Overview
The only terrestrial mammals native to New Zealand were three species of bat. One of these Mystacina robusta only recently became extinct, while two species still maintain a precarious existence. The extinct mystacine was not known from the main islands during historic times, but survived until the late 20th Century on small islands off Stewart Island where it finally succumbed in the late 1960's after rats were accidentally introduced. Today, 28 species of introduced terrestrial mammals have existing, established wild populations.
Man and his animal introductions are part of the natural environment. No matter how much we regret alteration, New Zealand's primeval environment is gone. When man arrived in New Zealand he precipitated an ecological revolution from which we are only now beginning to emerge with a changed and more resilient fauna and flora. Today the explosive waves of introduced animals penetrating an undisturbed environment are becoming more restricted and confined to a few remote areas of southern Fiordland. The introduced animal populations are beginning to stabilise naturally and as a result of intensive management techniques, supported in some instances by new market demands and in others by improved control mechanisms. Economics now largely determine the effectiveness of control, and improved techniques now make it possible to remove some species entirely from isolated offshore islands or mainland sanctuaries.
Of all animal introductions, man has had by far the greatest impact and is implicated either directly, or indirectly in all extinctions of native animals and plants since c.1000 AD, firstly through the destruction of habitat by fire and axe, and later by flooding, drainage, and through the use of machines and chemicals; the inadvertent and deliberate introduction mammalian predators and grazers, and the deliberate hunting of species already endangered by habitat destruction.
An estimated four hectares of habitat are destroyed everyday in New Zealand. Extensive clearing of native vegetation has left less than 25% of the original cover (only 7% of lowland forest remains) compared with over 80% in some industrailised countries such as Japan. During the Polynesian period of settlement, two mammals and one food plant were introduced – 32 species of bird are known to have become extinct and forest clearance was extensive. The European period of settlement has seen the introduction of 130 species of bird (33 survive), 51 species of mammal (28 survive), about 30 species of fish (23 survive), 40 species of worms, 60 spiders & mites, 12 slugs & snails, 1100 insects and 1700 plants. A further four species of bird and one fish have become extinct, while many others are endangered and only persist in small numbers on offshore islands.
The total number of extinctions of native animals other than birds and fish will never be known, but includes insects, snails, reptiles and amphibians. In recent years the importation of animals has continued for zoological gardens and exotic farming ventures. While few of these animals may escape to establish wild populations, the risk is always present. For example, chinchillas are permitted in the North Island, however, they are banned from the South Island where they potentially could cause a disaster if they escaped into the southern mountains. The extent to which man has influenced the distribution of animals can be seen on a global scale. Size has never been a limiting factor: the elephant, largest of the living land mammals was first imported to New Zealand in the latter part of the 19th Century.
Removal of "noxious" species today must be done with care: the introduced parma wallaby was almost eradicated from Kawau Island before it was realised that the animals were possibly the sole surviving representatives of that species and some animals were saved for re-introduction to their native Australian habitat. Some feral animals display advantageous characteristics – feral cattle, apparently resistant to footrot, survived on Enderby Island in the Auckland Islands for 100 years before being eradicated by conservationists, however, one cow survived the eradication attempt and was later captured and transported to an Agricultural Research facility where it is hoped it will provide future genetic stock for cross breeding with other domestic cattle. Feral populations of many species, particularly deer, pigs, chamois and thar, as well as trout, are important economically as they form the basis of the recreational and tourism hunting and fishing industries.