Recommendations for non-lethal monitoring of tree weta (Hemideina spp.) using artificial galleries

Wildlife sanctuaries in Aotearoa/New Zealand involve community groups that often prefer using non-lethal monitoring methods for invertebrates. We examined one method for monitoring tree weta with the aim of improving monitoring design. Pest management at our study site did not vary for 10 years before our study and remained unchanged between sampling, so we assumed that abundance of tree weta would not vary significantly over the four years of the study. We recorded occupancy and marked every tree weta (Hemideina spp.) using the same set of 38 artificial tree-hole refuges (galleries) every 1-2 weeks. We tested the prediction that non-lethal monitoring of tree weta is a suitable proxy for relative weta abundance by comparing the number of tree weta using the same galleries four years apart. As expected, no change in numbers of weta was detected. However, the level of site/gallery fidelity, seasonal fluctuations and movement between artificial galleries suggest that monitoring design needs to incorporate the life history and behaviour of these insects. We recommend comparison of weta occupancy be restricted to the same season, galleries be placed more than 50 m apart and checked only once or twice a year.