Detecting possums at very low densities following control

Abstract

The research, above, has three key conclusions. First, the thermal cameras consistently had higher detection rates than chew cards and PIR trail cameras. They provide increased monitoring sensitivity and the ability to record animal behaviour around monitoring or control devices. While more expensive than PIR trail cameras, their cost-effectiveness will ultimately be determined by comparing the ongoing costs of sorting and categorising the images. Future research for both is ongoing and should improve (Ross 2021). Second, the combination of GPS, PIR trail cameras and thermal cameras has provided crucial information on the encounter and interaction rates. While using only a 21-day window, the results suggest that a monitoring grid of 1 device per 25 ha should reliably detect most animals over this time period. Encounter rates may be higher at lower possum densities as home range size increases as animals are removed (Whyte et al. 2013). Additionally, encounter rates may be higher for monitoring and control devices left out longer; however, this will increase costs with additional service requirements. Third, this research has highlighted a concern around trap interaction rates. Increasing interaction rates for traps is a developing research topic. Project Cacophony is developing higher interaction traps using open architecture and hazing (Traps powered by Artificial Intelligence – 2040). Zero Invasive Predators have developed auto-feeding lures, which have a 12-month field life before servicing is required (ZIP MotoLure — Zero Invasive Predators). In addition, PFNZ2050 has funded a PhD student at Lincoln University to investigate the influence of social, visual, and audio sounds combined with auto-feeding food lures to improve possum interaction rates. This research will involve Predator Free Banks Peninsula, and we will be able to determine interaction rates for these new tools as they attempt to eradicate possums from Banks Peninsula's 'Wildside' area.