Common brushtail possum in New Zealand

Image:Brush tail possum 4-colour corr.jpg]]

The common brushtail possum (Trichosurus vulpecula) was introduced from Australia to New Zealand, where it has become invasive and a major agricultural and conservation pest. (In Māori it is called paihamu, a transliteration of "possum".){{cite web |title=paihamu |url=https://maoridictionary.co.nz/search?idiom=&phrase=&proverb=&loan=&histLoanWords=&keywords=paihamu |website=Maori Dictionary |access-date=4 April 2019}}

Introduction by European settlers

File:NZ possum spread 1870 - 1990.jpg

European settlers aiming to establish a wild source for food and fibre and fur pelts for clothing introduced the common brushtail possum from Australia (from Victorian and Tasmanian populations){{Cite journal |last1=Pattabiraman |first1=Nimeshika |last2=Morgan-Richards |first2=Mary |last3=Powlesland |first3=Ralph |last4=Trewick |first4=Steven A. |date=2022 |title=Unrestricted gene flow between two subspecies of translocated brushtail possums (Trichosurus vulpecula) in Aotearoa New Zealand |journal=Biological Invasions |language=en |volume=24 |issue=1 |pages=247–260 |doi=10.1007/s10530-021-02635-z |s2cid=244233163 |issn=1573-1464|doi-access=free }} to New Zealand in the 1850s. Even as late as 1936 the government refused Taranaki Acclimatisation Society permission to introduce a new strain of possums{{Cite web|date=22 Jun 1936|title=NEWS OF THE DAY. AUCKLAND STAR|url=https://paperspast.natlib.govt.nz/newspapers/AS19360622.2.42|access-date=2020-11-09|website=paperspast.natlib.govt.nz}} and in 1937 the Waitaki Acclimatisation Society proposed a closed season to allow numbers to recover.{{Cite web|date=15 Oct 1937|title='POSSUM TRAPPERS. HOKITIKA GUARDIAN|url=https://paperspast.natlib.govt.nz/newspapers/HOG19371015.2.56|access-date=2020-11-10|website=paperspast.natlib.govt.nz}} The earliest introduction may have been at Riverton / Aparima in 1840. An article in Nature in 1870 warned of the dangers, as did farmers and fruit growers, but some academics supported introduction and the Department of Tourist and Health Resorts was still introducing possums at Rotorua in the 1910s. Introductions peaked in the 1920s.{{Cite web|last=L. T. Pracy|first=A. L. Poole, Director-General of Forests|date=1962|title=INTRODUCTION AND LIBERATION OF THE OPOSSUM|url=https://scion.contentdm.oclc.org/digital/collection/p20044coll6/id/625/|url-status=live|access-date=2022-01-12|website=scion.contentdm.oclc.org|archive-url=https://web.archive.org/web/20220113093041/https://scion.contentdm.oclc.org/digital/collection/p20044coll6/id/625/ |archive-date=13 January 2022 }}

By the 1980s the peak population had reached an estimated 60–70 million.Montague, T.L. (2000): [http://www.mwpress.co.nz/store/viewItem.asp?idProduct=147 The Brushtail Possum: Biology, Impact and Management of an Introduced Marsupial] {{webarchive|url=https://web.archive.org/web/20130504013256/http://www.mwpress.co.nz/store/viewItem.asp?idProduct=147 |date=4 May 2013 }}. Manaaki Whenua Press. Accessed 8 June 2013. Through control measures, by 2009 the New Zealand population had been reduced to an estimated 30 million.{{cite web

|url=http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10611804

|title=NZ possum population halved since 1980s

|date=26 November 2009

|author=NZPA

|work=The New Zealand Herald

|access-date=8 June 2013

|archive-url=https://web.archive.org/web/20121021185325/http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10611804

|archive-date=21 October 2012

|url-status=dead}}

Impacts

=Agriculture=

Possums are vectors of bovine tuberculosis (Mycobacterium bovis), which is a major threat to the dairy, beef, and deer-farming industries.{{cite web

