Terrestrial habitat and individual fitness increase survival of a freshwater turtle in an urban landscape

Abstract

Urbanisation is causing rapid land-use change worldwide. Populations of freshwater turtles are vulnerable to impacts of urbanisation such as habitat loss, fragmentation and degradation, because many species require interconnected aquatic and terrestrial habitats. Understanding the processes that underpin survival in urban areas is critical in managing species that may vary in their responses to urbanisation. Here, we conducted a mark-recapture study of a common freshwater turtle (Chelodina longicollis) at 20 wetlands over five years across a broad geographical gradient in a large and expanding Australian city. Our aim was to examine relationships between survival and a broad suite of local and landscape environmental variables, and body condition. Using capture-recapture models, we found a positive relationship between the probability of survival of C. longicollis and the proportion of green open space in a 1-km radius around a wetland. There was a positive relationship between survival of female C. longicollis and body condition. Survival probabilities generally did not differ substantially among males, females or juveniles, or seasons. We found evidence of adult turtle mortality resulting from recreational fishing. Our results demonstrate the importance of terrestrial habitat surrounding wetlands for freshwater turtle survival in an urban environment. Our results suggest that management actions for C. longicollis in urban areas need to protect green spaces surrounding wetlands (e.g. parks and remnant vegetation) and discourage human actions that threaten turtle survival. Our study adds to mounting evidence that conserving freshwater turtle populations in urban areas requires managers to consider life cycle requirements over broad spatiotemporal scales.