Figure 1. Locations of study sites in Japan. (a) Sites more than 1 km from human habitat where no Rattus rats were detected; (b) sites where brown rat (Rattus norvegicus) was detected more than 1 km from human settlements; (c) records of brown rat far from human settlements made by earlier surveys (Ota 1968; Abe et al. 1971; Maekawa et al. 2002); (d) sites where brown rat was detected in natural habitats but less than 1 km from human settlements, (e) sites where Asian house rat (R. tanezumi) was detected more than 1 km from human settlements within its possible native range. 1 – Kiritappu Marsh, 2 – Kushiro Marsh, 3 – Daisetsuzan National Park, 4 – Torii Pass, 5 – Kasuga Primaeval Forest, 6 – Hokigamine Forest Park, 7 – Bogatsuru Marsh, 8 – Bonotsu area, 9 – Aso Bay Park. Omitted are records of Asian house rat from the Ogasawara Islands and central and southern Ryukyu Islands, where it is known to be non-native.