Should I stay or should I go? Comparison of movement patterns of a flightless bush-cricket in sparse versus dense grassland

Abstract

We investigated the movement patterns of a large-bodied flightless bush-cricket, Isophya costata, occurring in a site that had an area of mainly short sparse grasses and an adjacent area of mainly taller grass with complete cover. In each of the two types of grassland, 10 males and 10 females were released and followed for 15 days. The field data showed that the grassland type did not significantly affect the daily movement activity of females; they moved 6–7 m/day in both types of habitat. However, the daily movement of males was significantly higher (11–12 m/day) in the short grassland patches than in tall patches (6 m/day). The shape and the area of the movement patterns showed that both males and females migrated from short vegetation towards high vegetation. However, the shape of the movement pattern of high grassland is nearly circular for both sexes, which indicates that the movement is almost a random walk. In the short grassland patch, males moved over a larger distances than females, while in the area covered by tall grass, both sexes moved over the same distances. Using the average daily movements of males and females, the random walk model can describe the observed movement patterns for releases in both the short and tall grass areas.