Hormones and reproductive cycles in snakes

Although progress has recently been made in understanding the role of hormones in regulating the reproductive cycles of snakes, many of the gaps highlighted in the first volume of this book remain to be addressed. Studies continue to disproportionately examine temperate zone viperid and colubrid snakes, especially the red-sided garter snake (Thamnophis sirtalis parietalis). Extensive observational and experimental studies on T. s. parietalis form the basis for our understanding of the hormonal regulation of reproduction in snakes. This chapter focuses on seasonal hormone concentrations in snakes in relation to events in the reproductive cycle; the limited data available on hypothalamic hormones, gonadotropins, hormone receptors, and binding globulins; the neuroendocrinology of reproduction; and the environmental, social, physiological, and embryonic aspects of hormonal regulation of reproduction in snakes. We conclude with a discussion of how endocrine physiology can inform conservation and suggestions for future research. Specifically, to provide a basic understanding of the hormonal regulation of reproduction in this highly diverse group of animals, we stress the importance of future work that (1) examines a more diverse ecological and taxonomic representation of snakes, (2) includes experimental studies on the effects of hormones on reproductive tissues and behaviors, and (3) elucidates important components of the neuroendocrinology of reproduction.