Abstract
We are currently experiencing a sixth mass extinction, and while conservation action is urgently needed, efforts are severely hindered by significant taxonomic bias. Insects, despite being disproportionately affected by the current biodiversity crisis, receive less conservation attention. One such threatened species is the Cromwell chafer beetle, Prodontria lewisii. This species is a nocturnal, flightless beetle found only in the 81 ha Cromwell Chafer Beetle Nature Reserve (CCBNR).
Despite years of monitoring and research, aspects of this species biology and ecology are still poorly understood. In particular, we have a lack of understanding of its habitat requirements and preferences, distribution throughout the CCBNR and population dynamics, as well as a lack of effective monitoring methods. Pitfall traps, for example, are known to have poor capture rates.
To address these issues, we trialled several approaches. Pitfall traps were combined with drift barriers and bait to test if they improve catch rates. Trail cameras were tested for their ability to detect P. lewisii activity. Night-time transect counts were undertaken throughout the whole CCBNR to determine distribution and habitat use. This data was then used to conduct vegetation surveys in regions where P. lewisii were and were not observed to determine vegetation preferences. Further vegetation surveys were conducted at Mata Au Scientific Reserve, where larval P. lewisii were translocated by the Department of Conservation in November 2024. Vegetation communities were compared using non-metric multidimensional scaling.
My findings show that pitfall capture rates were improved by drift barriers but not by bait. Trail cameras successfully detected P. lewisii, but further work is required before they can be considered a reliable source for monitoring, as I had very low observation numbers. Nighttime transect counts remain the most effective method of monitoring P. lewisii. Vegetation composition within the CCBNR did not differ between regions with and without P. lewisii, but the reserve’s plant communities differed significantly from those at the translocation site. It remains unclear how P. lewisii will respond to this new habitat. Monitoring of this population will allow for further understanding of vegetation requirements.
This research provides further understanding of the habitat requirements of P. lewisii, as well as helping to develop best practice monitoring methods. This will help conservation efforts, which require accurate measures of population numbers to determine conservation status. An in-depth understanding of habitat will also improve the ability to translocate P. lewisii, helping to protect against extinction.