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

Abstract

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.

Distribution, habitat associations and status of the Carpentarian Pseudantechinus (Pseudantechinus mimulus, Dasyuridae)

“…Utilization of eastern and western aspects particularly may indicate of these slopes for basking towards sunrise and sunset respectively. This is a well-documented behaviour in P. macdonnellensis (Geiser et al, 2002;Geiser & Pavey, 2007;Pavey & Geiser, 2008), and it is likely that P. mimulus exhibits the same behaviour to at least some degree in the winter months (Barnes et al, 2023), when most field surveys during this study were conducted.…”

“…Sites were considered independent if they were at least 750 m apart, a distance chosen to maximize the independence of sites based on home range analysis of the congeneric P. macdonnellensis (Gilfillan, 2001b;Pavey et al, 2003). For more details, see Barnes et al (2023). All potential sites were field-verified for suitability based on visual assessment of the structure of rocky outcrops, as well as vegetation assemblage.…”

“…Each station was baited with approximately 125 g of peanut butter smeared directly onto the rock surface in the centre of the camera's field of view. For additional details, see Barnes et al (2023). The total survey effort from 2018 to 2021 was 28 767 trap-nights (Table 1).…”

“…An observed absence in our study therefore does not necessarily mean that a camera station has not historically been utilized by P. mimulus or will not be utilized by P. mimulus in the future. Despite this, our methodology relied on the best available guidelines for conducting camera trap surveys of the species (Barnes et al, 2023;Burnett et al, 2014) and we are confident that our results accurately reflect the true state of any given camera station during our study.…”

“…The holotype specimen of P. mimulus was originally collected from an unspecified location on 'Alexandra', a large pastoral holding in NT (Thomas, 1906) and, until 2012, the species remained rarely encountered, known from fewer than 50 records. Since 2012, the number of records of P. mimulus has increased to over 200, all within rocky environments in the Mount Isa Inlier Interim Biogeographic Regionalisation for Australian (IBRA) bioregion in QLD and the Gulf Coastal bioregion in NT (Barnes et al, 2023;Burnett et al, 2014Burnett et al, , 2015Kanowski et al, 2011;Lloyd et al, 2013;Sanders & Slater, 2004;Woinarski et al, 2011;Woolley, 2011).…”