Indirect effects of increasing sika deer (Cervus nippon) on carabid beetles in the Tanzawa mountains

Abstract

We estimated the indirect effects of an over-abundant deer population on carabid beetles in the Tanzawa Mountains by comparing their community from five sites with different levels of damages to vegetation. We also sampled carabids from in- and outside of three 8-years-old deer exclosures to assess the effectiveness of these fences on carabid conservation. The mass of forest-floor vegetation had a negative effect on the number of the most-abundant species, Pterostichus yoritomus, and a positive one on that of the species with the largest body size, Carabus (Leptcarabus) procerulus, as was demonstrated by Poisson regression and model selection. This result was compatible with a general trend that decline of vegetation cover affects small carabids positively and large carabids negatively. A prominent effect of vegetation mass was also suggested from a redundancy analysis targeting five dominant carabid species. These results showed the strong indirect effect of over-abundant deer populations on carabid communities. Lots of C. procerulus were captured from inside deer exclosures, which had been installed before vegetation was heavily damaged, suggesting their effectiveness in the preservation of large-bodied carabids.