A creature of two worlds - the brush tailed possum - cheeky, yet deadly!

My latest feature in Wildlife Australia magazine, about the possum

seen as delightful and cheeky in Australia,

grilled as a deadly havoc-spreading menace in Aotearoa / New Zealand

There’s a well-known Aussie species, with a benign influence here, but lethal consequences once brought into Aotearoa New Zealand, even if for all the ‘right reasons’ . Henricus Peters shares the story of the brush-tailed possum…

The Australian context

The brush-tailed possum, Trichosurus vulpecula, is the most widely distributed possum in Australia. It can be found in forests, woodlands and heath all along the east coast as well as inland areas with tree-lined rivers and creeks.

The brush-tailed possum may be mis-named as an opossum, Didelphis sp., which is an American animal.

Possums – the full story

There are 27 species of possums and gliders in Australia, including 2 species of cuscus.

Possums are small marsupials that are found across Australia. They can range in size from the size of a mouse like the tiny Western Pygmy Possum (Cercartetus concinnus) at just 15 grams up to the size of a cat. The most often seen possums in backyards and urban areas are the common brushtail possum (Trichosurus vulpecula) and the Common Ringtail Possum (Pseudocheirus peregrinus). Brush-tail possums get their name from their dark, thick, bushy tail. They are about the size of a cat with pointed ears. They can vary in colour from a copper colour in northern Queensland to a grey or even blackish in the southern states.

Common Ringtail Possums are smaller than their brush-tail cousins and get their name from their long, tapering tail. The last third of their tail is white. It is prehensile, meaning it can grip like another hand.

Possums are closely related to gliders.

The Mountain pygmy possum is found above 1400m in the alpine regions of Kosciuszko National Park. It can hibernate for up to seven months of the year under the snow.

Possums live in the trees and occasionally come down to the ground to look for food. Brush-tails live in tree hollows and Common Ringtail Possums in the south of Australia build a nest out of sticks. Both kinds of possum may live in our roof if they can’t find suitable homes in trees

Possums live in territories and mark the boundaries with smells. They rub the scent from glands under their chin, chest and base of tail against trees so everybody knows who’s the boss in the area. Possums protect their territories by fighting off intruders.

The body of a possum is made for life in the trees. They have strong, sharp claws, and hand-like back feet. The Ringtail Possum has a prehensile tail which acts like another hand to help it grip tree branches with ease. They can also use it to carry nesting material.

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The brushtail possum is probably the best known of the possums in cities because it has adapted to urban living and often comes into contact with people.

The possum is nocturnal and, during the day, retreats to a hollow log, branch, tree trunk or any dark area, even inside house roofs.

Distribution

Common brushtail possums are found in Queensland, New South Wales, Victoria, South Australia, Tasmania, Western Australia and Northern Territory. They are also found in New Zealand.

It’s the last line where life becomes problematic…

Diet

In the wild, the common brushtail possum’s diet consists of leaves, blossoms and fruits, but in suburbia it will eat almost anything.

Another topic of concern….

Brushtail possums come out after dark to feed on flowers, fruit, buds and leaves of native plants. Mistletoe, one of their snacks, is a parasite that can kill gum trees, the common brushtail possum helps to protect gum trees by controlling the mistletoe.

Insects, eggs and meat may also be eaten infrequently. In suburban areas the species may become an opportunistic feeder eating almost anything that it can find. They spend their days in a den in a hollow dead branch, tree trunk, fallen log or even on the ground.

Communication

The Common Brushtail Possum is a social animal and remains in contact with its group through sounds and scents. At times, particularly during the breeding season, it makes piercing screeches in the middle of the night to establish territories and warn of danger.

Predators

The Common Brushtail Possum’s main predators include Dingoes, pythons, foxes and cats.

Wildlife Victoria advises: “Do not feed possums. Human food can be dangerous to possums and cause serious dietary imbalance.”

For many Victorians, sharing your property with possums is a fact of life. The trees and gardens around our houses provide a
modified woodland similar to their natural habitat.

Possums have adapted well to living with humans and are commonly encountered in urban areas, suburban backyards, campgrounds and sometimes the ceilings of houses.

Possums living within buildings – in Victoria

Possums are protected under the Wildlife Act 1975. Possums must not be harmed in any way or kept without approval from DELWP.

It is illegal to harass or interfere with possums. However, common brushtail possums living within buildings, municipal parks and municipal gardens may be controlled.

