Ecological Ramifications of Prey Size: Food Habits and Reproductive Biology of Australian Copperhead Snakes (Austrelaps, Elapidae)

Abstract

Dissection of 641 specimens of three species of Austrelaps provided data on body sizes, sexual dimorphism, food habits, and reproductive biology. These snakes are large elapids of cool to cold climates in southeastern Australia. Australian elapids mainly eat small prey, and foraging theory therefore predicts that they should be relatively unselective with respect to prey type and prey size. The diet of copperheads is very broad, including most of the locally available terrestrial vertebrates. Of 216 prey items, 66% were scincid lizards and 27% were frogs. Most prey items were very small, and there was no apparent relationship between prey and predator sizes. The proportion of snakes containing prey was consistently lower in juveniles than in adults, and lower in gravid females than in non-gravid females. Austrelaps ramsayi and A. superbus are similar in body size, with A. labialis much smaller: all are similar ecologically. Males grow much larger than females, and are more numerous in museum collections. All three species are viviparous, with ovulation in spring and parturition in late summer. Only about two- thirds of adult-size females collected in summer were reproductive, suggesting that individual females may not reproduce every year. Litter sizes varied from 3 to 32, with means of 7.4 in A. labialis, 14.6 in A. superbus, and 15.0 in A. ramsayi. The lower fecundity in A. labialis is attributed to smaller maternal body size: the relationship between maternal SVL and litter size is similar among the three species. Size at birth Australian elapids mainly eat small prey, and foraging theory therefore predicts that they should be relatively unselective with respect to prey type and prey size. The diet of copperheads is very broad, including most of the locally available terrestrial vertebrates. Of 216 prey items, 66% were scincid lizards and 27% were frogs. Most prey items were very small, and there was no apparent relationship between prey and predator sizes. The proportion of snakes containing prey was consistently lower in juveniles than in adults, and lower in gravid females than in non-gravid fe- males.