Assessing the detectability of a cryptic arboreal marsupial by using a novel survey approach

Non-detection of a species arising from inadequate sampling effort or ineffective techniques, may have serious consequences for its conservation, particularly of those that are declining. The threatened and cryptic eastern pygmy possum (Cercartetus nanus), despite its widespread distribution, is infrequently detected using standard trapping techniques (e.g. Elliott traps and spotlighting). There are no survey guidelines for the species, and published literature suggest detection often requires significant survey effort and therefore cost. In this study, we investigated the detectability of the eastern pygmy possum by using wildlife cameras focussed on nest boxes and nectar food resources. We collected detection data in bushland remnants in northern Sydney over 5 years by using these methods and modelled detection probability. Detection probability was highest during winter in each year, which coincided with banksia flowering and breeding events, but detectability varied across survey years. We found that cameras targeting flowering banksia achieved a 95% detection probability from an average trapping effort of 117 camera nights, compared with 237 camera nights at nest boxes. We conclude that targeted use of wildlife cameras may be a cost-effective alternative to labour-intensive standard survey methods or to supplement existing survey approaches (e.g. nest box checks) and improve detection probability.