Optimising camera trap surveys for the Carpentarian Pseudantechinus (Pseudantechinus mimulus) in northwest Queensland

The Carpentarian Pseudantechinus (Pseudantechinus mimulus) is a poorly studied dasyurid marsupial that inhabits rocky outcrops in the Mount Isa Inlier bioregion in Queensland and the Gulf Coastal and Gulf Fall and Uplands bioregions in the Northern Territory. It is readily detected by passive infrared triggered camera traps (‘camera traps’). Camera trap data can be used to develop detection probability estimates from which activity patterns can be inferred, but no effort has previously been made to determine changes in the detectability of P. mimulus throughout the year. We undertook a 13-month baited camera trap survey across nine sampling periods at 60 locations of known historic presence or nearby suitable habitat to assess the change in detection rates and detection probabilities of P. mimulus across a year. Detection probabilities were calculated from camera trap data within a single-species, multi-season occupancy framework to determine optimal survey timing. Detection probability data were used to calculate the likelihood of false absences to determine optimal survey duration. We recorded 2493 detections of P. mimulus over 10 966 camera days. Detection probability ranged from 0.009 to 0.179 and was significantly higher from April to October than from November to March. The likelihood of false absences varied by sampling period and desired level of confidence. We find that camera trap surveys for P. mimulus are best conducted from April to October, but optimal survey duration is dependent upon the time of year and desired level of confidence that an observed absence from a given site reflects a true absence at that site. Attaining a minimum of 80% confidence of absence requires as few as 9 days of survey effort in May to 16 days of survey effort in October.