Kiore or Pacific rats (Rattus exulans) are found throughout Asia and the Pacific. They are believed to have originated in South-East Asia, and dispersed through the Pacific in the canoes of Polynesian seafarers. The Polynesian ancestors of Māori arrived in New Zealand around the 13th century with kiore on board.
Appearance and names
Kiore are small for a rat – about 11–13 centimetres long excluding the tail, and 60–80 grams in weight. They are brown, with a grey-and-white underside.
Kiore is the usual name given to this species in New Zealand, although other names have also been used: maunga-rua is a ‘large rat’; tāpapa a ‘well-grown rat’; torokaha a ‘big buck’; toko-roa a ‘light-coloured rat’; while hāmua refers to a rat considered an ill omen that was seldom eaten.
Habitat and diet
During the day, kiore stay in holes in the ground or in hollow tree trunks, emerging at night to feed. Māori trapped kiore in winter, when the rats were in prime condition – in summer they were thin. When kiore fattened and their fur changed colour, it indicated plentiful forest berries and the approach of spring. Hīnau berries were their favourite food, as signalled in the proverb, ‘Mā wai e kai te hīnau, te kame a te kiore’ (for whom is the hīnau, it is food for the kiore). They were also known to eat miro, tawa, tawai, karamū, taraire, kohekohe, pūriri and patatē berries. The tāwhara fruit of the kiekie plant was another favourite. It was common to tie kiekie leaves over the fruit to stop kiore eating it before it could be harvested.
Kiore also ate the eggs and chicks of birds, as well as lizards, frogs and insects. They contributed to the extinction of a number of species.
Norway rats (Rattus norvegicus) were introduced by Europeans in the 18th century, and ship rats (Rattus rattus) in the 19th century. Māori names for these rats included pou-o-Hawaiki and muritai. Their introduction, together with that of the mouse, led to a decline in kiore numbers because of competition for resources. By the early 1920s kiore were considered extinct. However, some survive in Fiordland, on Stewart Island and on several offshore islands.
Rats in research
Kiore might be small, but they loom large in scientific research. Ancient Polynesian voyages have been traced by analysing the DNA of kiore from different Polynesian islands. In New Zealand, carbon dating of the bones of kiore, and the seeds and snail shells kiore gnawed, tells us that Māori ancestors arrived around the 13th century.
A northern tribe, Ngātiwai, sees itself as kaitiaki (guardian) of kiore. Ngātiwai and a number of Māori believe there are historic and cultural reasons these rats should survive. However, kiore are not protected by law, and evidence of their predation on endangered native birds, lizards and insects have seen them eradicated from Crown-owned islands by the Department of Conservation. The department recognises that kiore may be of cultural interest, and consult with tribes before carrying out eradication programmes.