Common Brushtail Possum (New Zealand)

The Common Brushtail Possum
Common Brushtail Possum
The Common Brushtail Possum is a nocturnal, semi-arboreal marsupial of the family Phalangeridae, it is native to Australia, and the largest of the possums.Like most possums, the Common Brushtail is nocturnal...

(Trichosurus vulpecula) is a major agricultural

Agriculture in New Zealand

Agriculture in New Zealand is the largest sector of the tradeable economy, contributing about two-thirds of exported goods in 2006-7. For the year ended March 2002, agricultural exports were valued at over $14.8 billion...

and conservation

Conservation in New Zealand

Conservation in New Zealand has a history associated with both Māori and Europeans. Both groups of people caused a loss of species and both amended their behaviour after realising their effect on indigenous flora and fauna.-Protected areas:...

pest in New Zealand. It also goes by the name Paihamu.

Introduction by European settlers

European settlers aiming to establish a wild source for food and fibre and fur pelts for clothing introduced

Introduced species

An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...

the Common Brushtail Possum

Common Brushtail Possum

The Common Brushtail Possum is a nocturnal, semi-arboreal marsupial of the family Phalangeridae, it is native to Australia, and the largest of the possums.Like most possums, the Common Brushtail is nocturnal...

from Australia to New Zealand. In 2009, the New Zealand population was estimated to be 30 million.

Agriculture

Possums are vectors of bovine tuberculosis, which is a major threat to the dairy, beef and deer farming

Venison

Venison is the meat of a game animal, especially a deer but also other animals such as antelope, wild boar, etc.-Etymology:The word derives from the Latin vēnor...

industries. The disease is endemic in possums across approximately 38 per cent of New Zealand (known as ‘vector risk areas’). In these areas, nearly 70 per cent of new herd infections can be traced back to possums or ferrets. The Biosecurity Act 1993

Biosecurity Act 1993

Biosecurity Act 1993 is an Act of Parliament in New Zealand passed in order to prevent pests and other unwanted organisms. It was a world first.Part 5 of the Act provides for a National Pest Management Strategy and Regional Pest Management Strategy....

, which established a National Pest Management Strategy, is the legislation behind control of the disease in New Zealand. The Animal Health Board

Animal Health Board (New Zealand)

The Animal Health Board commonly known by its acronym, AHB, is an incorporated society, legally responsible for managing and implementing the National Pest Management Strategy for bovine tuberculosis in New Zealand. Its powers derive from the Biosecurity Act 1993 and its mission is to eradicate...

(AHB) operates a nationwide programme of cattle testing and possum control with the goal of eradicating M. bovis from wild vector species across 2.5 million hectares – or one quarter – of New Zealand’s at-risk areas by 2026 and, eventually, eradicating the disease entirely.

The TBfree New Zealand programme is regarded as "world-leading". It has successfully reduced cattle and deer herd infection rates from more than 1700 in 1994 to fewer than 100 herds in July 2011. Much of this success can be attributed to sustained possum control reducing cross-infection and breaking the disease cycle. For example, at Hohotaka, in New Zealand's central North Island

North Island

The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...

, control work from 1988 to 1994 achieved a sustained mean reduction of 87.5% in the density of Tb‐infected possums. As expected, annual Tb incidence in local cattle herds consequently declined by a similar amount (83.4%).

Possums are controlled through a combination of trapping

Trapping

Trapping may refer to:* Animal trapping, the remote capture of animals* Trapping , a fighting technique and range* Trap , a color management technique* Mantrap, a security device...

, ground-baiting and, where other methods are impractical, aerial treament with 1080 poison.

From 1979–1984, possum control was stopped due to lack of funding. In spite of regular and frequent TB testing of cattle herds, the number of infected herds snowballed and continued to increase until 1994. The area of New Zealand where there were TB wild animals expanded from about 10 to 40 per cent.

That possums are such effective transmitters of TB appears to be facilitated by their behaviour once they succumb to the disease. Terminally ill TB possums will show increasingly erratic behaviour, such as venturing out during the daytime to get enough food to eat, and seeking out buildings in which to keep warm. As a consequence they may wander on to paddocks, where they naturally attract the attention of inquisitive cattle and deer. This behaviour has been captured on video.

