Diet and feeding behavior of Helicops infrataeniatus (Serpentes: Colubridae: Xenodontinae) in southern Brazil

Analysis of the gut contents of 278 specimens of Helicops infrataeniatus from the eastern Central Depression of Rio Grande do Sul state, Brazil, indicates that this species feeds on fish and frogs. Fish were found in 60.0% and amphibians in 40.0% of the specimens with identifiable stomach and/or intestine content (n=34). Fish corresponded to 69.5% and amphibians to 30.5% of the consumed items. Representatives of seven families and 10 genera of fish, from diverse microhabitats were identified. Among the amphibians, metamorphosed leptodactylids (two species of Leptodactylus and one of Pseudopaludicola) and a hylid tadpole were found. These data and field observations indicate that the species may forage in several water strata and at water's edge, during the day and/or at night. The predator-prey size relationship is weak, but positive and significant (r(2)=0.3228, P<0.001), indicating that large individuals of H. infrataeniatus generally ingest larger prey items. Eighty seven percent of the prey had a total length from 5 to 15% of the snout-vent length of the snakes that ingested them. Large prey, relative to snake size, were generally swallowed headfirst, whereas relatively small prey were swallowed head or tail first. The single exception was a large elongate (ophioform) fish without spiny fins: an easily swallowable and harmless prey, that was swallowed tail-first.