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Predators like the he native falcon are very vulnerable to 1080 poison

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Tourists are greeted by the “skull and crossbones” signs everywhere in New Zealand

Possums in Australia are protected in mainland states but in New Zealand just a few hours flight away and in total contrast, the possum is classed by authorities as a destructive pest, sentenced to death by extermination and hounded by mass poisoning efforts.

The sharp contradiction seems bizarre and the more you delve into the New Zealand attitude and policy, it is.

Possums were introduced from Australia to New Zealand in 1837 and subsequent liberations were made well into the 20th century with a view to establishing a lucrative fur trade.

Back in 1917 in New Zealand the Auckland Acclimatisation Society’s Annual Report in discussing possums, said “We shall be doing a great service to the country in stocking these large areas with this valuable and harmless animal.”

Fast forward almost a century to today and New Zealand’s Department of Conservation is adamant that possums are a pest. “Introduced to New Zealand in 1837 to establish a fur trade, the possum has become one of the greatest threats to our natural environment–“the damage to native forests can be seen all too clearly in many areas.”

The department is not alone in its hatred of possums. Possums allegedly spread bovine TB, a disease of cattle and farmed deer says the agency TB-Free NZ . The agency says “Although we target possums for TB control, wherever possible we work closely with DOC to ensure a ‘triple hit’ of the worst mammalian pests. Our efforts in this area have been commended by the country’s biggest conservation organisation, Forest and Bird.

Fired by this zeal and belief, the government is bombarding New Zealand’s countryside with aerial spreading of the controversial 1080 poison.

But are possums really a pest?

Over 50 years ago, I wrote an article for a national magazine titled “A query about the Possum – has it’s danger been exaggerated?” Interestingly the article drew no comment and I have not changed my views since, in fact probably only reinforced them.

First a quick background on the controversial 1080 poison.

It was originally developed as an insecticide in the mid-1920s but was found to kill anything and everything that came in contact with it. So it became, in use, an animal poison. But its original use still remains. It kills all insects, worms and other invertebrates which are the food of birds ranging from New Zealand’s native birds such as kiwi, bush robins, fantails and others.

Secondly 1080 is a slow killer. Unlike the instant killing by cyanide, 1080 takes up to about 48 hours to kill. So a mouse slowly dying and struggling will be picked off by predators such as falcons, hawks, New Zealand’s native owl called the morepork and others.

Thirdly 1080 is a “secondary” poison. i.e. the owl (morepork) that grabs the slowly dying poisoned mouse becomes poisoned with 1080 too. So too does a scavenger such as bush hen (weka) or mountain parrot ( kea) dining on a poisoned possum or deer carcass.

Fourthly 1080 based on limited research on mallard ducks in sub-lethal doses (not enough to kill) reduces or eliminates fertility in the male of a species. Thus sub-lethal doses to any birds will lower their breeding rate because males become infertile. It’s known as an endocrine disruptor – New Zealand refuses to do the science on it.

The unavoidable conclusion is that the 1080 poison kills not only possums but other life from insects to native birds to wild game such as deer while undermining the reproductive breeding cycle of most species.

Let’s look at the first two assumptions …

The spreading of poisons in New Zealand has been done for about 60 years on a trio of assumptions (a) there are 70 million possums spread evenly over New Zealand (b) possums are a “rapacious consumer of foliage” and (c) possums are the major vector (spreader) of Tb in farmed animals.

Let’s look at the first two assumptions.

Firstly the “70 million possums” are destroying forest. A few years ago I discovered details of a 1994 Department of Conservation workshop titled “Possums as Conservation Pests”.

A respected scientist Graham Nugent of New Zealand’s Landcare Research, spoke to the workshop and told it the 70 million possum figure was flawed describing it as a “back-of-a-cigarette-packet” calculation.

But even if the highly exaggerated 70 million figure was used, the marsupials would “apparently consume about 21,000 tonnes of vegetation per day” based on 300 g wet weight of foliage consumption per possum multiplied by 70 million.

Nugent said “This oft-quoted (70 million) figure is frequently used to depict possum as a rapacious consumer of all things green.”

But, added Graham Nugent the trees’ daily foliage production is 300,000 tonnes for forests alone. In short, the fictitious number of 70 million possums would gobble only about 1/15th or 7 percent of the new foliage each night.

Indeed it would be less because most possums live near margins of forests adjoining paddocks rather than in the forest and a significant part of their diet is grass or spring and summer growth on farm trees like willows, growing outside the forest.

Graham Nugent continued to say that possums do not threaten the total national forests by deforestation. For the bulk of New Zealand’s forest, the process is one of a change in individual species known as composition. There would be less of palatable vegetation species. So the change is merely a structural forest change.

Possum numbers in New Zealand’s rugged country are usually “controlled” by Nature’s rigorous environment especially climate. In inclement weather, natural mortality of possums may be as high as 40 per cent.

A study in 1958 in a then rarely visited part of New Zealand’s rugged Fiordland massif showed Nature without Man’s interference, balances wild animal numbers to the habitat’s carrying capacity. Scientist Thane Riney in his classic Fiordland Lake Monk research showed deer and possum populations left to Nature, peaked and then fell to a low stable level. Any wildlife population acts the same.

New Zealand’s possums probably reached their peak decades ago and have since been in a gradual decline until they achievede “joey” a year. Yet the Department of Conservation and TB Free NZ frequently whip up a fictional fear by claiming possum numbers are building up and more 1080 should be dropped. In any case, if numbers were to increase, harvesting of possums by commercial fur trappers at no risk to other wildlife is an obvious option.

Besides the possum is a resource with possum fur worth $110 a kilogram compared to $3 a kg for crossbred sheep wool. Possum fur is blended with merino wool and has a significant market in “added value” fashion clothing.

