千葉県南部におけるニホンリス(Sciurus lis)の生息状況の変遷

概要

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This study reports on the distributional changes of the Japanese squirrel, Sciurus lis, in the southern part of Chiba Prefecture, investigated during the years 2009–2011. The investigated areas correspond to those surveyed in 2001–2003 (previous survey) with a minimum survey unit of 1×1 km grid-square. The presence of the squirrel was confirmed mainly based on bite marks on pine cones. The occurrence of the animal has been recorded in 36 of 57 sites (63 percent) which were investigated in the previous survey, but newly recorded from 15 sites. In the previous study, declines of squirrels in the northern part was emphasized, but also, in this report we show a similar status in the south. In the previous study, pine forest area decreased in the north and this could be a factor for the decline of species. On the other hand, although the southern part has much forested area compared with the north and the continuity is also maintained, the decline of pine forest has been advancing longer than in the north. It is necessary to clarify the ecology of the squirrel in the southern part, in which there are few pine forests and evergreen broad-leaved tree forest dominates.