Comparison of sympatric freshwater turtle populations from an urbanized Sydney catchment

1. Australian freshwater turtles are widely distributed throughout the continent, and in each river catchment there are at least two taxa. In south-eastern Australia Chelodina longicollis and forms of Emydura macquarii cohabit within a waterway, although they have been shown to partition habitat within the water column in non-urban bodies of water. Limited comparative data are available for the urban populations. 2. Within urban Sydney C. longicollis (eastern long-necked turtle) and Emydura macquarii dharuk (Sydney short-necked turtle) share habitat. However, in contrast with non-urban studies of C. longicollis and other sympatric E. macquarii taxa, it was observed that the population profile of the two species was similar at all sites, and that C. longicollis were present in greater numbers than E. m. dharuk. 3. The continued degradation of preferred habitat, low recruitment, and potential competition from introduced turtles place both species in a precarious position. 4. The shallow, impounded waterways of the regulated urban bodies of water align more closely with the preferred habitat of C. longicollis than with that of forms of E. macquarii, which prefer deeper flowing waters or large wetlands adjacent to rivers. Emydura m. dharuk may be at greatest risk of extinction in urban areas. 5. Across urban Sydney, the low numbers of E. m. dharuk compared with C. longicollis may be due to the lack of mobility of E. m. dharuk such that individuals tend to be stranded in sub-optimal habitat. In contrast, C. longicollis has a greater propensity for overland movement, and a preference for the 'new habitat' resulting from urban impacts on the associated waterways, and thus appears to be able to utilize these modified urban waters more successfully.