This checklist includes all thirty-five mammals known to exist within the boundaries of Apostle Islands National Lakeshore. Most of these are present on the islands with exception to those that hibernate. Most probably crossed over on the ice, thus excluding the hibernators. Naturally, there are exceptions.
Black bear are large enough to survive a long swim in the cold waters of Lake Superior.
They can and do travel freely among the islands. Raccoons have been released as pets on Madeline Island. Even skunks have been introduced there. Star-nosed moles occasionally wander out of their winter burrows and have somehow reached some of the islands. Bats are the only other mammals that hibernate and are found among the islands.