In 1837, New Zealand fur promoters released Australian possums to build a new industry; the first attempt failed, so settlers kept trying until the animals invaded the country

In 1837, New Zealand settlers brought Australian possums across the Tasman Sea. They wanted to start a fur trade. The plan failed immediately. Instead of giving up, settlers kept trying for decades until possums became one of New Zealand’s most damaging invasive species.

According to the New Zealand Department of Conservation, the common brushtail possum is endemic to Australia. Settlers first introduced it to New Zealand in 1837 to establish a fur trade. That first release failed. A second release in 1858, at the same Southland location, finally succeeded. Many people confuse this animal with the opossum, a separate genus Didelphis species native to the Americas that has never been present in New Zealand. The brushtail possum has a thick, bushy tail, dense fur, a pointed snout, and large ears. It comes in two colors, grey and black, with variations within each.

Settlers kept trying after the first failure
One failed release could have ended the story there. It didn't. According to the New Zealand Department of Conservation, the 1858 Southland release was the one that finally succeeded, and possums spread from there across most of New Zealand. Possums thrive in places with shelter and a steady food supply. They reach especially high densities in podocarp broadleaf forests. They also do well where forest meets pasture, and these areas now support some of the country's densest possum populations.

Possums were once protected, not culled
For decades after their 1858 establishment, brushtail possums were a protected fur resource in New Zealand, with regulated hunting seasons designed to preserve their numbers for the fur trade. According to Te Ara Encyclopedia of New Zealand, that protection was formally removed in 1946, once officials concluded the ecological damage outweighed the value of the fur industry. The Waikato Regional Council similarly notes that protection was lifted around this time, citing 1947, after which possums were reclassified as pests and coordinated control efforts began in earnest.

Why this animal became a national threat
Possums have few natural predators in New Zealand, which helps them spread. DOC says possums are abundant, and even predators such as feral cats do little to control their numbers.

The damage extends to wildlife, forests, and farming. Leaves make up most of a possum's diet, but possums are opportunistic omnivores. They eat native birds and eggs, native land snails such as Powelliphanta, invertebrates including weta, and plant material such as buds, flowers, fruit, and nectar, thereby competing with native birds and reptiles for food. When possums strip a plant, they can disrupt its growth. Possums prefer certain native trees, including rata and kamahi, and those species suffer the heaviest damage. Possums also use tree hollows that native birds such as kākāriki and saddlebacks need for nesting.

Possums also affect farming, especially dairy and deer farms. Dairy and deer farmers face the added risk of possums spreading bovine tuberculosis. DOC says the combined cost of possum damage and control efforts is in the tens of millions of dollars. Researchers using nest cameras in South Westland have documented possums and stoats preying on kea inside their nests. This illustrates the threat possums pose to New Zealand's native wildlife.

Control efforts today rely heavily on aerial and ground-based distribution of sodium fluoroacetate, commonly known as 1080 poison, alongside trapping and ground-based hunting. The use of 1080 remains one of New Zealand's most debated conservation tools; supporters point to its effectiveness at reducing possum densities across large, rugged tracts of forest that would otherwise be inaccessible, while critics raise concerns about non-target species and land safety. Despite the controversy, it remains a key part of New Zealand's strategy for protecting native ecosystems from possums and other introduced predators.

New Zealand is still paying for this decision
Controlling possum numbers requires coordinated effort. DOC works with agencies including OSPRI, regional councils, and the Ministry for Primary Industries. DOC directs resources toward possum control at priority sites to protect native species and the ecosystems that depend on them. This work supports the country's Predator Free 2050 goal, which depends on public participation in predator control alongside government agencies.

A fur-trade plan that began in the 19th century ultimately succeeded, but at a steep cost. Nearly two centuries later, New Zealand’s forests, native birds, and farmers are still dealing with the consequences.