Diet of Two Freshwater Turtles, Chelodina rugosa and Elseya dentata (Testudines: Chelidae) from the Wet-Dry Tropics of Northern Australia

Abstract

Chelodina rugosa occupies seasonally ephemeral waterholes on the coastal freshwater floodplains of the wet-dry tropics of northern Australia. It is an obligate carnivore and feeds primarily on fish, fast-moving aquatic invertebrates, and carrion. Differences between wet-season and dry-season diets, notably an increase in fish consumption and a decrease in consumption of odonate nymphs, reflect changes in abundance or accessibility of prey items. Elseya dentata occupies permanent water riverine habitats and is primarily herbivorous. The bulk of its diet consists of fruit and leaves of riparian rainforest trees, and seasonal changes in fruit species consumed reflected fruiting patterns. Filamentous algae comprised 30% by mass of the dry-season diet but was absent from the river during wet-season flooding and hence was absent from the diet. Elseya dentata readily feed on meat and fish carrion when available, but animal prey such as shrimp (Macrobrachium sp.) and freshwater sponge formed only a small proportion of their diet. Because E. dentata relies on riparian trees for most of its dietary intake, it is extremely vulnerable to land management practices that have adverse impacts on riparian forests.