Detection Probabilities for Three Nocturnal Floodplain Snakes: Implications for Monitoring the Endangered Grey Snake Hemiaspis damelii in the Murray‐Darling Basin

ABSTRACT

Snakes are experiencing global population decline due to habitat loss, environmental degradation, pollution and climate change, yet effective conservation is often hindered by their cryptic behaviour and low detectability. In this study, we conducted targeted surveys and estimated detection probabilities for the endangered grey snake ( Hemiaspis damelii ) and two sympatric species, De Vis' banded snake ( Denisonia devisi ) and curl snake ( Suta suta ), to inform planning under biodiversity offset schemes, future monitoring and conservation efforts in floodplain ecosystems of the Murray‐Darling Basin, Australia. Visual encounter surveys were conducted across 22 transects over 15 consecutive nights, resulting in 140 snake observations, including 15 new H. damelii records. Detection probabilities varied among species, with D. devisi exhibiting the highest detection probability (0.842), followed by H. damelii (0.582) and S. suta (0.430). The mean number of surveys required to detect each species with 95% confidence was two, four and six surveys, respectively. These findings emphasise the need to tailor survey effort to species‐specific detection probabilities to avoid false absences and improve the reliability of future surveys and monitoring programmes. We recommend integrating repeat surveys and occupancy modelling into standard monitoring protocols to improve conservation planning and management of threatened snake species. Our approach could be scaled to confirm grey snake presence at proposed development sites under biodiversity offset schemes by trading survey effort with spatial coverage to effectively sample extensive floodplain systems.