Abstract
Human activities and climate change are altering wetland hydrology, potentially affecting freshwater turtle habitats. Understanding freshwater turtle habitat requirements is important for conservation. Chelodina oblonga, a freshwater turtle endemic to southwestern Australia, inhabits wetlands undergoing hydrological changes due to reductions in rainfall and urbanisation. Urban populations of C. oblonga are declining, but limited knowledge of their habitat requirements hinders conservation efforts. This study used radio-telemetry to determine the habitat associations of 100 adult female C. oblonga in three urban wetlands with varying hydrological regimes between 2018 and 2020. During wetland inundation, turtles occupied dense stands of two emergent macrophytes: Typha orientalis (naturalised, invasive) and Machaerina articulata (native). When wetlands dried, turtles aestivated in shallow areas beneath these plants, contrasting with previous reports that aestivation occurred within the deepest areas. As inundation was the trigger for emergence from aestivation, some individuals in the shallowest areas aestivated for > 581 consecutive days and missed a reproductive season. This study indicates that complex vegetation is key aquatic and aestivation habitat for female C. oblonga, and alterations to hydro-regimes, particular increased drying, may have severe implications for isolated freshwater turtle populations through limiting recruitment. Hydrological regimes that incorporate an annual wetted period are recommended for conserving C. oblonga, in view of projected ongoing drying of wetlands due to climate change. Maintenance and restoration of dense emergent macrophyte stands, preferably the native M. articulata, is recommended to help conserve C. oblonga populations in wetlands that regularly retain surface water in the future.
