From Sport to Pest - The Challenge of Introduced Species by Carter

                                                      An invasive species: the stoat

In the beginning of European settlement in New Zealand in the 19th century, settlers brought an array of mammals for agricultural purposes as well as sport and food. In doing so, many of these species brought from overseas have brought drastic issues upon the native fauna here in New Zealand. Agricultural animals such as cattle and pigs have been managed for quite some time by farmers. Their domestication has limited many of their damaging impacts.

Some of the wild species of rabbits, possums, stoats/ferrets, and deer have left native plant and animal populations in a muddle. Rabbits have been a huge ecological challenge for over a century. They were originally introduced for sport and food, but quickly resulted in damage to alpine grasslands, saplings, orchards, and gardens, and are concerning competitors for grazing sheep. The rabbit population took off in the 1870’s, where over the next few decades the displacement for sheep and loss of vegetation heavily outweighed the revenue New Zealand was bringing in from rabbit skin and meat. In 1945, over 20 million rabbits were killed and ate as much food as over 2 million sheep. With legislation, night-shooting and poisoning have been sought as the best techniques to handle rapid rabbit populations.

Like rabbits, possums also became an issue to native plants. Introduced primarily for skin trade, it became quite clear the damages outweighed the revenue. In 1947, all protection among the possums was removed and in 1951 a bounty system was introduced. At present, the bounty system is discontinued and is entrusted in part of rabbit legislation through shootings and poisonings. Another pest that was introduced have been stoats/ferrets. They are carnivores, and by nature, natural predators. As we are quite familiar with the famous flightless New Zealand native bird, the kiwi, populations of the kiwi are in grave danger due to these introduced predators. They are accountable for half of kiwi chick deaths and are known to eat kiwi eggs as well. They are killing kiwis at the root, making it near impossible for kiwi populations to bounce back. DOC 250 traps are a primary use for stoat/ferret killings.

An additional pest includes many species of deer. With no large predators, populations grew out of control. Introduced for sport, they were protected until the 1920’s. By the 1930’s, restrictions were dropped and deer were now classified as noxious animals. Over the next few decades of killings, deer were eventually domesticated for farming in 1969. This information was important in our lectures in establishing the context of New Zealand history. Additionally, these had been topics addressed by numerous farmers on our farm visits. Through conservation efforts and continuous action against invasive species, I believe it is possible to restore populations of native species and limit/eradicate non-native species.