Pinealectomy blocks vernal courtship behavior in red-sided garter snakes.

Male red-sided garter snakes (Thamnophis sirtalis parietalis) court only on emergence from winter dormancy. The salient proximate factor responsible for the initiation of courtship behavior appears to be warm ambient temperatures subsequent to sustained exposure to cold temperatures. In the present study, autumn-captured garter snakes were pinealectomized or sham-pinealectomized 1-2 weeks prior to hibernation. After 17 weeks of maintenance in several ambient lighting and temperature conditions, all males were tested for the presence of courtship behavior. No pinealectomized animals exhibited any indications of reproductive behavior, whereas 53% of sham-pinealectomized males actively courted females. Photoperiod did not influence the prevalence of mating behavior. These results suggest that the pineal gland mediates non-photoperiodic seasonal information in the garter snake. This is the first demonstration, in any vertebrate species, that the pineal gland can directly influence reproductive behavior.