Sugar Island is in the St. Marys River just below Sault Ste. Marie, Michigan. It is fifteen miles long and varies in width from seven miles at the northern end to about two miles at the southern end. The northern end of the island is farmed, but the narrow southern end is almost completely wooded and uninhabited except by summer visitors, who stay mainly on the shore and seldom venture inland except to travel the one county road. The island gets its name from the large amounts of maple sugar and syrup formerly produced there, and today, sugaring is still an important source of income for the inhabitants. During several periods spent on the Preserve, especially in August of 1948 and 1949 and December of 1949, four main types of small mammal habitats have been trapped: 1) mixed upland forest of spruce, balsam, white pine, and paper birch, with an understory of moosewood, mountain maple, and sugar plum; 2) nearly mature bog forest of spruce, balsam, red maple, and black ash; 3) upland rocky hillsides with an open forest of large-toothed aspen, white pine, paper birch, balsam, and spruce; 4) black spruce bog. Perhaps the most interesting feature of the Osborn Preserve is its strategic location between the Upper Peninsula-Wisconsin region and the Algoma region of Canada. The local mammals may be divided into two groups–those whose ranges encompass the Great Lakes and those whose ranges stop in this region. It is this second group that encounters the Soo region and the St. Marys River as a potential barrier, either to eastward or westward expansion.