROM HIBERNATION IN THE GOLDEN-MANTLED GROUND SQUIRREL, CITELLUS LATERALIS TESCORUM

Abstract

Daily observations on each of over one hundred individuals of C. lateralis by a special technique indicated that no animal remains continuously in the hibernating state longer than approximately 16 days (at an environmental temperature of 32° F). The arousals were more frequent at the beginning (i.e. in the autumn) and the ending (i.e. in the spring) of the whole hibernating period, than during the middle of this period (December and January). Adult males were found to arouse more frequently than did adult females or the juveniles of either sex. Preliminary data indicate that arousals are more frequent the higher the environmental temperature (up to 70–75° F), Observations on 12 C. columbianus, 9 C. tridecemlineatus, and 28 Glis glis indicated maximum continuous hibernation periods of 19, 12 and 33 days, respectively, at an environmental temperature of 32° F; C. richardsonii did not hibernate under our laboratory conditions.The trigger which starts each arousal is not known. Food and water intake during an arousal is not necessary, nor is defecation. Urination, however, takes place during every arousal. The observations strongly suggest that the urine voided was formed only while the animal was in the active homothermic state. It is suggested that it is the accumulation of metabolic end products which constitutes the stimulus for an arousal.