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Top 10 Invasive Species Found in New Zealand

Updated: Aug 7, 2021

New Zealand has been known for having no natural predators. At least this was like that before the humans settled. It was populated by Polynesians around 700 years ago. Then it was colonized by Europeans who brought new culture, language, and social order.

With the Europeans came some of the nastiest pests. They were brought in the hopes to establish better trades. In this article, I will tell you more about these nastiest pests, what they are, and what damage they cause.

New Zealand Magpie

Australian magpies are robust birds, 37 to 43 cm in length. They are very sedentary and territorial. They can be very aggressive at protecting their nests and competing for food. Not every other native species can confront a magpie. That is why magpies are viewed as New Zealand's invasive species.

Over 1000 Australian magpies were introduced into New Zealand from 1864 to 1874. They are treated as pest species by many regional and local councils. They are thought to displace other native species of New Zealand.

A Magpie
A Magpie


Rats are known for their destructive eating habits throughout the world. In New Zealand, it is no exception. The so-called Ship rats and Norway rats are two major pests that were introduced by Europeans. The other species is called Kiore. It is known for having a cultural and spiritual significance to Maori people.

All three species pose a threat to native plants, bird eggs, flowers, birds, seeds, lizards, and frogs. Their eating habits make them strong competitors in finding and securing food sources. Rats are good climbers and can climb up a tree to prey on nests. They also eat large flightless invertebrates such as snails and weta.

The image displays the following rats in sequence from left to right: the Ship rat, Norway rat, and Kiore rat.

Argentine Ants

Argentine ants pose a serious threat to New Zealand's biodiversity. They are found in urban and natural areas.

Ants are very aggressive and territorial. Their unique attribute is the ability to cooperate. They can connect many colonies forming a huge network of ant workers. Their increased appetite makes them even more dangerous to local trees, flowers, and plants.

They are also major household and garden pests, usually found in warm, dry soil. They kill native invertebrates that otherwise would feed native species. They can threaten endangered populations by eating lizards, bird eggs, and hatched chicks. During Spring and Summer, they prefer to feed on nectar and honeydew.

Because of their diverse diet, they displace indigenous populations of Kiwi. They also compete with nectar-eating birds such as Tui and Bellbirds. They also tend to eat lizards, skinks and geckos, and other native invertebrates.


The common brushtail possum is the greatest threat to New Zealand's natural environment. Its size and teeth make it one of the most destructive pests in New Zealand. It was introduced from Australia in 1837 to establish a fur trade. The first release was unsuccessful. But the second release, which was made in 1857, 20 years after, was successful.

The threat posed by possums is their omnivorous and herbivorous diet. They tend to eat carrion, bark, crops, eggs, plants, leaves, and everything of nature origin. Their only predator - the feral cat, is much smaller in size so it does not hunt down possums in large enough numbers to guarantee good control measures for possum population size.

The plenty of food that possums can eat in New Zealand makes them reproduce very fast. As of today, around 30 million possums are inhibiting the native lands of New Zealand. This has massive implications on native flora and fauna.

Besides the mentioned destructive dietary habits, possums are also carriers of several diseases. Most problematic of which is Bovine Tuberculosis. BV, for short, affects cattle and causes trouble to farmers.

Feral Cat

A feral cat looks like an ordinary one except it lives in the wild. It also does not rely on humans for the provision of food and shelter. In contrast to stray cats, wildlife feral cats are completely separated from humans. They have their needs provided by themselves.

European explorers brought the first cats to New Zealand in 1769. Those cats helped control the number of rats aboard more than 50 years after cats were introduced to New Zealand. A feral cat population was established and was expanding around the country.

Feral cats have a major impact on native and non-native species. They are considered invasive predators. They prey on birds, rabbits, bats, lizards, mice, and insects.

Feral cats prefer to live near coastal areas and riverbeds. This makes their predation impact skink populations in these places.

On offshore islands, cats feed on forest and sea birds, which has major consequences as well.

Their habitats usually consist of forest areas, farmland, riverbeds, and coastal areas. So if you go out for a bushwalk, be prepared to meet a feral cat in the wild!


Rabbits are a significant agricultural and economical threat. European rabbits were among the first mammalian animals introduced to New Zealand. They were distributed throughout drier regions of the mainland and many offshore islands. They populate those environments at an extreme pace resulting in large numbers of them.

Domestic rabbits were carried on sailing ships as potential food. They were imported in the 1860s to establish the domestic fur and meat trade. Increased farming, later on, assisted their growth in numbers. By the 1880s rabbits became a serious threat to the fragile New Zealand economy.

Rabbits are agricultural pests. They compete with livestock for pasture, consuming the grass and vegetation on land. They also destroy native plants and flowers by browsing.

Invasive Plants