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

Abstract

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 km2) islands. Possible explanations for this naturally high density of sika deer in an evergreen broad‐leaved forest in Yakushima are discussed.