REPRODUCTIVE PHYSIOLOGY OF THE BROAD BANDED WATERSNAKE , NERODIA FASCIATA CONFLUENS , IN SOUTHEASTERN LOUISIANA

—Reproductive cycles in temperate zone colubrid snakes are generally characterized by summer spermatogenesis (postnuptial) in males and spring vitellogenesis (Type I) in females. Watersnakes and gartersnakes in southern North America have shorter hibernation periods than confamilial northern species and potentially different timing of hormonal cues regulating gametogenesis. We studied the reproductive cycles of male and female Broad Banded Watersnakes (Nerodia fasciata confluens) to uncover whether hormone cycles are more similar to closely related northern natricine species or to more distantly related southern colubrids. We collected N. f. confluens from southeastern Louisiana and maintained them in outdoor enclosures. The first experiment quantified circulating sex steroid hormones, follicle growth, and presence or absence of sperm each month from February 2000 to February 2001. The second experiment measured the same variables weekly during the spring breeding season, from early April 2001 to late June 2001. Male androgen concentrations were elevated in the fall and the spring. Female estradiol-17 was elevated in the spring only. Ovarian follicle growth began in early May, after mating. The male reproductive cycle was classified as postnuptial spermatogenesis and the female cycle as Type I vitellogenesis; rapid follicle growth in the spring. Nerodia f. confluens has a reproductive pattern more similar to other southern temperate colubrids than to its more closely related northern temperate natricines, suggesting that local climate has a stronger influence on reproductive timing than phylogeny.