A comparison of lure types and monitoring methods in wētāpunga (Deinacrida heteracantha) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Albany, New Zealand
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2023
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Massey University
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Abstract
Novel predators are one of the largest drivers behind insect population declines and extinctions. This is particularly true for New Zealand insect species as the lack of a mammalian predator archetype throughout their evolutionary history has resulted in many large-bodied, flightless, and nocturnal species. New Zealand wētāpunga populations have suffered large population declines due to novel predators and are now restricted to off-shore, pest-free islands. Currently lacking are reliable and non-lethal methods available to monitor wētāpunga and other large bodied wētā populations. In my thesis, I review the direct and indirect impacts of novel predators on native species and how variation in prey naivety results in behavioural trade-offs, for example between antipredator behaviours and foraging. The data chapters in my thesis test two aspects of wētāpunga monitoring: lure attractiveness and the effectiveness of three field monitoring methods. My research aims to inform the effective use of monitoring methods for wētāpunga. In chapter 3, I compared the attractiveness of peanut butter and banana lures to captively bred wētāpunga at the Auckland Zoo breeding facility. There was no difference in the number of approaches or latency to approach a lure between the peanut butter and banana treatments. In chapter 4, I compared three field monitoring methods, baited tracking tunnels, baited arboreal tunnels and visual surveys, over two nights on Ōtata Island, The Noises. Due to heavy rain and wind, both the tracking tunnels and arboreal tunnels became waterlogged and no evidence of wētāpunga presence was recorded using these two methods. However, I observed 16 wētāpunga and 15 tree wētā during visual surveys, demonstrating that visual surveys are more reliable for monitoring wētāpunga in difficult weather conditions. The results of my research suggest that non-lethal food based lures can be effective for monitoring native insects. Monitoring programmes should consider the environment, season and behaviour of target species when selecting a monitoring method.