A possum roadkill victim in New Zealand, where the alien species virtually rates as a natural disaster. What disquieted the author, though, was that the adult female's newborn joey was still alive . . .

'Park on a possum' is far easier said than done

By Mark Brazil | Apr 4, 2002

Back in 1848, some bright spark had a “good” idea. Let’s import common brush-tailed possums from Australia and fur-farm them in New Zealand, they thought. They followed up on that idea with action — action that New Zealand’s environment has been paying for ever since.

Furs look good, feel good and some people will buy them by the bundle, or so common logic ran in the pre-wildlife conservation and pre-animal-rights era. And so that good idea worked — all too well.

New Zealand became detached from the ancient super-continent, Gondwana, around 80 million years ago. It was probably the first chunk to break away, as it did so before land mammals had evolved. As result, the islands existed for millennia in isolation and without mammals, a treasure trove of Gondwanan species, none of which had ever seen a mammal — until human colonists decided to introduce them in their hundreds.

Some of those alien species didn’t last long, but one that did is the possum trichosurus vulpecula. From those early, fur-farming days, these voracious, nocturnal vegetarians fanned out across the country. Now their territory covers an estimated 92 percent of the land area, and their numbers total an astonishing 60 million animals. That means about as many possums as sheep inhabit New Zealand.

If you have trouble imagining the impact of 60 million possums, consider this: They strip trees and other plants of about 20,000 tons of vegetation each and every night.

Possums are selective. Their preference is for certain trees that they find tasty. Having stripped these, though, they turn to other plant species. Trees in bloom are bared of their flowers, complete with nectaries, depriving them of their reproductive potential. Other favored foodstuffs are fresh shoots and leaves; these consumed, the tree is stimulated to new growth — which the possums quickly return to strip again. In this way, after merely a couple of years healthy native trees are killed — and the possums move on to the next.

It is also said that, like squirrels in other parts of the world, possums opportunistically consume birds’ eggs and young. With 60 million possums ranging the bush, they are likely to encounter a fair proportion of the country’s breeding birds. It’s no wonder that the forests are so quiet.

The fur-trade no longer exerts any controlling influence on possum numbers. Beginning in the 1970s, the killing of wild animals for their fur sparked tremendous outcry, particularly in Europe and America. Where previously a leopard-skin coat, an ocelot cape or sealskin boots may have been a fancy fashion item, the tide of public opinion turned as information came to light about the devastation of wild-animal populations and the cruel ways in which the creatures died.

The result was a downturn in the fur market. But while severely depressed wildcat populations benefited from the ban on fur trading, the emotional backlash against furs was indiscriminate and the thriving trade in possum fur from New Zealand was also checked.

Whereas it was obviously desirable to control trade in the fur of endangered wild species, in New Zealand, where the possum was causing havoc, the removal of that check on numbers enabled the population of this alien species to continue to explode.

Possums are extremely successful in New Zealand. They breed in both autumn and spring, are not faced by competition for habitat from other native mammals (as they are on their home turf in Australia), they have no significant predators and native plants have not evolved anti-mammal toxins as Eucalypts have in Australia. As a result, there are no digestive checks limiting how much vegetation possums can consume.

Adding insult to injury, possums are also a major transmitter of bovine tuberculosis and so pose a threat to the country’s multi-billion-dollar beef, dairy and venison industry. In response, the government spends in excess of $17.7 million a year trying to control possums, and that’s not including large sums spent on research and testing new control methods.

Ironically, in their homeland across the Tasman Sea the possum population is much smaller and the creatures are suffering habitat loss. In Australia animal-rescue centers care for injured or orphaned possums. It is a situation that requires us to separate our emotional responses to wild creatures. In Australia, an injured possum is deserving of help — it is, after all, a native species suffering habitat reduction at the hands of man. In New Zealand, though, “Park on a Possum” might be an appropriate slogan for drivers.

In September last year, while driving along the quiet coastal road up the northwest part of South Island, I came across a number of vehicle-casualties. A little blue (or fairy) penguin killed on the road was a sorry sight; it had been making for a nesting area inland of the road. The remaining casualties were all of the same species — the possum. Drivers, sharing the view that even one fewer possum helps the plight of the forests, make little effort to avoid them — some even do their best to add to the toll of roadkill.

But a few kilometers north of Punakaiki, in Paparoa National Park, I came across a saddening scene: another dead possum on the road. What made this an emotional experience, though, was the fact that the victim was a female — carrying a joey.

At first sight I assumed both were dead, the joey having crawled out of its dead mother’s cooling marsupium, but as I stopped to photograph it, I could see that it was moving feebly. What a dilemma.

Had I been in Australia, I would have mollycoddled the creature and taken it to a friend’s native-mammal rescue facility. But in New Zealand, I was facing a creature that is a serious ecological hazard, an immense pressure on native forests and one that the government is spending huge sums of money to eradicate.

It was an interesting experience, analyzing the interplay of my own emotions. My initial response was, “My goodness, I must do something to help.” That, I feel sure, was in part the product of my upbringing, partly natural sympathy for an injured creature — and also motivated in part by the desire to escape social comment and such labels as “cruel” and “heartless.”

But a few minutes quiet contemplation helped me put that inappropriate emotional response into perspective: 20,000 tons of vegetation lost each and every night! Trees and other native plants devastated by this alien; populations of insects and birds dependent on those plants being negatively impacted. I decided I could cope after all with being thought cruel and heartless.

I felt that in not actively killing it I wasn’t so much doing the cruel thing, as the cowardly thing. I walked away and left the joey to die. What would you have done?