New Zealand is home to three rat species: the ship rat (Rattus rattus) also called the common or black rat, which is the most widespread; the Norway rat (Rattus norvegicus) or brown rat, the largest; and the kiore (Rattus exulans), the smallest.
All three eat native insects like wētā, as well as snails, frogs, lizards, tuatara, birds, bats, and the flowers, fruits, and seeds of many plants.
Ship rats pose the greatest threat. Agile climbers, they easily reach tree nests and have been linked to the extinction of several native birds, including the bush wren, huia, laughing owl, New Zealand little bittern, and South Island snipe.
Norway rats have thick tails shorter than their bodies and small ears. Strong swimmers, they can cover distances of up to a kilometre in water. They mostly live on the ground and prey on eggs and chicks of ground-nesting birds like the New Zealand dotterel and shore plover, though they can climb when needed.
Kiore arrived with early Māori voyagers, while Norway and ship rats came later with whalers, explorers, and settlers. Outcompeted by these newer arrivals, kiore now survive only on a few offshore islands and in parts of remote Fiordland.
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