http://www.botany.hawaii.edu/faculty/duffy/arb/193-205/198.pdf

At the time of the POBSP visit, cats (Felis domestica), dogs
(Canis familiaris), and pigs (Sus scrofa) were being raised by the natives. Comments in Ward (1967) and by Lamont (1867) suggest that the pigs may have been introduced to Tongareva in 1853 from the ship wrecked vessel Chatham. Rats (Rattus sp.) were numerous in 1965, but as no specimens were collected their identity is unknown. Lamont (1867) stated that in 1853 "... [the natives] had never seen an animal larger than a very small rat, that lives principally in the cocoa-nut trees " Lamont's description suggests that the rats on Tongareva are Rattus elegans, a species widely distributed on the Pacific Islands.