Captain James Cook and later whalers and sealers introduced cats (Felis catus), but these did not become common until the 1830s. In the 1870s, rabbit numbers were driving farmers from their land, so quantities of cats were released to control them.

Ferrets are known as fitch in the fur trade industry. They are called polecats in Europe where they originated and the Maori name for the ferret is Torihura.

The possum found in New Zealand is the Australian brushtailed possum, while Possums are found in North America where they are called opossums.

Ship rats (Rattus rattus) are one of the most widespread mammals in NZ “one of the most successful mammalian weed species”. Yet they are rarely seen because they are nocturnal, arboreal and shy.

Stoats were first introduced to the South Island in 1884 to control rabbits. A number of further liberations in other areas of the country soon followed. Stoats spread quickly into the forests of Fiordland and other areas where there were no rabbits. They are now found from Northland to Bluff.

Weasels were introduced in 1885, when 67 of them were released on a peninsula by Lake Wanaka. Initially they were abundant, but during the first half of this century their range and numbers dropped. By the 1950s, the weasel had become rare.