The swamp racer Mastigodryas bifossatus is a large colubrid snake distributed mainly in open areas in South America. Dissection of 242 specimens provided data on body sizes, sexual size dimorphism, reproductive cycles and food habits of this species. Adult M. bifossatus average approximately 1100 mm in snout–vent length, with males and females attaining similar sizes. Reproductive cycles in females seem to be continuous, although oviductal eggs occur mainly from the beginning to the middle of the rainy season with peak recruitment at the end of the rainy season. Clutch size ranges from four to 24 and each newborn individual is about 300 mm SVL. Mastigodryas bifossatus is euryphagic, feeding mainly on frogs (44%) and mammals (32%). Lizards (16%), birds (4%) and snakes (4%) form the remaining prey. Relatively small prey (0.05–0.019) are ingested by adults, and juveniles eat mammals, which suggests that there is no ontogenetic shift in the diet of this snake. Swamp racers forage by day on the ground in open areas but may use arboreal substrates for sleeping or basking.
The Herpetological Journal is an international scientific journal that publishes papers on the natural history of amphibians and reptiles. Experimental, observational and theoretical studies are published along with reviews and book reviews. Faunistic lists, letters and results of general surveys are not published unless they shed light on herpetological problems of wider significance.