GONADECTOMY IN THE SPRING REINSTATES HIBERNATION IN MALE GOLDEN-MANTLED GROUND-SQUIRRELS

We tested the hypothesis that continued secretion of gonadal steroids is necessary to suppress hibernation in male golden-mantled ground squ irrels in the weeks after the terminal arousal in spring. Juvenile and adult-males were gonadectomized or sham gonadectomized 1 wk after the terminal arousal; 64% of castrated and none of the sham-castrated ani mals resumed hibernation. Latency to resumption of torpor was 9 +/- 2 days from the time of castration, and squirrels underwent 4.3 +/- 0.9 bouts before permanently regaining euthermia. Among squirrels that res umed hibernation, bout duration was significantly shorter and torpor w as shallower after castration. Castration as late as 3 wk after the te rminal arousal reinstated hibernation. We suggest that the terminal ar ousal of male squirrels in the spring is provoked by a steroid-indepen dent mechanism similar to that operating earlier in the hibernation se ason; abandonment of hibernation is contingent on concomitant sustaine d increases in androgen secretion during the first few weeks of euther mia.