Effects of habitat mosaic on home range size of the Japanese squirrel, Sciurus lis

The Japanese squirrel, Sciurus lis Temminck, is distributed on the Honshu, Shikoku, and Kyushu islands of Japan, although local extinction of this species has recently occurred in the southwestern part of Japan. To assess the impacts of environmental change on habitat availability for the Japanese squirrel, I studied spatial responses to habitat fragmentation. Suitable habitats were defined in accordance with previous work showing that the squirrels selectively use natural or secondary forests. Studies were conducted in a natural forest on Mt. Takao, western Tokyo, and in a neighboring forest fragmented by plantation development. Home range size, mean daily range size and mean daily movement distance were estimated by radio-tracking 16 female and 17 male squirrels. Home range size in both sexes and the daily range size in females increased as the percentage of suitable habitat declined. Japanese squirrels survived by expanding home ranges, even in fragmented forests including unsuitable vegetation types, as far as habitat mosaic was small.