Reproductive Traits of Zoo-Bred and Wild-Bred Eastern Massasaugas (Sistrurus catenatus) at Species Survival Plan® Conservation Breeding Centres and Other Facilities.

Species recovery efforts may require establishment of ex situ populations to supply augmentation or reintroduction projects. The Eastern Massasauga (Sistrurus catenatus) is a small rattlesnake with an ex situ breeding program maintained by a consortium of conservation breeding centres. Small population size in human care has restricted the supply of animals for in situ conservation, thus, the development of improved ex situ breeding protocols was recommended. The objectives of our retrospective study were to (1) describe and compare reproductive traits between two groups of Massasauga litters born in human care: wild-bred litters (i.e., conceived in the wild) and zoo-bred litters, (2) test for factors associated with improved reproductive output in zoo-bred litters, and, (3) make recommendations for standardizing ex situ breeding protocols. Data were collected on Massasauga birth events that occurred from 2000 to 2020 at 13 North American zoos and partner facilities. Six outcomes related to litter size and survival of offspring were compared between zoo-bred (n = 43) and wild-bred litters (n = 51). Odds ratios were used to test for correlations between nine predictor variables and four response variables in zoo-bred litters. We found higher mean litter size and number of live young per litter in wild-bred litters (12 and 10, respectively) compared to zoo-bred litters (6 and 2). Wild-bred litters more often contained live young and less often contained unfertilized ova (98% and 34% of litters, respectively) than did zoo-bred litters (58% and 81%). Experimentation on the effectiveness of alternative mating practices is warranted to improve reproductive output in human care, thereby increasing capacity to support in situ conservation.