Food habits and reproductive biology of the endemic melanesian elapids: are tropical snakes really different?

Do the ecological traits of tropical snakes differ from those of temperate-zone species? We examined preserved specimens in museums to quantify body sizes, sexual dimorphism, dietary habits, and reproductive cycles of the proteroglyphous snake lineages endemic to New Guinea and the Solomon Islands for comparison with previously-studied Australian and Asian species. The Melanesian snakes comprise a diverse group in terms of body sizes (adult sizes from <50 cm to >1 meter), body shapes (slender to heavy-bodied), and behavior (nocturnal to diurnal). Males attain larger sizes than do females in Aspidomorphus and Micropechis, but the reverse is true in Loveridgelaps, Salomonelaps, and Toxicocalamus. Aspidomorphus and Toxicocalamus show significant sex differences in relative head length, but species in the other genera do not. All taxa for which we have data on reproductive mode are oviparous, and produce an average of 3 to 9 large eggs per clutch. Relative to maternal body sizes, Melanesian elapids have significantly smaller clutches than do Australian elapids. The two smaller-bodied genera showed dietary specialisation (on earthworms by Toxicocalamus, and on skinks by Aspidomorphus). Toxicocalamus and the Fijian Ogmodon are thus the only Old World elapids to specialise on invertebrate prey. The larger-bodied taxa (Loveridgelaps, Micropechis, Salomonelaps) have more generalised diets, consisting primarily of lizards and frogs. The distinctive features of the Melanesian elapid fauna (low fecundity in all taxa, and earthworm-eating by Toxicocalamus) may reflect adaptations to tropical habitats, but generalizations about the ecological adaptations of tropical snakes remain elusive.