Reproductive Biology and Diets of Goannas (Reptilia: Varanidae) from Australia

Abstract

Aspects of the reproductive biology and diets of nine species of Varanus from the seasonal tropics and temperate zones of Australia were examined by dissection of 386 preserved museum specimens. We investigated whether morphological and habitat diversity in the varanids was expressed in reproductive and dietary diversity. Most species from seasonal tropical areas had enlarged testes in the dry season (June-October) and females with oviductal eggs were collected at the end of the dry season and the beginning of the wet season (September-January). However, three species seemed to be exceptions to this trend, with an extended reproductive season (V. storr), or reproductive activity in the late wet season (V. semiremex and V. kingorum). A diversity of reproductive seasons for varanids from seasonal tropical regions in Australia was also found in a review of the literature. Temperate zone species had enlarged testes in spring (September-November) and laid eggs in spring or late summer. Clutch sizes ranged from 1-7 eggs. Regression slopes of maternal SVL and clutch size seemed to be higher for the smaller-bodied species compared to the larger-bodied species, but sample sizes were too low to compare them statistically. A review of reproductive data on Australian varanids suggested that some large-bodied species (e.g., V. varius) had relatively small clutch sizes. Most species had generalized diets with lizards and orthopterans being the most important prey. Large-bodied species such as V. giganteus and V. glebopalma tended to eat larger prey items, and specialized on vertebrate prey. Varanus semiremex ate mostly aquatic prey. Diets were relatively similar for most species but appear to be influenced by body size and habitat.