ABLATION OF SUPRACHIASMATIC NUCLEUS ALTERS TIMING OF HIBERNATION IN-GROUND SQUIRRELS

Hibernation patterns were monitored continuously for 2.5 years in fema le squirrels that were neurologically intact or in which the hypothala mic suprachiasmatic nucleus (SCN) was completely ablated (SCNx). The n umber of hibernation bouts in SCNx squirrels increased by 159%, total hibernation time increased by 58%, and periodic arousals from hibernat ion were 47% longer in SCNx than in control squirrels; the duration of individual torpor bouts was 2 days shorter and far more variable in S CNx than in control animals, Some SCNx squirrels cycled through bouts of torpor continuously for nearly 2 years. The SCN appears to be part of the mechanism that controls the duration of the hibernation season and the temporal structure of individual torpor bouts.