Sexual dimorphism and reproductive ecology of the South American rattlesnake Crotalus durissus (Squamata: Viperidae) in the Brazilian Cerrado

The South American rattlesnake (Crotalus durissus) is widely distributed in Brazil, including isolated populations in savannas within Amazonian and Atlantic forests. We investigated the sexual dimorphism and reproductive ecology of C. durissus from the Brazilian Cerrado to address the following questions: (1) What patterns of sexual dimorphism in morphometric characters are present? (2) Do sexes differ in size at sexual maturity? (3) Does reproduction of males and females vary seasonally? (4) Do females reproduce annually, biennially, or at longer intervals? We found sexual dimorphism with males having larger body sizes and longer tails than females, a pattern likely associated with intra-sexual competition between males. Males reach sexual maturity at a slightly smaller size than females (60.7 vs 62.7 cm snout–vent length). In females, vitellogenesis peaks in the late dry season (September), extending into the early rainy season (October–November). The female reproductive cycle suggests a biennial or more extended pattern, as seen in other rattlesnake species. Males show testes with a turgid appearance and convoluted vas deferens year round.