The following domestic animals became wild at one time or another: dogs, cats, goats, cattle, sheep, horses, and pigs. Polynesian dogs reached New Zealand with the Maori Great Migration in A.D. 1350 but became extinct with white settlement; feral European dogs were later common in some areas, but have since been exterminated.
Feral cats are probably the descendants of those left by sealers and whalers early in the settlement of New Zealand. At a later stage the spread of rabbits from the early seventies onwards was accompanied by an increase of wild cats, which appear to be more numerous where rabbits are plentiful. At present feral cats are found throughout the country, both in forested areas and on farmlands of the North and South Islands and on some of the outlying islands, including Little Barrier and Kermadec Islands. The value of feral cats in controlling rabbits and rodents is probably outweighed by the effect they have had on some native birds: such rare birds as the Stephen Island wren or the Chatham Island fernbird are reputed to have been exterminated by them. On Little Barrier Island, however, a fairly constant relationship has been established between cats and their main prey – petrels in spring, and kiore or native rats throughout the year. Cats seem to have had little effect on the native-bird population of that island. There is no organised control of wild cats in New Zealand, but a number are destroyed by the wildlife rangers of national parks, reserves, and acclimatisation societies.
The first goats were put ashore by Captain Cook, and since then they have been repeatedly liberated on various islands for emergency food or kept on marginal farming country to control noxious weeds (mainly blackberry). Some of these animals have escaped into the forests, become feral and built up into large populations in both islands. Some goats are kept in a semi-domestic state, but most are truly wild. Goats eat all palatable plants and can live in varied environments. They can change the original vegetation completely, thus causing depletion of soils and accelerated erosion. On Three Kings and on Cuvier Island, goats were long established and induced a completely new goat-proof flora; they have now been exterminated there. Control of wild goats was begun in 1932 by the Department of Internal Affairs, but in 1956 the duties were taken over by the New Zealand Forest Service. The total of 332,121 goats destroyed by official shooters between 1951 and 1958 illustrates the huge job of control.
Feral cattle, horses, and sheep have a similar origin. Most of these are the progeny of stock in marginal farming areas that were inadequately fenced or subsequently abandoned. A few feral cattle are still reported in forests in remote parts of the North Island and in the north-eastern and north-western parts of the South Island. Few feral horses are still to be found in openings in the exotic forests on the Central Plateau of the North Island. There are many more small bands of feral sheep, found mainly in the high country of the South Island; 15,687 of these animals were destroyed by official hunters alone in “critical” areas between 1951 and 1958.
Pigs were liberated by Captain Cook and, later, by sealers and early settlers, both to supply the Maoris with a new domestic animal and to provide stranded voyagers with food on outlying islands. By 1840 feral pigs were well established throughout the main islands and on several outlying islands. The distribution of feral pigs is limited by the existing supply of food and cover; pigs are more numerous in the North Island than in the South. Since their liberation pigs have had a considerable effect on plant and animal life. With feral goats and cattle they have often played an important part in rain-forest degradation and its replacement by a new plant community. Pigs are claimed to have destroyed tuatara and ground-nesting birds (such as kakapos) and petrels on outlying islands. In marginal farming districts they kill lambs and cast sheep. Wild pigs give sport to some hunters and also establish seedbeds for trees in dense strands of fern. They are listed as noxious animals and are controlled mainly by private shooters under a bounty scheme or by poisoning. Between 1951 and 1958, 212,382 pigs were “officially” killed.
by Kazimierz Antoni Wodzicki, B.AGR.SC., M.SC.(N.Z.), PH.D.(CRACOW), Director, Animal Ecology Division, Department of Scientific and Industrial Research, Lower Hutt.
- Tutira, Guthrie-Smith, H. (1963 ed.)
- The Naturalisation of Animals and Plants in New Zealand, Thomson, G. M. (1922)
- Introduced Mammals of New Zealand, Wodzicki, K. A. (1950).