Effects of sika deer on forest mice in evergreen broad-leaved forests on the Tsushima Islands, Japan

抄録

The effects of sika deer Cervus nippon on two forest mice species, Apodemus speciosus and A. argenteus, were studied in evergreen broad-leaved forest on the Tsushima Islands, western Japan, in 1997. Four study areas with different deer densities were established: 1) deer-free, 2) 3.6 deer/(km)², 3) 22.8 deer/(km)², and 4) 74.9 deer/(km)². Mice were caught in snap traps; 100 traps per area (45 m × 45 m), on three consecutive nights (300 trapnights/area). The weight of leaf litter, which can be regarded as a habitat index for Apodemus species, was less in areas with higher deer densities. The density of A. speciosus tended to be inversely proportional to deer density; this trend was more obvious in the breeding season. The relationship between A. argenteus and deer density was vague or proportional. The total standing stock of both Apodemus species was lower in higher deer density areas; nevertheless, density changes of both species were inconsistent. The decrease in the standing stock of A. speciosus was not accounted for by an increase in A. argenteus. The effects of sika deer on both Apodemus species possibly operate by affecting their predators on Tsushima.