Alien Possums Gobbling New Zealand Forests, Birds

Sean Markey in Wellington, New Zealand
for National Geographic News
April 25, 2006

With its bushy tail, tall ears, and pink nose, Australia's brush-tailed possum could be the poster child for cute critters.

But here in New Zealand—where millions of the animals eat native plants, trees, and birds by the bushel—the marsupials are possums non grata.

"They are gobbling through this country as if it was made of ice cream," said Herb Christophers, spokesperson for the New Zealand Department of Conservation (DOC) in Wellington.

The pests were introduced to New Zealand in the 19th century and today spread bovine tuberculosis to livestock and wreak havoc on forests, competing with native birds for food.

Possums can munch half a pound (300 grams) of foliage a day and prey on the eggs and chicks of endangered birds like the kokako, kereru, and kiwi—New Zealand's iconic national bird.

"They're an absolute pest," said Anne Field, a Christchurch weaver who uses yarn spun from merino wool and dead possum fur.

"I don't think anybody has a good word for them."

Evolutionary Isolation

Native to Australia, where they are now protected, brush-tailed possums were first introduced to New Zealand in 1837 to jump-start the fur trade.

The cat-size marsupials gained a permanent foothold here by 1858. Finding abundant food and no natural predators, they have never looked back.

Today possums occupy nearly 99 percent of the country, according to Christophers, and are poised to "take a stranglehold" on the last possum-free scrap of land in New Zealand, the area of Fiordland.

New Zealand's environment is defenseless against invasive animals like possums, stoats, and rats, because it evolved in isolation over the last 65 million years.

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