The Santa Rosa beach mouse (Peromyscus polionotus leucocephalus) occurs on a single barrier island in northwest Florida, but its distribution on the island is poorly known. In 1991-92 we searched for mouse tracks at 1-km intervals along the 78-ktn island and set traps at 23 locations. Beach mice occurred in beach and interior dune habitats across most (96%) of the undeveloped stretches (57 km) of the island. Beach mice were significantly less common in areas developed for residential or commercial use and tracks were found along just 7 of 21 km of developed land. We captured only 3 house mice (Mus musculus), all near buildings. Tracks of house cats (Felis catus) were significantly more common in developed areas. Predation by cats has likely reduced or eliminated beach mouse populations along developed beaches and at the undeveloped east end of the island. Habitat loss and house cats in 3 developed areas have apparently separated the beach mouse population into 4 isolated units. Conservation efforts should focus on maintaining existing habitat, controlling free-ranging house cats, and assessing the need for translocating mice among habitat fragments.
