Abstract
Dung beetles are useful indicators of habitat quality in tropical regions. When we evaluate habitat quality with using baited traps that attract insects for a distance, traps need to be placed to limit immigration of insects from outside the study area. To determine the minimum distance from a forest edge into grassland needed to limit immigration of forest dung beetle species, we set baited pitfall traps on transects of 100, 200, and 300 m into grassland from the edge of an Acacia mangium plantation with a small secondary forest in East Kalimantan. Additionally, to evaluate the availability of riparian reserves of trees along the margins of grasslands as habitat for forest species, we placed traps in a riparian reserve next to the grassland. Since the species found to be most abundant in the plantation were not collected in the grassland, we suggested that 100 m buffer zone should be sufficient to limit the unwanted capture of forest beetles in baited grassland traps. Moreover, since the species that were abundant in the plantation were also abundant in the riparian reserve, we argued that riparian reserves in grasslands might act as a habitat patch for forest species. Since distance from both forest edge and riparian reserve did not relate to the result of the ordination of species composition at each trapping location in the grassland, these distances did not generally affect the communities of dung beetles in the grassland.
