Sexual dimorphism, diet, and notes on reproduction in Oxyrhopus trigeminus (Serpentes: Colubridae) in the semiarid Caatinga of northeastern Brazil

Abstract

Selected morphological characters, diet, and reproduction of the false-coral snake, Oxyrhopus trigeminus, from several localities in the Caatinga region of northeastern Brazil are described based on examination of preserved specimens. Sexual dimorphism is evident, with females attaining larger body sizes than males, but males have relatively larger heads and tails. A total of 25 prey items was identified in 23 of the 97 O. trigeminus examined; based on the orientation of the prey in the stomachs, all items were ingested headfirst. Lizards are the most frequent prey (96%) of O. trigeminus, with the lizard Tropidurus hispidus being the most important prey species both in number and in volume; marsupials account for 4% of the diet. Juveniles have a narrower dietary niche width than adults, presumably because they have smaller mouths with a narrower gape. Females have a wider dietary niche than males, but there is a high niche overlap between the sexes; males and females do not differ in prey volumes. The analysis of the gonads showed that 10 females have 4-13 vitellogenic follicles (mean 7.8 ± 2.8 follicles), and 2 females have oviducal eggs, one with only one egg and the other with five eggs. The estimated minimum size at maturity for female O. trigeminus in the Caatinga is 400 mm.