Habitat diversity and peat moss cover drive the occurrence probability of the threatened ground beetle Carabus menetriesi (Coleoptera: Carabidae) in a Bavarian mire

Within the Natura 2000 network, there is a legal imperative to protect endangered species. A lack of knowledge about habitat requirements for these species undermines the ability to make informed decisions about appropriate conservation measures, especially for isolated populations that may have developed habitat preferences specific to their region. Carabus menetriesi is an endangered ground beetle found in Europe and warrants protection under EU law. We collected occupancy data of C. menetriesi using live pitfall traps over two seasons in 2016 and 2018 at a protected nature reserve in southern Bavaria, Germany. Here, we present the results of a patch-occupancy modeling approach to determine habitat preferences for C. menetriesi at this site. Our model shows that increasing Sphagnum cover and habitat diversity led to higher occupancy levels for C. menetriesi at this site, while tree cover was negatively correlated with occupancy, but increased the detectability of the species. Implications for insect conservation Measures for protecting the C. menetriesi population at the study site were taken in accordance with our results. Areas with high tree cover were thinned at several sites, although the success of this measure has yet to be determined. Our findings about habitat diversity suggest that expansion of low intensity grazing in the area, a measure that was suggested as a result of our survey and is currently in process of implementation, might benefit the species. Whether our results can be transferred to C. menetriesi populations in different habitats remains to be investigated, however, our methodological approach with regard to both the data collection and analysis can be used to assess other populations and provide important information about relevant habitat parameters for that population. This will allow conservation managers to make well-informed decisions about conserving C. menetriesi, or indeed other similar carabid species with isolated populations.

Automated summary

This article explores the habitat preferences of C. menetriesi, finding that increasing Sphagnum cover and habitat diversity can lead to higher occupancy levels for the species at the study site, while tree cover is negatively correlated with occupancy but increases detectability. Based on the results, measures for protecting the population of C. menetriesi have been implemented, and the expansion of low intensity grazing is suggested as a potential benefit to the species. The methodological approach used for data collection and analysis can be applied to assess other populations and provide valuable information about relevant habitat parameters.