Reproduction and Seasonality in Snakes

Of the nearly 3,000 snake species worldwide, the International Union for the Conservation of Nature (IUCN) names 80 on its Red List of Threatened Species, a number widely thought to be an underestimate due to lack of information on the status of many species. However, there are currently only four Species Survival Plans for snakes, none of which are actively involved in germplasm cryopreservation.

Surprisingly, even basic semen parameters are unknown for all but five of the world’s snake species. To begin to remedy this dearth of knowledge, we initiated a project to gather reproductive data and develop assisted reproductive technology using local Southern California snakes on the grounds of the San Diego Zoo's Wild Animal Park. Semen collected by ventral massage was cryopreserved with increasing success. Vitellogenesis was observed by ultrasound and the seasonality of ovum growth and ovulation and gestation was recorded. During the year of the initial study, 78 male and 44 female snakes of 14 species were caught at the Wild Animal Park, and reproductive data were collected on 62 males and 35 females (a 79- and 80-percent success rate for males and females, respectively). In addition, 14 of 20 semen collection attempts in males from the San Diego Zoo’s Herpetology Department resulted in analyzable samples.

This project established a new area of research at CRES, and protocols developed during this ongoing study will be applied to related endangered species of snakes in the Zoological Society of San Diego's collection. In addition, publication of these data will fill a conspicuous gap in the international conservation literature, where no work of this kind has been reported.