The Common Brushtail Possum (Trichosurus vulpecula, from the Greek for "furry tailed" and the Latin for "little fox") is the largest of the Australian possums.
Like most possums, the Common Brushtail is nocturnal. It is mainly a folivore, but has been known to eat small mammals such as rats. In most Australian habitats, leaves of Eucalyptus are a significant part of the diet but rarely the sole item eaten. This is probably because of the tannins and other chemical defences present in eucalypt leaves. Around human habitations, Common Brushtails are inventive and determined foragers with a liking for fruit trees, vegetable gardens, and kitchen raids.
They are highly inquisitive and live in troupes of about a dozen individuals with a complex social structure not dissimilar from wolves and primates.
During the day, Common Brushtails sleep in a den in a hollow tree or any other convenient place, notably ceiling spaces that are not securely sealed. Although primarily arboreal and not found in places without trees to provide refuge, they spend a good deal of time on the ground. They are able to stand upright.
The very loud hissing, crackling territorial call of the male Common Brushtail has a harsh quality. They have a number of other vocalizations, mainly consisting of pitched clicks. Most are also relatively quiet. Socially they may be solitary or they may form small groups which share territory.
European settlers aiming to establish a fur industry introduced the Common Brushtail to New Zealand, where there are now about 70 million Common Brushtail Possums. Their introduction has been ecologically damaging because the native vegetation has evolved in the absence of mammalian herbivores. Possums selectively browse native vegetation causing particular damage to broadleaved trees, notably Metrosideros species including rata. This leads to competition for food with native forest birds, changes in forest composition and eventually canopy collapse. Possums are opportunists and will predate the eggs of nesting native birds. They do not have so much impact on Southern Beech (Nothofagus), but their presence tends to reduce the species diversity of Nothofagus forest since they eat many of the other species that would naturally be present. The predation of bird eggs (including Kiwi) and chicks and has led them to be referred to as "reluctant folivores" in that they eat foliage to survive but prefer other foods. Possums have also been known to push out or compete with Kiwi for their burrows to acquire a dry sleeping place.
Possums are also said to be vectors of bovine tuberculosis, which provides a major threat to the dairy, beef and deer farming industries.[4] The transmission path has yet to be discovered.
Attempts to reduce numbers by trapping and poisoning have had some success. Trapping and cyanide are generally used by individual hunters as pest control or fur harvesting, while the Department of Conservation (DoC) uses sodium monofluoroacetate (1080)to target larger areas.
To prevent damage to young trees it seems to be necessary to keep numbers very low, perhaps 5% of the levels that would be reached without interference. The possum is widely regarded in New Zealand as a major ecological threat, and some forestry industry funded ecological organisations such as the Ecologic Foundation encourage its elimination; however its impacts are compounded by those of other introduced species such as Red Deer and Goats, not to mention human activities such as agriculture, forestry, and mining. DoC is the largest single agency involved in possum control and much possum control is also carried by the AHB, councils and regional authorities, especially to combat the threat of bovine tuberculosis.
A small fur industry was developed, and possum trapping and shooting continues to the present day, and the fur is often sold as 'eco-fur' by a number of small manufacturing and retailing businesses. The numbers of animals taken for fur is insignificant in relation to the numbers killed in poisoning. Environmentalists question whether the industry is compatible with the aim of drastically reducing or eliminating possums. A number of New Zealand companies are exporting possum carcasses to Taiwan, Hong Kong and Malaysia for human consumption, where possum is known as the delicacy kiwi bear.