Body mass and growth rate of zoo-housed eastern massasauga rattlesnakes Sistrurus catenatus: implications for ex situ conservation programs

Abstract

The eastern massasauga Sistrurus catenatus is an at-risk pygmy rattlesnake species experiencing decreasing populations in the wild. These declines have led to the establishment of ex situ conservation programs in accredited zoos. Information related to body size and growth are critical for the success of ex situ conservation programs, but there is a lack of physiological research into zoo-housed massasauga populations. This study aimed to: 1) determine average body mass and growth rate across growth windows, and 2) determine which factors (sex, institution, origin) influence the size and growth of eastern massasaugas in zoos. A total of 76 females and 94 males (N=170) born between 2000-2021 across 18 institutions were analysed from the Species360 Zoological Information Management System (ZIMS). Results indicated that average body mass was not different between the sexes in any of the growth windows. The average mass of neonates at birth was not different between females and males. The growth rate was highest during the 12-35 month period of life, where females experienced a higher growth rate than males. Institution significantly affected both mass and growth rate. The origin of snakes (wild vs. zoo) affected birth mass and early growth rate, but not overall body mass in any window. Comparison to the literature indicated zoo-housed adult eastern massasaugas are heavier than wild individuals. These findings reveal important allometric information about the eastern massasauga rattlesnake that can inform zoo husbandry practices to improve animal health and wellbeing, and contribute to breeding success.