|url=http://www.doc.govt.nz/publications/conservation/threats-and-impacts/animal-pests/the-use-of-1080-for-pest-control/3-why-we-use-1080-for-pest-control/3_1-possums-as-reservoirs-of-bovine-tuberculosis/

|title=3.1 Possums as reservoirs of bovine tuberculosis

|author=DOC

|date=July 2004

|work=The use of 1080 for pest control

|publisher=Department of Conservation

|access-date=18 December 2012

|archive-url=https://web.archive.org/web/20121219003654/http://www.doc.govt.nz/publications/conservation/threats-and-impacts/animal-pests/the-use-of-1080-for-pest-control/3-why-we-use-1080-for-pest-control/3_1-possums-as-reservoirs-of-bovine-tuberculosis/

|archive-date=19 December 2012

|url-status=dead

}} The disease is endemic in possums across about 38% of New Zealand, known as "vector risk areas", where nearly 70% of new herd infections can be traced back to possums or ferrets. The Biosecurity Act 1993, which established a national pest-management strategy, is the legislation behind control of the disease in New Zealand. The Animal Health Board 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.{{cite web |url=http://www.ahb.org.nz/Default.aspx?tabid=116 |title=What is TB? |website=Ahb.org.nz |access-date=2017-04-25 |archive-url=https://web.archive.org/web/20110130005817/http://www.ahb.org.nz/Default.aspx?tabid=116 |archive-date=30 January 2011 |url-status=dead }}

The TB-free New Zealand programme is regarded as "world-leading".{{cite web | title = Bovine TB control: What are other countries doing? | date = 21 July 2011 | url = http://www.fwi.co.uk/Articles/2011/07/19/127893/Bovine-TB-control-what-are-other-countries-doing.htm}} 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, 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%).{{cite journal | last = Kean | first = J.M. |author2=Barlow, N. D. |author3=Hickling, G.J. | title = Evaluating potential sources of bovine tuberculosis infection in a New Zealand cattle herd | journal=New Zealand Journal of Agricultural Research. | year = 1999 | volume = 42 | pages = 101–106 | doi = 10.1080/00288233.1999.9513358}}

Possums are controlled through a combination of trapping, ground-baiting (laying poisoned baits by hand), and where other methods are impractical, aerial treatment with sodium fluoroacetate, a biodegradable poison also known as 1080.{{cite web

|url = http://www.doc.govt.nz/publications/conservation/threats-and-impacts/animal-pests/the-use-of-1080-for-pest-control/1-introduction/

|title=1. Introduction

|author=DOC

|date=July 2004

|work=The use of 1080 for pest control

|publisher=Department of Conservation

|access-date = 18 December 2012

}}

File:Possum predated Powelliphanta traversi DOC 1994.jpg

From 1979 to 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.{{cite web |url=http://www.ourfuture.net.nz/Stories/180 |title=OurFuture - Future freedom from bovine TB |access-date=2012-01-13 |url-status=dead |archive-url=https://web.archive.org/web/20120330224233/http://www.ourfuture.net.nz/Stories/180 |archive-date=30 March 2012}} The area of New Zealand where TB-infected wild animals occurred expanded from about 10 to 40%.

That possums are such effective transmitters of TB appears to be facilitated by their behaviour once they catch the disease.{{cite thesis |last= Paterson|first=Brent Maynard |date=November 1993 |title= Behavioural patterns of possums and cattle which may facilitate the transmission of tuberculosis

|type= MSc|chapter= 4

|publisher= Department of Veterinary Clinical Science, Massey University, Wellington, NZ|docket= |oclc= |chapter-url=http://www.albanyrecreation.ac.nz/massey/fms/Colleges/College%20of%20Sciences/Epicenter/docs/brentpaterson.pdf |access-date=11 June 2021}} This behaviour has been captured on video.{{cite web | title = Dr Paul Livingstone letter to the editor | work = Gisborne Herald | date = 26 May 2011 | url = http://www.gisborneherald.co.nz/article/?id=22957 | access-date = 19 August 2011 | archive-url = https://web.archive.org/web/20110927185445/http://www.gisborneherald.co.nz/article/?id=22957 | archive-date = 27 September 2011 | url-status = dead }}

