A study of the ecology of Krefft's River Tortoise, Emydura krefftii, was conducted in the tea-coloured perched lakes of Fraser Island, from March, 1977. to September, 1979. The principal aim was to bring ecological knowledge of Emydura krefftii, a species that has received very little attention in the past, to par with that of other Australian chelids.
The approach to the study was distinctive, in that it involved an intensive mark-recapture programme, with traps set for fixed periods of time on a regular grid — an approach not often adopted in studies of chelonian ecology. The mark-recapture programme, supplemented by sonic tracking and casual observation, provided detailed information on the spatial and temporal distribution of activity, on the movement patterns, and on the population structure and dynamics of a population of Emydura krefftii. An analysis of the annual growth cycle and long-term growth of the turtles is also presented. The dissection of specimens and histological examination of their gonads, yielded information on the sexual maturity, the seasonal cycles of spermatogenesis and vitellogenesis, and the reproductive potential of the species. The reproductive strategy of Emydura krefftii is discussed in the context of knowledge of the reproduction of other species of freshwater turtle. An analysis of stomach contents provided data on the composition of the diet of Emydura krefftii, and data on the variation in diet with turtle body size and sex.
Emydura krefftii, as a representative of its genus, is ecologically distinct from species belonging to other Australian chelid genera — especially in terms of diet and habitat preferences. In more general terms, the present study supports the conclusion of others, that there are few ecological features of the Australian pleurodires that do not find counterparts among the cryptodires of the Northern Hemisphere. Ecologically, the pleurodiran genus Emydura most closely resembles the cryptodiran genus Chrysemys (= Pseudemys), of the family Emydidae.
Emydura krefftii proved remarkably abundant in an environment generally considered to be nutrient-deficient and of low productivity — the perched dune lakes of Fraser Island. Its success is explained in terms of its catholic diet (including foods of terrestrial origin), its reproductive strategy, and features of its unusual environment. With a density of 87 turtles/ha, representing a biomass of 28.8 kg/ha, Emydura krefftii is considered to be the dominant vertebrate species of the perched dune lakes.