Figure 1. Camera trap locations in the Meehan Range (purple diamonds). Green shading indicates potential sugar glider habitat (eucalypt forest) and dark grey represents unsuitable habitat (cleared land). Elevation ranged from 290-400m above sea level.
Animal trapping – Between the 14-21st September 2021, 24 Mawbey traps (Mawbey, 1989) were deployed across the study area spaced 50-100m apart. Traps were fixed to wooden platforms deployed at heights of 3-6m on eucalyptus trees. The trap entrance faced the tree and was spaced approximately 15cm from the trunk. Each trap was baited with standard bait and the trunk was sprayed with a honey-water solution up to six metres high. Traps were checked in the early morning, but no sugar gliders were captured over 168 trap nights using this approach. We also surveyed swift parrot nest boxes previously deployed in the study area and caught eight sugar gliders in February (n=4) and September 2021 (n=4). We gave each animal an unique ear notch with a 2mm ear punch per Gracanin et al. (2022). Only resighted uniquely marked gliders could be incorporated in to SECR analyses and unsighted marked animals were excluded due to the haphazard marking of so few animals and lack of verification of them being at the study site once the SECR study started. After a blinded trial aimed at verifying that sugar gliders can be distinguished from one another (Supporting Information), we employed ‘selfie-trap’ methods by (Gracanin et al. , 2022) to visually identify unmarked individuals on camera.
Camera trapping – We conducted two camera-trap surveys with different baits to study the glider population. In Spring 2021 (September-November), a 30-night honey-baited survey and a 30-night fish-baited survey were conducted consecutively. The ‘honey-bait’ survey ran from September 21st to morning of October 21st. The ‘fish-bait’ survey ran from the evening of October 21st to November 20th. The ‘honey-bait’ survey used standard bait (honey, oats and peanut butter; weight ratio 1: 4.5: 2.5) since it was the most prevalent bait in the literature, and a honey-water solution lure (volume ratio 1:4). The ‘fish-bait’ survey used a fish (tuna and pilchard) oil, oat and peanut butter bait mixture (weight ratio 1: 4.5: 2.5) and a fish oil-water emulsion lure (volume ratio 1:5). We selected fish oil because it is common in predator baits (Commonwealth of Australia, 2011) and has inadvertently attracted sugar glider bycatch previously (Fairbridge et al. , 2003, Lindenmayer et al. , 2016).
The camera-trap locations (n=39) were consistent across both surveys. Camera-traps were set up in three arrays ~200m apart and the cameras were ~50m (mean 49.8m) apart within arrays (13 per array) (Fig.1). This spacing was based on Gracanin & Mikac (2022b) who showed a 100m separation was too distant to obtain enough recaptures at multiple camera traps.
Cameras were installed using the ‘selfie-trap’ method (Gracanin, Gracanin & Mikac, 2019). This incorporates a motion-activated infrared video camera positioned at the end of an open PVC pipe that is directed towards a bait holder secured at a close focal range. The camera was amplified with a +400 lens attached to the camera to ensure videos were in focus at the point of interest (i.e. the bait holder). The pipe, containing camera and bait, was secured to a wooden platform and fixed to trees at 3-6m height. We used Browning video cameras (30 x Recon Force 4K BTC 7-4K, 9 x Edge Spec Ops BTC-8E) and settings recommended by Gracanin et al. (2022).
Bait balls were inserted into perforated containers that restricted access by sugar gliders to prevent total consumption of bait. The liquid lures were sprayed on the tree trunk above and below the camera. We replaced baits and resprayed trees mid-way through each survey (day 14-16).