Movement patterns and survival of a climate-sensitive bush-cricket species under different habitat conditions

Isophya costata is an endemic, flightless, postglacial-steppe relict of the Carpathian Basin, a Natura 2000 taxon in the European Union, and is listed on the IUCN Red List with a declining population trend. Given its mesophilic nature and habitat requirements for dense, tall vegetation, the species is highly endangered by overheating and the vertical and horizontal simplification of grasslands caused by climate change within its range . According to our research hypothesis, our focal species exhibits increased movement in response to varying effects of habitat, population, and weather. We collected data on four populations exposed to different circumstances, including optimal, suboptimal, and non-optimal habitats, as well as relocated and non-relocated specimens under various weather conditions. We observed 120 individuals over 10 days. Global Positioning System was used to record field recaptures, and movement patterns were determined using reference points and Federal Communications Commission distance calculations. Relationships between variables were analyzed using t-tests and Generalized Linear Models. In the activity of the focal species, habitat structure seemed to be the primary driver. Dispersal patterns showed that the species occupied smaller territories in optimal habitat mosaics than in suboptimal or nonoptimal ones. Analysis of movement patterns showed that individuals began moving according to a biased random walk in both suboptimal and nonoptimal habitats. However, in habitats where the grassland structure met their requirements, the individuals slowed down. In optimal habitats where the species occurs at high densities, individuals could shift their behaviour to a neighbour-avoiding random walk. At maximum daily temperatures of 30 °C we detected high disappearance rates, probably because of mortality caused by overheating. Based on these results, it can be assumed that mesophilic species seem to be highly vulnerable to global climate change in their current habitats.