Effects of Pregnancy on the Body Temperature of the South American Rattlesnake, Crotalus durissus, in Southeastern Brazil

Abstract. Changes in the body temperature (Tb) of reproductive females are well documented in squamate reptiles. However, the direction of these changes varies among species. Pregnant females may exhibit a lower or higher (and less variable) Tb than nonpregnant females. In some species, pregnancy has no detectable effect on female Tb. In this study, we compared the Tb of female rattlesnakes (Crotalus durissus) in different reproductive statuses (pregnant and nonpregnant) to investigate whether pregnancy influences Tb. We measured the Tb of female rattlesnakes kept in a semi-natural outdoor enclosure during summer and spring 2016 and summer 2017. Pregnant females selected a higher mean Tb than nonpregnant females. Moreover, we found significant differences in Tb among seasons. Body temperatures in summer 2017 were higher than in other seasons; however, reproductive status did not influence Tb variance. Therefore, our results agree with the hypothesis that females change their thermoregulatory behavior during pregnancy. Female rattlesnakes may increase their Tb during pregnancy to increase offspring fitness or to maximize their lifetime fitness.