SEASONAL-VARIATIONS IN CIRCADIAN-RHYTHMS PERSIST IN GONADECTOMIZED GOLDEN-MANTLED GROUND-SQUIRRELS

Circadian wheel-running activity was monitored in intact and gonadecto mized female and male golden-mantled ground squirrels maintained in a 14L:10D photoperiod at 21 degrees C. Marked advances in phase angle of activity onset and increases in the duration of the daily active phas e occurred each year in intact animals coincident with the phase of re productive activity. Surprisingly, longterm gonadectomized squirrels o f both sexes manifested similar seasonal changes in the circadian syst em. Seasonal circadian variations in locomotor activity are generated by a circannual clock independent from and not influenced by concurren t changes in secretion of gonadal hormones.