Facilitation of courtship behavior in the male red-sided garter snake (Thamnophis sirtalis parietalis) following lesions of the septum or nucleus sphericus.

Courtship behavior in male red-sided garter snakes is limited to the period immediately following spring emergence. Lesions of the septum or nucleus sphericus prior to hibernation facilitate courtship behavior upon emergence the following spring. These lesions also had a significant effect on the reproductive physiology of the male snake. Snakes with lesions in the nucleus sphericus had a significantly higher concentration of circulating androgens compared to the control group. While animals with lesions in the septum exhibited elevated levels of circulating androgens, they were not statistically elevated when compared to the control group. The quantity of sexual granules in the epithelium of the renal sexual segment, a secondary sexual characteristic of male squamate reptiles, was significantly greater in lesioned animals. These results are the first to demonstrate a central inhibitory control of sexual behavior in a snake.