Introduced in the days of sailing vessels, probably in the last 100-150 years, and have since become widespread and pests dwelling and agriculture crops in Papua New Guinea (Herrington, 1977; Flannery, 1995a). Before the 1970s they were found chiefly in association with humans in coastal and larger inland towns (Ryan, 1972, Taylor et al. 1982) and were reported to be more common than Norway Rats (R. norvegicus). They are now confined mainly to the lowlands (from sea-level to 750m) around human dwellings and cultivated areas (Flannery, 1995a).
Individuals from the Port Moresby area has the same chromosome number as individuals from Australia and New Zealand (Yosida et al. 1971; Yosida, 1980). It is now widely established on the New Guinean mainland as well as on a number of offshore islands. West Papua/Papua Province: the distribution of this introduced murid in western New Guinea remains poorly known, but there is documented records from Salawati, Waigeo, and possibly Batanta in the Raja Ampat Archipelago, as well as Biak-Supiori, Numfoor and Yapen (=Japen) in the Cenderawasih (Geelvink) Bay (Flannery, 1995b). Also recorded from the Fakfak on the Bomberai Peninsula (Strandtmann & Mitchell, 1963).
Papua New Guinea: apart from being well established in the Port Moresby area there is documented records from Rabaul and Ulu (=Mauke) Island in the East New Britain Province (Scrimgeour & Purohit, 1984; Flannery, 1995b), Manus Island in the Admiralty Islands (Flannery, 1995b), Lihir Island in the Lihir group of islands in New Ireland Province (Bismarck Archipelago), Emirau Island of the St Matthias Islands (Admiralty Islands) (Matisoo-Smith et. al 2009) as well as Sideia Island in the Louisiade Archipelago (Flannery, 1995b; Pages et al., 2010).
- Flannery, T.F. (1995a): Mammals of New Guinea. Cornell University Press; Revised edition.
- Flannery, T.F. (1995b): Mammals of the South-West Pacific & Moluccan Islands. Cornell University Press.
- Scrimgeour, E. M., & Purohit, R. G. (1984): Chronic pulmonary cryptococcosis in a Rattus rattus from Rabaul, Papua New Guinea. Transactions of the Royal Society of Tropical Medicine and Hygiene Volume 78 (6): 827-828.