The diversity of upland and marine habitats provides good nesting and feeding opportunities for a number of bird species. A few species of terrestrial mammals, including exotic species, have occured throughout the islands, such as cottontail rabbits, raccoons, skunks, gray squirrels, mice, muskrats, voles, and Norway rats. Some species have been known to devastate populations of small vertebrates and nesting birds. Although formal surveys are in initial stages, Eastern garter snake, Northern brown snake, and Eastern smooth green snake are known to occur on the islands.