The trapping of common brushtail possums living in buildings is permitted for the purpose of releasing them on the same property or taking them to a registered vet for euthanasia.

Common ringtail possums generally do not live in buildings or cause damage to municipal parks. It is illegal to trap a ringtail possum without a permit.

A Governor-in-Council order was put in place to permit the trapping of common brushtail possums living in buildings for the purpose of releasing them on the same property or taking them to a registered vet for euthanasia. Trapping is a highly stressful experience for possums. The following conditions, limitations and restrictions apply in respect of trapping brushtail possums living within buildings:

Who can trap common brushtail possums ?

Home-owners or occupiers and members of their families
Building managers or their staff
DELWP licensed Wildlife Controllers

The New Zealand experience

The common brushtail possum was introduced to New Zealand in the 1830s where …. it has now become a pest species.

In Australia, it is a protected species.

Why in New Zealand?

According to historical records Department of Conservation records, the common brushtail possum was first introduced to New Zealand from Australia in 1837 to establish a fur trade. Ironically, this first release was unsuccessful and a second release in 1858 at the same Southland location was required for them to establish.

Distribution

They are now widespread across most of New Zealand. The main habitat is forest, and possum densities can be particularly high in podocarp-broadleaf forests. Margins where forest meets pasture are also popular habitat and support very dense populations.

Diet …. threats

Possums have a significant impact on many of New Zealand’s natural ecosystems. They occur in high numbers and their own predators, such as feral cats, do not have much effect on controlling possum population size.

Leaves are the main part of their diet, but possums are opportunistic omnivores, and eat native birds and their eggs, land snails such as Powelliphanta and as invertebrates including weta. They eat buds, flowers, fruit/berries and nectar, which means they compete with native birds and reptiles for food sources. The growth and life-cycle of a tree or plant is significantly affected when all parts of it are eaten. Possums also have ‘favourites’ such as rātā or kamahi trees, leading to an even greater impact on these species.

Possums often occupy holes in tree trunks for their nests which would otherwise be used by nesting birds such as kākāriki and saddlebacks.

Dairy and deer farmers have the added worry of possums spreading likely bovine tuberculosis. The value of economic loss in primary production for damage and control of possums is in the tens of millions.

Evidence shows stoats and possums alongside other animals such as stoats are eating kea, the highly unique New Zealand mountain parrot. Researchers using nest-cameras have witnessed the gruesome reality inside defenceless kea nests invaded by stoats and possums in South Westland.

Introducing the threat called possum….

Possums were first introduced in 1837 because some early European settlers were hoping to establish a fur industry. Those animals did not survive, but people kept trying. The first possum population to survive was in Southland in 1858.

In 1921 the Government made it illegal to bring any more possums into New Zealand. It was too late; by then, they were already spread across the country.

In 1946, possums were officially declared a pest in the New Zealand environment. By 1950 they were found in over half of New Zealand and they kept spreading.

Fiordland and Northland were the last areas of mainland New Zealand to be invaded by possums. In the 1960s there were hardly any possums in Northland, but by the 1990s – only 30 years later – 10-15 million were estimated to live there.

Possums numbers reached their highest point in the 1980s when there were 50-70 million of them in New Zealand. With such high populations, trappers began to make a good living from hunting them. Throughout the 1970s, prices for their skins were good. In 1981, the best year for trappers, 3.2 million skins were exported.

What do we know about their behaviour?

Kiwi Coast has some useful information about possum behaviour:

They are nocturnal and feed at night.
Often follow the same track, forming flattened paths about 20cm wide.
Have an average home range of 200m in forest and multiple nest sites.
Have favourite trees that are visited regularly, leaving extensive scratch marks in their bark and heavy browsing of leaves and fruit.
Their dislike of wet weather makes control much more successful during fine weather.

What impact do possums have?

People used to think that possums only ate plants, but in 1993 possums were filmed eating the eggs and chicks of endangered kōkako. They have since been filmed eating the eggs, chicks and even adults of many other native birds including kererū, kiwi, harrier hawk, fantail, muttonbird, and tūī. They also eat the nectar and berries that native birds like to eat so there is less food for the birds.

Possums also carry a disease called bovine Tb (tuberculosis) which they spread to cattle. They also eat pasture so there is less food for farm animals. The damage done by possums costs NZ farmers about $35 million every year. According to Te Ara website, the New Zealand Government spends over $110 million per year on possum control.