ABSTRACT Urbanisation has a wide range of impacts on biological communities, which can affect individual animals' health and may lead to population declines if health effects cause decreases in lifespan or reproductive output. Here, health metrics of the southwestern snake‐necked turtle ( Chelodina oblonga ), a freshwater turtle endemic to and declining in southwestern Western Australia, were compared among populations from three wetlands in the Perth metropolitan area that differ in degree of urbanisation. In November 2023, 7–10 adult turtles were trapped in each of the three wetlands, scaled body condition was calculated, and a blood sample was collected from each individual to quantify blood glucose concentration and immune function, measured as bactericidal capacity, and baseline physiological stress level, measured as heterophil: lymphocyte ratio. There was no association between degree of urbanisation and any of the health metrics measured, suggesting that adult C. oblonga in populations from more natural habitats do not exhibit higher body condition, greater immune functioning or lower baseline physiological stress levels than adults from more disturbed habitats, and that impacts on individuals' health are likely not directly driving the apparent lack of recruitment observed in urban populations of this species. However, El Niño‐induced drought conditions during the sampling period may have placed additional environmental stress on all populations, not just those in more urbanised areas, potentially masking differences in health that may have been detectable in years more reflective of mean climatic conditions. An important next step is to quantify potential seasonal and interannual changes in health metrics across a wider range of populations and hydrological regimes to determine the magnitude to which drought conditions impact physiology in this species, the extent to which physiological plasticity may buffer individuals against negative health impacts, and whether physiological plasticity differs along a broader gradient of anthropogenic disturbance.
Refsnider et al. (Thu,) studied this question.