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.

Persistent Tolerance to Oxygen and Nutrient Deprivation and N-methyl-D-Aspartate in Cultured Hippocampal Slices from Hibernating Arctic Ground Squirrel

“…Shavings are placed on the back of the AGS and checked every 24 h. An AGS is considered 'torpid' (hibernating) if the shavings remain on its back or considered to have been through an 'arousal' if the shavings are disturbed or missing. This 'shavings added' or 'sawdust method' is a reliable indicator of hibernation (Lyman, 1948;Pengelley and Fisher, 1961;Willis et al, 1971). Additionally, RR and responsiveness of each AGS were recorded daily for further validation of the hibernation state.…”

Circulation in Mammalian Hibernation

“…The golden hamster may average three days in hibernation between arousal, while the average for the thirteen-lined ground squirrel is closer to six or seven days (Pengelley and Fisher, 1961), and bats remain torpid for more than a month. Kayser (1952) has shown that bouts of hibernation are longer during the middle of the hibernating season and this has been confirmed by Pengelley and Fisher (1961).…”

“…The cause of natural arousal is a mystery, though Strumwasser (1960) has shown that it occurs at the same time of day in the California ground squirrel which is starting the hibernating season, as if the stimulus was mediated by some sort of temperature independent biological clock. Many other hibernators demonstrate no particular diurnal pattern in arousal time, but arousals take place at fairly regular intervals (Pengelley and Fisher, 1961).…”

“…Many animals, notably some species of ground squirrels (Pengelley and Fisher, 1961), are very seasonal in their cycle. During the spring and summer they cannot be made to hibernate when exposed to cold and maintain as regular a body temperature as the common nonhibernating laboratory animals of the same size.…”

Periodic arousal from hibernation is necessary for initiation of immune responses in ground squirrels

“…They sustain elevated T b s for Ͻ1 day, after which they return to hibernation (21,53,71). Up to 80% of a hibernating mammal's winter energy budget is consumed during these periodic arousals (9,35,66), and the consequent depletion of energy stores may contribute to overwinter mortality (71).…”