Conservation

The introduction of possums has been ecologically damaging because the native vegetation has evolved in the absence of mammalian omnivore

Omnivore

Omnivores are species that eat both plants and animals as their primary food source...

s. Possums selectively browse native vegetation causing particular damage to broadleaved trees, notably Metrosideros
Metrosideros
Metrosideros is a genus of approximately 50 trees, shrubs, and vines native to the islands of the Pacific Ocean, from the Philippines to New Zealand and including the Bonin Islands, Polynesia, and Melanesia, with an anomalous outlier in South Africa. Most of the tree forms are small, but some are...

species including rata
Metrosideros robusta
Northern rātā , is a huge forest tree endemic to New Zealand. It grows up to 25 m or taller, and usually begins its life as a hemiepiphyte high in the branches of a mature forest tree; over centuries the young tree sends descending and girdling roots down and around the trunk of its host,...

. This leads to competition for food with native forest birds, changes in forest composition and eventually canopy collapse. Possums are opportunists and will eat the eggs of native birds. They do not have so much impact on Southern Beech (Nothofagus

Nothofagus

Nothofagus, also known as the southern beeches, is a genus of 35 species of trees and shrubs native to the temperate oceanic to tropical Southern Hemisphere in southern South America and Australasia...

), 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 and chicks has led them to be referred to as "reluctant folivores" in that they eat foliage to survive but prefer other foods.

Control

Attempts to reduce numbers by trapping and poisoning have had some success. Trapping and cyanide

Cyanide

A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

are generally used by individual hunters as pest control or fur harvesting, while the Department of Conservation

New Zealand Department of Conservation

The Department of Conservation , commonly known by its acronym, "DOC", is the state sector organisation which deals with the conservation of New Zealand’s natural and historic heritage...

, Animal Health Board

Animal Health Board (New Zealand)

and Regional Councils use biodegradable 1080 poison to target larger areas. Studies by DoC have found that the risk of the few losses of native birds; (34 individuals in 70 aerial drop operations) and native invertebrates and mammals are outweighed by the recovery of the native species once the competition for food and predation has been eased. There is the added benefit of killing other invasive species

Invasive species in New Zealand

A number of introduced species, some of which have become invasive species, have been added to New Zealand's native flora and fauna.Both deliberate and accidental introductions have been made from the time of the first human settlement with several waves of Polynesian people at some time before the...

. There have been isolated reports of pets, in particular dogs, succumbing to poisoning from 1080, probably through eating possum carcasses. The Animal Health Board

Animal Health Board (New Zealand)

and the Department of Conservation jointly operate poison drops. The effects of these drops on the environment have been considered by ERMA

Environmental Risk Management Authority

The Environmental Risk Management Authority is a New Zealand government agency which controls the introduction of hazardous substances and new organisms....

in allowing the use of 1080. and in consultation with Māori. There is opposition against the use of 1080 from some quarters since New Zealand is now the world's largest consumer of 1080.

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. 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.

In 2009, it was announced that conservation measures had achieved some significant success, especially in certain regions, and had reduced possum numbers to around 30 million animals from a carrying capacity of 48 million. (Estimates produced in the 1980s of 70 million possums were flawed.) Almost half (13.3 million hectares) of New Zealand's vegetated land is under some form of possum control, either for conservation reasons, or to reduce the spread of bovine tuberculosis.

Economic uses

A small cottage industry in fur pelts and wool mixed with possum fur fibre has developed, and trappers and hunters provide the raw material. 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 rising and has almost equalled the numbers killed in poisoning. A number of New Zealand companies are exporting possum carcasses to Taiwan, Hong Kong and Malaysia for human consumption, where possum is regarded as a delicacy and known as "Kiwi bear". There is also a small industry processing possum meat as 'Possyum' dog food, also for export. In an example of "coals to Newcastle", NZ Biosecurity has a regulation governing the import of frozen possum meat from Australia for human consumption.

External links

Possum information at the Department of Conservation
Possum information at the Ministry of Agriculture and Forestry
Ministry of Agriculture and Forestry (New Zealand)
The Ministry of Agriculture and Forestry is the state sector organisation of New Zealand which deals with matters relating to agriculture, forestry and biosecurity...
Possum information sheets and manuals at Landcare Research
TB free New Zealand – TB control programme in New Zealand
Bovine TB information on Department of Conservation website – The use of 1080 for pest control in New Zealand – Possums as reservoirs of bovine tuberculosis
Information about bovine TB on 1080: The Facts website – Facts about how 1080 poison is used to control bovine TB in New Zealand

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Introduction by European settlers

Agriculture

Conservation

Control

Economic uses

See also

Further reading

External links