Anthony Santoro

Globally, ~60% of freshwater turtle species are at risk of extinction. Knowledge about how freshwater turtles use aquatic and terrestrial habitats is lacking for most species. Moreover, there is minimal understanding of how environmental change will influence their behaviour and survival. Chelodina oblonga, a turtle species endemic to southwest Western Australia, exemplifies this extinction risk. This region is undergoing severe climatic drying, while within its capital, Perth, urbanisation has resulted in the modification or loss of >80% of wetlands. This project investigated how these stressors are affecting survival, recruitment, and viability of C. oblonga. I examined populations, with a focus on reproductive females, within a chain of three wetlands with variable hydrological regimes using a combination of radio-telemetry, field observations, and citizen science to: 1) develop an understanding of the strategies used to cope with the annual wet/dry cycle, 2) determine the species home-range and habitat associations, 3) determine the environmental factors that trigger nesting movements, 4) determine whether C. oblonga select specific habitats for nesting, and if so, what environmental variables are selected for, and 5) identify how the timing of hatchling emergence may be influenced by temperature and rainfall.

Adult female C. oblonga exhibited multiple behavioural and movement patterns and occupied small home-ranges within dense stands of native emergent macrophytes. Aestivation was an important survival strategy during two drying events. Aestivation lengths will need to extend to cope with the projected ongoing drying. Nesting movements were significantly associated with cold frontal weather systems and will be disrupted with projected alteration of front frequency and intensity. Chelodina oblonga exhibited selectivity for natural habitats when choosing nest-sites that are being consistently reduced with continued modification of wetland habitats. Hatchling emergence occurred within two periods associated with temperature and rainfall. Altered weather patterns may disrupt timing of hatchling emergence affecting survival. This study clearly identified the elements at all stages of C. oblonga’s life cycle under threat from both urbanisation and climate change, and proposes solutions to many of these threats. However, given the projected continuation of climate drying and urban development, significant adaptive management will be required to improve the species’ conservation plight.