Preliminary Survey of Habitat Use bySciurus vulgaris orientisin a Natural Forest of Hokkaido Island, Japan

Abstract

The Eurasian red squirrel Sciurus vulgaris Linnaeus, 1758 is widely distributed in the northern part of Eurasian Continents, Sakhalin Island (Russia), and Hokkaido Island (Japan) (Gurnell and Wauters 1999; Wilson and Reeder 2005). The distribution area of this squirrel is widest of all the world’s squirrel species (Gurnell 1987). In Russia, this squirrel occurs in boreal coniferous forests consisting of larch (Larix), pine (Pinus), and spruce (Picea) (Lurz et al. 2005). The Hokkaido population of the Eurasian red squirrel is regarded as an endemic subspecies: S. vulgaris orientis (e.g., Imaizumi 1960). This subspecies occurs from lowlands to mountains (1,650 m) in Hokkaido (Takaragawa 1996). Ecological characteristics of S. vulgaris orientis living in forests isolated by agricultural and urban areas are reported (Lee and Fukuda 1999; Lee 2001, 2002). In urban areas, this squirrel frequently feeds cones of Pinus koraiensis (Lee 2002), which was introduced to Hokkaido by human activity (Maeda 1970; Miyaki and Miyaki 1980). In Hokkaido’s original environments, however, the ecological characteristics of S. vulgaris orientis are little known. Therefore, this subspecies should be studied in its original habitats, such as the natural and mountainous forests of Hokkaido. Vegetation of Hokkaido’s natural forests mainly contains Abies sachalinensis, Picea jezoensis, Quercus mongolica, Betula spp., and Tilia japonica (Tatewaki 1958; Horikawa 1976; Okitsu 2002). This is different from forests of northern Eurasia where S. vulgaris populations are extensive. Abies sachalinensis, which is confined to Hokkaido Island, the southern parts of Sakhalin Island, and the Kuril Islands (Satake 1989), is the most abundant conifer tree in Hokkaido’s natural forests. Unlike the coniferous forests of northern Eurasia, several kinds of hardwoods account for 60% of the trees in Hokkaido’s forests (Okitsu 2002). In this unique vegetation structure, there may be an association between S. vulgaris orientis distribution and forest type. Ognev (1966) described S. vulgaris in Russia as inhabiting coniferous forests containing spruce and pine. In south-central Sweden, this squirrel inhabits Norway spruce-dominated forests (Andren and Delin 1994). In the natural forests of Hokkaido, therefore, this subspecies should prefer coniferous forests, even though hardwoods are more dominant. Here, we present preliminary results of microhabitat use by S. vulgaris orientis in the mountainous natural forests of Hokkaido.