New Zealand Pests – Possums

You wouldn’t think such a cute-looking animal would want to harm anyone, would you? Well, think again. At least here in New Zealand, the possum is Public Enemy Number One!

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The common brushtail possum (Trichosurus vulpecula) was initially introduced into New Zealand from Australia in 1837 in an attempt by European settlers to establish a wild source of food and a fur trade. That’s right—to eat them and to make clothing out of possum skins.

Possums continued to be actively brought into New Zealand up until 1921. And the possums liked it here. They liked it a lot here. They liked it here too much.

The problem was that there were no natural predators in New Zealand to keep the possum population in check. And the second problem was that possums are voracious eaters primarily of plant life, and they were destroying huge swaths of the natural vegetation in the country. At perhaps the peak of the possum problem in the 1980’s there were 60-70 million possums in New Zealand, that is, almost 18 possums for every man, woman and child in the country! Lots of possum.

Possums take over New Zealand (1)

Possums take over New Zealand (1)

But first, let’s take a closer look at this public enemy which is found everywhere on mainland New Zealand including on Stewart Island in the south.

The possum is a marsupial (babies raised in a pouch like kangaroos). They weigh 2-5 kg and are about the size of a cat. They have a pointed face with bulging black eyes, big ears and a bushy tail. Long claws enable possums to be good tree climbers. They live for about nine years and females have one baby a year. As a quick aside, possums in the United States are generally called opossoms and are a different species.

Possums are nocturnal. They are omnivores but primarily eat plant life. They are particularly fond of the new shoots of plants, the growing part, and commonly return to the same tree night after night devouring so much of the growth that the plant dies or becomes susceptible to disease.

Possums also eat the stems, fruits, seeds, bark and flowers of plants, and to a lesser degree bird eggs, chicks and insects—everything—which leads to further strain on fragile ecosystems.

Possums can devastate forests in a New Zealand, including killing off huge stands of the more beautiful trees such as rata and pohukatawa, reducing a forest to shrub land.

flat,550x550,075,fAs you remember, New Zealand grew up or evolved as an island separate from any other bodies of lands for MILLIONS of years. It has its own unique ecosystems that include the lack of natural predators which might limit the possum’s numbers. And plants that might have evolved or developed defenses against the possum never had to. In an evolutionary sense, it never occurred to them. Hence, when the possum showed up, not only was it uncontested by any natural predators but plants were ill equipped to survive its ravages.

If there was a possum heaven, it was New Zealand.

By comparison, many of the plants in Australia where the possum originated, have characteristics such as thorns to protect them from possums. Also, there are a variety of natural predators that keep the possum population in check. Indeed, just to show you the difference that 900 miles of Tasman Sea can make, the possum in Australia is a protected species!

So how much do the possums in New Zealand eat? First, the good news— the possum numbers are down to about 35 million, only about eight per person. Each year the possums in New Zealand eat almost 4.5 million tons of vegetation. That number doesn’t mean much to me so I found a children’s website that equates the amount possums in New Zealand eat to 110 million hamburgers per night. Wow, now that’s a lot!

If all this wasn’t enough, possums are also the main wildlife reservoir of bovine tuberculosis (Tb) which affects cattle and deer. New Zealand’s dairy industry is its largest and main export business so this is obviously of major concern.

Tb is endemic in possums across about 38% of New Zealand; in these areas, nearly 70% of new herd infections in dairy can be traced back to possums or ferrets. Tb is transmitted by physical contact. Often after the possum becomes sick and dies from Tb, an animal such as a cow licks or sniffs the carcass infecting the animal and spreading the disease.

In 1946 possums were declared a pest in New Zealand and since that time, there has been a war on possums.

800px-1080PoisonWarning_gobeirneCurrently the control (killing) techniques used include hunting, trapping and poisoning often done by the Department of Conservation (DoC) in New Zealand. Poisons include cyanide and sodium fluoroacetate, or compound 1080 as it is called. The poison is either placed in bait traps or dropped from the air. These techniques have been successful where they have been used extensively.

What happened to the possum fur industry which started all this? Possum fur was an export business during most of the 1900’s but has dropped off in recent decades. Today, possum fur is commonly combined with blends of merino wool to produce clothing. It is marketed under such names as Ecopossum, Merinosilk, Merinomink, possumdown, eco fur or possum wool. Possum fur fibers are noted for being hollow which supposedly makes the fur both warm and light weight.

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But being a pest, possums don’t have much standing in New Zealand society. Possum hunts are apparently relatively common events and some are even sponsored by schools to raise money.

No, we don't have bake sales—but how about a Possum and Pig Hunt!

However, in 2010 a bit of controversy developed when the New Zealand SPCA criticized a number of schools for having “possum-tossing contests” which involved throwing dead possums. Apparently this was going a bit too far although the principal of one of the schools argued that it helped the pupils engage with the outdoors adding that the children were well supervised.

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The public argued back, “If it starts out with possums, it’s soon going to be cats . . .”

“If it starts out with possums, it’s soon going to be cats…”

Surprisingly, at least in one poll, 60% of the people thought it was okay.

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2 thoughts on “New Zealand Pests – Possums

  1. But they are so cute…not at all like the North American opossum. Apparently Captain Cook’s botanist, Sir Joseph Banks, named it possum because it looked like the North American Opossum. The site goes on to say that it’s a good thing he didn’t travel too far north, or the crocs would be called alligators. Hmmm. Well, I’m glad to hear that their fur has superior thermal properties as I bought two sets of them as gifts for friends back in Colorado who can apparently use them as “nipple warmers.” I didn’t realize there was a calling for that sort of thing.

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