Effects of mowing on Isophya costata, Natura 2000 species (Orthoptera), by direct mortality and management history

We studied the impacts of mowing on an isolated Isophya costata population at a fine scale on a study area of 5 ha established in Balaton Uplands (Hungary). Of the examined hayfield sites, 1 hectare was ploughed one season five years ago. In 2021, similar to 27% of the continual hayfield and 18% of the formerly ploughed grassland were unmowed. The size of the local population (similar to 1,700 specimens) was similarly calculated based on the measured density and the mark-release-recapture method data. According to our results, collected in 200 5 x 5 m quadrats in 2022, a magnitude difference in the mean density per quadrats was observed between sites mowed (M) and unmowed (UM) in the previous year and between sites ploughed five years ago (RG) and not (HF)(HFUM: 1.95 +/- 0.21, HFM: 0.23 +/- 0.05, RGUM: 0.88 +/- 0.14, RGM: 0.09 +/- 0.03). Further, we show that mowing the hayfields in an economically optimal time causes significant (min. 40%) damage (mostly lethal) to Isophya costata individuals. Due to the high incidence of females at the end of May and beginning of June, the detected mortality can significantly reduce the success of egg laying, and thus the development of the following generation. However, mowing on hayfields is essential for maintaining habitat structure optimal to Isophya costata and against the ecological succession and dispersion of invasive plant species. Specific conservation measures can dissolve the above contradiction.

Automated summary

This study investigated the effects of mowing on an isolated population of Isophya costata in Balaton Uplands, Hungary. The results showed that while mowing hayfields is important for maintaining optimal habitat structure for Isophya costata, it also causes significant damage to the individuals.