=Conservation=

File:Brushtail possum close up.jpg

The introduction of possums has been ecologically damaging because the native vegetation has evolved in the absence of mammalian omnivores. Possums selectively browse native vegetation, causing particular damage to broadleaved trees, notably Metrosideros species, including rātā. This leads to competition for food with native forest birds, changes in forest composition, and eventually canopy collapse. Possums are opportunists and eat the eggs of 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 and chicks has led them to be referred to as "reluctant folivores" in that they eat foliage to survive, but prefer other foods.{{cite web

|url= http://www.doc.govt.nz/publications/conservation/threats-and-impacts/animal-pests/the-use-of-1080-for-pest-control/3-why-we-use-1080-for-pest-control/3_4-possum-impacts-on-native-animals/

|title=3.4 Possum impacts on native animals

|author=DOC

|date=July 2004

|work=The use of 1080 for pest control

|publisher=Department of Conservation

|access-date=10 July 2011

}}

Control

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), Animal Health Board (AHB), and regional councils use 1080, which can have damaging effects on the surrounding ecosystem{{cite web

|url=http://www.doc.govt.nz/publications/conservation/threats-and-impacts/animal-pests/the-use-of-1080-for-pest-control/3-why-we-use-1080-for-pest-control/

|title=3. Why we use 1080 for pest control

|author=DOC

|date=July 2004

|work=The use of 1080 for pest control

|publisher=Department of Conservation

|access-date=18 December 2012}} 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. Isolated reports of pets, in particular dogs, succumbing to poisoning from 1080 have been given, probably through eating possum carcasses. The AHB{{cite web

|url=http://www.ahb.org.nz/Default.aspx?tabid=180

|title=1080 Information

|year=2009

|access-date=10 July 2011

|publisher=Animal Health Board

|archive-url=https://web.archive.org/web/20111008044533/http://www.ahb.org.nz/Default.aspx?tabid=180

|archive-date=8 October 2011

|url-status=dead

}} and the DoCjointly operate poison drops. The effects of these drops on the environment have been considered by ERMA in allowing the use of 1080.{{cite web

|url=http://www.doc.govt.nz/publications/conservation/threats-and-impacts/animal-pests/the-use-of-1080-for-pest-control/2-the-reassessment-process/

|title=2.The reassessment process The use of 1080 for pest control

|author=DOC

|date=July 2004

|work=The use of 1080 for pest control

|publisher=Department of Conservation

|access-date=21 July 2010 }} and in consultation with Māori.{{cite web |url=http://www.nzfsa.govt.nz/consumers/chemicals-toxins-additives/1080/index.htm |title=1080 |access-date=2009-04-17 |url-status=dead |archive-url=https://web.archive.org/web/20080630025716/http://www.nzfsa.govt.nz/consumers/chemicals-toxins-additives/1080/index.htm |archive-date=30 June 2008}} There is opposition to the use of 1080 from some quarters, as New Zealand is the world's largest user of 1080.{{cite web |last= Beasley |first= Michael |title= Guidelines for the safe use of sodium fluoroacetate (1080) |publisher=New Zealand Occupational Safety & Health Service |date= August 2002 |url= http://osh.govt.nz/order/catalogue/pdf/1080guidelines.pdf |accessdate=17 December 2007 |archiveurl= https://web.archive.org/web/20130209163543/http://osh.govt.nz/order/catalogue/pdf/1080guidelines.pdf |archivedate=9 February 2013}}

To prevent damage to young trees, keeping numbers very low seems necessary, perhaps 5% of the levels that would be reached without interference. DoC is the largest single agency involved in possum control, but much of which is also carried by the AHB, councils and regional authorities, especially to combat the threat of bovine tuberculosis.

