HORMONAL INDEPENDENCE OF COURTSHIP BEHAVIOR IN THE MALE GARTER SNAKE

Garter snakes exhibit a dissociated reproductive tactic in which gonadal activity is minimal at the time of mating, increasing only after the breeding season has ended. Neither short-term nor long-term castration affects courtship behavior in adult male red-sided garter snakes (T. s. parietalis). So long as males have passed through a low-temperature dormancy period (hibernation), castration either shortly after emergence in the spring or before entering winter domancy in the fall does not prevent the display of intense courtship behavior on emergence. Males castrated during mating activity the previous spring prior to the annual testicular growth phase actively courted females on emergence from hibernation. Males adrenalectomized and castrated during low-temperature dormancy also courted females on emergence. Hypophysectomy during or before low-temperature dormancy did not prevent males from displaying high-intensity courtship behavior on emergence from hibernation. Other sides show that treatment with sex steroid hormones as well as by hypothalamic and pituitary hormones and a variety of neural and metabolic affectors also fails to elicit courtship behavior in noncourting males during the summer. Evidently causal mechanisms controlling courtship behavior in the red-sided garter snake are fundamentally different, at least at the physiological level, from those mechanisms are described for many laboratory and domesticated species.