The Ecology of Rattus exulans ( Peale ) Reviewed

Several aspects of the ecology of Rattus exufans are revie:ved in an effort to collate a large proportion of the widely scattered hterature relatillg. to the species. Subspecific relationships are discuss~d to illustrate the early. Co~fu~lOn. regarding taxonomic position. Literature covenng R. exula~s.geog~aphicdistnb~tlOn, habitat, nutrition, reproduction, movements, and competltlon With other specIes of Rattus, is reviewed and discussed. Rattus exulans probably ranks third in the genus for extent of geographic range and is of interest from both academic and economic viewpoints. The species occurs on nearly every Pacific island that lies within 30 degrees of the equator and has extended its range south to include New Zealand. It is thought to have spread in association with Polynesian colonization. Ofparticular interest is the species' secondary modification of range and habitats as a result of com~etition with other members of the genus, partlcularly Rattus rattus (Linnaeus) and Rattus norvegicus (Berkenhout). The Polynesia~ r~t causes da~­ age of considerable economIC Importance .ill some areas of the Pacific and Southeast ASIa, primarily to coconuts, sugarcane, and rice. It is also an important vector of the typhuscarrying mite and of the plague flea in some areas (Audy and Harrison, 1951; Elbel and Thaineua, 1957). This review attempts, within the limits of available literature, to collate data concerning the past and present ecology of the species:.The literature of R. exulans relevant to Hawall has been well reviewed by Tomich (1969: 36 and 124) but an assembly of other literature seems in order. Few studies have been devoted to the Polynesian rat alone, most having been made in conjunction with investigations of other members of the genus; some have been a part of studies which were specifically aimed at rodent control. It is hoped that the collation of a section of the data relevant to the species will be of use to other workers in the field. I Manuscript received 14 June 1972. 2 Department of Agriculture, Koronivia Research Station, Nausori, Fiji. SUBSPECIFIC RELATIONSHIPS At least five names have been assigned to Pacific island rats as they were successively discovered on widely separated small islands. They are, Musexulans Peale (1848), Tahiti; Mus vitiensis Peale (1848), Fiji; Mus maorium Hutton (1877), New Zealand; Musjessook Jentink(1879), New Hebrides; and Mus huegeli Thomas (1880), Fiji. All these species are considered to be synonymous with Rattus exulans (Peale), by Tate (1935), but he considered Rattus hawaiiensis Stone (1917) and Rattus micronesiensis Tokuda (1933) to be distinct species. More recent authors (Ellerman, 1947; Marples, 1955; and Johnson, 1962) considered the latter two species to be of subspecific or race rank. Ellerman (1947) listed 12 races of R. exulans including exulans, concolor, browni, ephippum, aemuli, negrinus, surdus, todtgensis, vulcani, stragulum, raveni, and hawaiiensis. Johnson (1962) considered R. micronesiensis to be a subspecies of R. exulans. The present review will follow the opinions of Ellerman, Marples, and Johnson by includ~ ing all races and subspecies mentioned as members of the species R. exulans. GEOGRAPHIC DISTRIBUTION R. exulans has a wide geographic range, but within the range distribution is disjunct. The dispersal of the species east of Indonesia is thought to have been in association with human dispersal (Tate, 1935), though the suggestion that rats were deliberately conveyed is discounted by Shapiro (cited in Tate, 1935, as a personal communication). It is believed that