Population density and group composition of Japanese sika deer (Cervus nippon yakushimae) in an evergreen broad-leaved forest in Yakushima, southern Japan

摘要

The population density of Japanese sika deer (Cervus nippon yakushimae Kuroda and Okada) in an evergreen broad-leaved forest in Yakushima, southern Japan, was surveyed over 4 years from 1998 to 2001. Two approximately 50 ha study sites, Hanyama and Kawahara, were established with a total of 4 km of census trails at each site. The estimated densities of sika deer at the two sites were 43-70 deer km~(-2) at Hanyama and 63-78 deer km~(-2) at Kawahara, although these values might be underestimates. The adult sex ratio (number of adult males : number of adult females) ranged from 0.6 to 1.0 at Hanyama, and from 0.4 to 0.9 at Kawahara. Mean group size was 1.9 deer (male group, 1.5 deer; female group, 1.6 deer; mixed group, 3.6 deer). The population density of sika deer was relatively high compared to other sites in Japan, with the exception of very small (<10 km~2) islands. Possible explanations for this naturally high density of sika deer in an evergreen broad-leaved forest in Yakushima are discussed.