Diversity of dung-beetle community in declining Japanese subalpine forest caused by an increasing sika deer population

The Ohdaigahara subalpine plateau in Japan has recently suffered a reduction in primary forest land caused by an increasing population of sika deer (Cervus nippon). Deer have debarked many trees, causing dieback, gradually changing the primary forest first to light forest with a floor that is densely covered with sasa grass (Sasa nipponica) and then to S. nipponica grassland. To examine the effects of vegetative transformation on the dung-beetle community, we compared the diversity and abundance of dung-beetle assemblages in the primary forest, transition forest, and S. nipponica grassland using dung-baited pitfall traps. The species richness and species diversity (Shannon-Wiener index) were significantly highest in the primary forest and lowest in the S. nipponica grassland. The evenness (Smith-Wilson index) was highest in the primary forest and nearly equal in the transition forest and S. nipponica grassland. The abundance was apparently greater in the transition forest than in the primary forest and S. nipponica grassland. These results suggest that loss of primary forest resulting from an increasing deer population decreases the diversity of the dung-beetle community while increasing the abundance of dung beetles in the transition forest. Sika deer use transition forests and grasslands more frequently than primary forests as habitat, but an increase in dung supply there does not necessarily increase the diversity or abundance of dung-beetle assemblages.