The meat of possums has also value for either pet food manufacture or as meat for human consumption. One New Zealand pet food manufacture had a thriving market in Japan for pet food utilising possum. Almost without warning his export market to Japan was cancellled overnight when the Japanese market saw on television a news item about New Zealand dropping 1080 on forests.

Even some government sources have been sceptical …

Evidence that possums are not damaging forests is evident in New Zealand’s early pioneering days. One early missionary explorer William Colenso’s travelled the Ruahine mountain ranges in the mid-19th century. Colenso’s diaries vividly told of forest damage from periodic storms and giant land slips long before any possums or deer were introduced.

Possums are accused of being a spreader of bovine Tb in farmed cattle and deer herds. But even some government sources have been sceptical. New Zealand’s Treasury in 2000 in a paper “Coughing Up for Tb control” raised serious doubts about the role of possums in bovine Tb infection. It suggested “that Tb was spread by transport of infected animals”, i.e. on stock trucks and not possums.

Also revealed was that the skin test used to test farm stock for TB has an error of 20 per cent when there is a much more accurate blood test with an error rate of only one per cent. Critics say the inferior test is used to prolong the existence of TB in herds so as to give reason for bureaucracies to continue.

Conservationist and Bill Benfield author of the provocative conservation book “The Third Wave” says New Zealand could get rid of bovine Tb immediately.

“Australia has possum — yet they got rid of bovine TB without poisoning wildlife” then dryly added, “but Australia does not have a bureaucracy like the Animal Health Board (now TB Free NZ) propping up its own existence.”

In October 2001, I listened to Dr Frank Griffin of Otago University addressing a deer farmers’ function. The scientist said that New Zealand’s pest management strategy focused narrowly on “killing possums and skin tests” and was not the solution to the Tb problem. Dr Frank Griffin saw the long term, logical solution for deer farming as selectively breeding genetically Tb resistant deer, but was refused funding while annually millions of dollars were spent by AHB and DOC spreading 1080.

Bill Benfield says the belief that there is a possum problem is an excuse to dump more 1080 poison. Therein the plot thickens.

Animal Control Products is a company that processes imported raw 1080 poison and incorporates it into bait form for aerial scattering. Who is behind the company? None other than the New Zealand government.

Economically crazy; environmentally crazy …

It is a “state owned enterprise” charged with making maximum profits by selling 1080 poison to the government agencies to spread.

Economically crazy? Yes. But then dropping 1080 is environmentally crazy.

In amongst the bizarre illogic are strident, vocal groups obsessed with “anti-exotic animal phobia” a term an American professor of zoology in 1958 used to describe New Zealand’s attitudes to wild animals. Among the groups are the long standing Forest and Bird Society with very recently formed groups such as Predator Free NZ. “Predator-Free New Zealand is a grass-roots movement aiming for the large-scale suppression or eradication of rats and mice (rodents), stoats and ferrets (mustelids), and possums across the New Zealand mainland” says google blurb.

As unscientific as it is, PFNZ even has the backing of a number of scientists from Landcare Research such as Andrea Byrom. Yet Graham Nugent earlier quoted, saying possums are not a conservation pest, is from Landcare Research. Puzzling? Yes. But then the whole fiasco is in its contradictions, cross currents and the catastrophe of mass poisoning of New Zealand’s natural ecosystem.

Adding another piece to the jigsaw puzzle is that Fish and Game NZ, charged with managing the fishing and shooting public’s waterfowl and upland game resources and trout fisheries, is incongruously a member of PFNZ.

Yet 1080 poison is known to kill game birds such as chukor and quail and probably pheasants. And it may effect trout although no one knows. Research is lacking. Certainly filming after a 1080 drop by two brothers Clyde and Steve Graf showed eels, crayfish and smelt feeding on poisoned baits and toxic carcasses. Eels that were analysed after 1080 drops showed 11 times permissible levels of the toxin, yet their flesh still forms the basis of an export food industry.

Frequently critics ask about the credibility of the country’s much vaunted, “100% pure” that is the branding for selling exports and enticing tourists. Ironically tourists frequently encounter warning signs depicting a skull and crossbones and warning of the dangers of 1080 poison.

Meanwhile New Zealand blunders on committing environmental destruction and now even selling its “poisonous expertise” to other countries who are showing symptoms of exotica- phobia and its accompanying hatred based on imagined invasive and predator species.

Tony Orman, a New Zealand conservationist and outdoor sportsman is the author of over 20 books mainly on outdoors.

• Morton Bartlett, in Comments: Nailed it in one, this stuff is slowly killing this country, species by species

• John Hayward, in Comments: I have yet to see a Tasmanian official admit 1080 causes residual tissue damage at sub-lethal dosages, nor is there any acknowledgement that baits scattered on the ground might be taken by birds. What passes for tough-minded pragmatism in Tas looks a lot like the condition known elsewhere as stupidity.

• Mary Molloy, in Comments: I am a farmer who farmed for over 40 years without TB but with an abundance of possums some years before the massive poisoning from squads of helicopter, firstly from fixed wing planes but now helicopters. We had a vibrant birdlife and over abundance of possums and no TB. Now we find possums very rarely, poor bird numbers except the opportunist sparrows, magpies, starlings etc. On our second farm we had a case of Tb which is now proven to have been bought in, a risk we knew we took. We however checked every group of new cattle ourselves, with local vets and with AHB which is now TB Free – we still got one with TB as our systems in NZ are not open enough nor good enough at identifying risk areas, its a bloody big secret and we are noted proactive people. Tb is a farmer problem, it is not a bush problem, possum problem, goats problem or anything else problem …