Estimating the abundance of an endangered arboreal marsupial using camera traps and an integrated species distribution model

Estimates of population size are fundamental for the management and conservation of threatened species. The Mahogany Glider (<i>Petaurus gracilis</i>) is an Endangered marsupial endemic to the Wet Tropics of northeastern Australia. Despite its status, there is no reliable estimate of population size. In this study, we conducted camera trapping surveys for the species and employed a Bayesian integrated species distribution model (Koshkina et al. 2017; Fidino 2021) to derive population estimates. Presence-absence data from camera trapping surveys and presence-only data from historical sighting records were included in the integrated species distribution model. The model estimated median abundance at 6,036 , 4,834, and 2,820 individuals for home range estimates of 9, 16, and 25 ha, respectively. We suggest using the more conservative population estimate of about 2800 individuals, based on the 25 ha home range, because it likely best summarises density across the distribution. Using simulated data, we tested the effects of camera placement and subsampling, demonstrating that clustered camera arrangements and reduced sample sizes did not significantly affect model outcomes, with predictions primarily dependent on home range estimates. Our survey results suggest considerable spatial variation in glider density across its range. The population size estimates provide a baseline for future conservation initiatives and highlight the importance of ongoing monitoring and the application of advanced modelling techniques to inform species management.