Norway rats may have first arrived in Alaska with Vitus Bering. Rat Island in the Aleutians was named by 1790, so rats must have arrived earlier (Murie, 1959). Haas (1986) examined specimens from Anchorage, Fairbanks, and Nome. Murie (1959) reports Norway rats from Atka, Kiska, and the Rat Islands. Peterson (1967) reports "Rattus" from Unalaska.

Brechbill (1977) mentions the possibility of black rats, Rattus rattus, in the Aleutians, but there are apparently no specimens and it is difficult to imagine them persisting with Norway rats in a cold treeless environment.

Species diagnosis

• Molar teeth with tubercles or cusps arranged in 3 longitudinal series
• Basal length of skull more than 50mm
• M1 longer than the combined lengths of M2 and M3

Literature cited

• Brechbill, R. A., 1977. Status of the Norway rat. In: M. L. Merrit and R. G. Fuller, The Environment of Amchitka Island, Alaska. Technical Information Center, Energy and Development Administration.
• Haas, G. E., N. Wilson, H. D. Brighton, 1986. Observations on Norway rats, Rattus norvegicus, in Kodiak, Alaska. Canadian Field-Naturalist, 100(3):383-385.
• Murie, O. J., 1959. Fauna of the Aleutian Islands and Alaska Peninsula. U.S. Fish and Wildlife Service, North American Fauna No. 61.
• Peterson, R. S., 1967. The land mammals of Unalaska Island: present status and zoogeograpy. Journal of Mammalogy, 48:119-129.