Ecology of the snake Atractus paraguayensis (Dipsadidae) in southern Brazil

Knowledge of snake ecology is important to support conservation strategies. Atractus paraguayensis Werner, 1924 is a dipsadidae with semi fossorial habits distributed throughout southern Brazil. We analyzed the morphology, seasonality and reproductive biology of this species in a subtropical area in southern Brazil by combining material from scientific collections and field data. We found that females have a larger body size than males and that the reproductive cycle of females is seasonal, with vitellogenesis occurring in the warmer months of the year. Males exhibited no differences in testicle volume throughout the year; however, mating likely occurs in the spring when males are more active. Recruitment of newborns occurs in late summer. The number of individuals collected during the hottest months (September through February) was significantly higher than the number of individuals collected during the colder months. Our results, which reveal sexual dimorphism in the species and seasonal breeding restricted to warm months, contribute important information about this species’ biology.