Effects of Forest Cutting on Two Carabus Species: Evidence for Competition for Food

I investigated the effects of forest clear—cutting on two predatory beetles. Carabus limbatus was numerically dominant in the forest, but its density was significantly reduced on the clear—cut. C. sylvosus density was little affected by forest cutting. An enclosure experiment was conducted in order to distinguish between the effects of habitat and density on the foraging success of C. limbatus. Individual beetle mass served as an operational measure of foraging success. On the clear—cut, the foraging success of C. limbatus was subject to opposing pressures. Lower density of conspecifics tended to improve foraging success, while other attributes of the clear—cut tended to reduce foraging success. C. sylvosus is similar to C. limbatus in habitat, diet, and temporal activity pattern. C. sylvosus foraged significantly more successfully on the clear—cut, where C. limbatus was less abundant, than in the forest. I hypothesized that Carabus species compete for limiting food in the undisturbed forest, and that clear—cutting ameliorates competition by reducing the numerically dominant C. limbatus.