Testing the efficiency of thermal imagers for detecting arboreal marsupials in temperate forests

Context Wildlife monitoring must be cost-efficient due to constrained conservation budgets. Part of efficient monitoring is the selection of appropriate and effective methods for monitoring species. Aims In this paper, we evaluated the effectiveness of two methods (spotlighting and thermal imaging) for detecting four species of arboreal marsupial in the Strathbogie region of north-eastern Victoria, Australia. Methods We conducted 108 visits to 15 survey locations across the study area over the period of November 2017–June 2018. Each survey was conducted as a 250 m transect over 20–30 min. Occupancy modelling was used to evaluate the influence of observation method choice on detectability while accounting for other covariates. We calculated the expected minimum number of visits required to achieve a low (0.1) probability of failing to detect each of the four target species when present. Key results We found that spotlighting was best used for detecting greater gliders and ringtail possums, whereas thermal imagers were best for detecting mountain brushtail possums and koalas. Detectability estimates indicated that a minimum of three spotlighting or four thermal surveys should be planned. Conclusions The choice of method for detecting arboreal marsupials is dependent on several factors, including the body mass and eye shine of the target species. Covariates may play a part in detectability of some species, although the greater glider remains highly detectable regardless of the method. Implications Behavioural and physiological differences between arboreal species can influence the effectiveness of the survey method. Foraging activity and response to stimuli such as spotlights affect detectability and should be considered when planning survey methodology.