In 2009, 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.{{cite web|url=http://www.landcareresearch.co.nz/news/release.asp?Ne_ID=284 |title=New research estimates there are about 30 million possums in New Zealand |publisher=Landcare Research |date=9 December 2009 |access-date=6 April 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111016172446/http://landcareresearch.co.nz/news/release.asp?Ne_ID=284 |archive-date=16 October 2011}}

Economic uses

File:Trichosurus vulpecula (New Zealand) fur skin.jpg

An industry using fur pelts and wool mixed with possum fur fibre has developed, with trappers and hunters providing raw material. The fur is often sold as "eco-fur" by a number of manufacturing and retailing businesses. Possum hairs are hollow, like polar bear hairs, and the wool produced is both soft, and an excellent insulator.{{cite web

|url=http://www.nzgifts-souvenirs.co.nz/industry/#welcomehome

|title=Welcome to New Zealand Possum Products

|publisher=New Zealand Souvenirs Mall

|access-date=10 July 2011

|archive-url=https://web.archive.org/web/20120326195151/http://www.nzgifts-souvenirs.co.nz/industry/#welcomehome

|archive-date=26 March 2012

|url-status=dead

}} The number of animals taken for fur is rising and has almost equaled the numbers killed in poisoning. Several 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".[http://nzpossumproducts.co.nz/industry/links_furother.htm#links-other] {{webarchive|url=https://web.archive.org/web/20071216000559/http://nzpossumproducts.co.nz/industry/links_furother.htm|date=16 December 2007}} There is also a small industry processing possum meat as 'Possyum' dog food,{{cite web|url=http://www.dawsonfurs.co.nz/possyum.html |title=Products - Manufacturers of Possum Fur Products Including Yarn and Duvet Covers |publisher=Dawson Furs |access-date=2017-04-25}} also for export.

=Sport=

In 2010, the Royal New Zealand Society for the Prevention of Cruelty to Animals criticised a number of New Zealand schools that had carried out "possum-tossing contests", which involved throwing dead possums. The society said, "while it's technically not illegal, it's morally wrong to throw a dead animal around". The principal of one of the schools said that the contest helped pupils to engage with the outdoors and had also included education about humane methods of possum control. A local newspaper editorial argued that the schools were in rural areas, which had different practices, "both traditional and otherwise", to those of urban areas.{{cite news|website=BBC News|url=https://www.bbc.co.uk/news/world-asia-pacific-11397239|title=Row over NZ possum-tossing contest|date=23 September 2010|access-date=19 June 2013}}

References

External links

[https://web.archive.org/web/20131226204346/http://www.doc.govt.nz/conservation/threats-and-impacts/animal-pests/animal-pests-a-z/possums/ Possum information] at the Department of Conservation
[https://web.archive.org/web/20081014051138/http://www.maf.govt.nz/mafnet/sectors/animals/possum.html Possum information] at the Ministry of Agriculture and Forestry
[http://www.landcareresearch.co.nz/publications/infosheets/possums/ Possum information sheets and manuals] {{Webarchive|url=https://web.archive.org/web/20060506165749/http://www.landcareresearch.co.nz/publications/infosheets/possums/ |date=6 May 2006 }} at Landcare Research
[http://tbfree.ahb.org.nz/ TB free New Zealand] {{Webarchive|url=https://web.archive.org/web/20110830132306/http://tbfree.ahb.org.nz/ |date=30 August 2011 }} – TB control programme in New Zealand
[https://web.archive.org/web/20110607072212/http://www.doc.govt.nz/publications/conservation/threats-and-impacts/animal-pests/the-use-of-1080-for-pest-control/3-why-we-use-1080-for-pest-control/3_1-possums-as-reservoirs-of-bovine-tuberculosis/ Bovine TB information on Department of Conservation website] – The use of 1080 for pest control in New Zealand – Possums as reservoirs of bovine tuberculosis
[https://web.archive.org/web/20110902201329/http://www.1080facts.co.nz/bovine_tuberculosis_TB Information about bovine TB on 1080: The Facts website] – Facts about how 1080 poison is used to control bovine TB in New Zealand

Category:Agriculture in New Zealand

Category:Nature conservation in New Zealand

Category:Invasive animal species in New Zealand

Category:Invasive mammal species

Category:Possums