Yes, Brushtail Possums are a destructive pest in NZ. Probably the most relevant and credible authority on the centuries old problem of human introduced possums into New Zealand should be New Zealand's own Department of Conservation (DOC).
Yet DOC has no watchdog to vet its possum control policy, to evaluate the ethics of its indiscriminate aerial 1080 poison programmes, its budget decision making, its pest control methods. DOC is its own master, answerable to no-one. It dictates possum control and culling only on the basis of it deeming it administratively cost effective and efficient. Perhaps this is a leftover culture of Rogernomics applied to lean management of New Zealand's ecology.
On the DOC website the possum problem in New Zealand is clearly explained. An issue this author accepts as a serious ecological problem facing New Zealand.
Under the heading 3.3 Possum damage to native forests, the possum problem in NZ is explained as follows:
"Over the past 50 years, possums have emerged as one of the major threats to the health and wellbeing of forests throughout New Zealand. Many of these impacts are subtle and indirectly affect native birds and insects. Possums cause damage to native forests from the ground level to the canopy where, by concentrating on individual plants of their preferred species, they can kill trees by defoliation over several years. Possums preferentially feed on some of the tall canopy species – such as tawa, northern rata, kohekohe, southern rata, kamahi, pohutukawa and 20 Hall’s totara – while ignoring others. They also prefer some of the smaller trees, such as tree fuchsia and wineberry, along with mistletoe, forest herbs, some ferns, and a number of endangered shrubs.
It is difficult to imagine that possums, which are about the size of a large cat, can kill individual trees that have dominated forest landscapes for centuries before possums were released here. But when the number of possums is combined with the total amount each one eats, their impact on their preferred species is easier to appreciate. The amount of food consumed by an adult possum each night is about 160 gm of digestible dry matter. There are probably tens of millions of possums living in native forests. In total, possums are consuming thousands of tonnes of vegetation each night.
Possum populations have now modified many New Zealand forests. The rate and extent of these changes vary widely between different types of forests. Beech forests are the least affected, but in the vulnerable southern rata-kamahi forests of Westland many valleys have lost between 20% to 50% or more, of their canopy trees. In severe situations, possums have caused the complete collapse of the canopy within 15–20 years of their arrival. Tall forest is then replaced by shrublands.
While the impact of possums is most visible and dramatic when it involves canopy trees, their most pervasive impacts are often less visible. Possums have recently been described as “reluctant folivores”. This means that possums prefer to eat other forest foods than the leaves of trees. Flowers, fruit, leaf buds, fungi and insects are all highly favoured. The consumption of these foods has the largest impact on the healthy functioning of forests and the animals that rely on them. The consequences of possums concentrating on these foods are:
Loss of flowers:
•preventing the formation of seeds
•removing nectar sources for birds and bats
•reducing the food supply for many invertebrates
•nectar loss reducing food supplies for chicks, e.g. kaka, tui.
Loss of fruits:
•reducing food supplies for birds and invertebrates
•affecting bird breeding condition and nesting success, e.g. kakapo, kereru
•reducing or eliminating seed dispersal
•reducing the regenerative capacity of native plants.
Loss of new shoots:
•reducing the ability of plants to overcome leaf loss from weather and seasonal patterns
•reducing numbers of new leaves, jeopardising plant health."
DOC also states that "the damage to native forests can be seen all too clearly in many areas. Possums ignore old leaves and select the best new growth. In some areas they have eaten whole canopies of rata, totara, titoki, kowhai and kohekohe.
Possums compete with native birds for habitat and for food such as insects and berries. They also disturb nesting birds, eat their eggs and chicks and may impact on native land snails. DOC cites examples of natural vegetation damaged by possums at Pirongia Forest Park, and the upper canopy of NZ native forest trees on the slopes of Mt Karioi, south of Raglan."
So, assuming DOC's account is correct, the introduced Brushtail possum is a serious pest to New Zealand (NZ) native ecology. But what to do about it?
The repatriation option
It's long overdue for the New Zealand Government to get serious about its self-caused possum problem and look to resolve it once and for all for the benefit of the New Zealand ecology and the possums themselves. It needs to look at the root causes. The possum was introduced to New Zealand by New Zealand profiteering colonists. It is not the possum's fault it is in New Zealand.
Pouring $80 million a year of taxpayers money into cruel indiscrimate aerial baiting is not working. If it was the possumproblem woudl be reducing and there would not be a burgeoning possum fur trade.
Instead of perpetuating a 19th Century immoral fur trade, in order to control possums and other introduced pests in NZ, one option is to catch and relocate them back to their native home country habitat. This may seem highly expensive and labour intensive and far fetched, but what other option is both humane and effective?
It's not the possums' New Zealanders introduced them from Australia to New Zealand. The problem is an inherited inter-generational problem caused by New Zealand colonists. It shoud be solved by their descendants, not perpetuated as a fur trade.
Questioning DOC's claims of Humane Possum Control
Acknowledging the possum in NZ is an introduced pest, the question in this case is whether the possums in New Zealand are being killed humanely and whether this is being effectively monitored by a government watchdog worthy of the public trust?
By killing possums, humans have a moral obligation to do it humanely. Possums like all animals feel pain, fear and suffering.
But in NZ, DOC's officially choice of death is aerial baiting with the the literally chaep and very nasty poison '1080' ('ten-eighty', or Sodium Monofluroacetate). DOC's argues it is humane and safe.
Heading out to drop 1080 poison across NZ forests
But The World League for Protection of Animals argues otherwise and offers the following explanation about '1080' poison.
"1080 (sodium monofluroacetate) is a cruel and indiscriminate poison used to ‘remove’ unwanted populations of animals.
Banned in most countries, 1080 is still used liberally throughout Australia to control so-called ‘pest’ species, and reduce ‘browsing damage’ caused by native animals on private land.
1080 poison is a slow killer. When ingested (usually through baited food) the animal suffers a prolonged and horrific death. Herbivores take the longest to die – up to 44hrs, while carnivores can take up to 21hrs before finally succumbing to final effects of the poison. The speed of death is dependent on the rate of the animals metabolism.
A Slow & Horrific Death
Witnesses to the deaths of herbivorous animals, such as macropods, have reported:
"Affected wallabies were sometimes observed sitting hunched up, with heads held shakily just above the ground. Generally they appeared non-alert and 'sick', with shivering or shaking forelimbs and unsteady balance. Most individuals then experience convulsions, falling to the ground and lying on their backs and sides, kicking and making running motions with their hind legs before dying. Many individuals also ejaculated shortly before death, and, with others, exuded a white froth from their nostrils and mouth."
Carnivorous animals such as dingoes, dogs, foxes, and cats become very agitated, as they tremble, convulse and vomit.
The list of symptoms include:
"…restlessness; increased hyperexcitability; incontinence or diarrhea; excessive salivation; abrupt bouts of vocalization; and finally sudden bursts of violent activity. All affected animals then fall to the ground in teranic seizure, with hind limbs or all four limbs and sometimes the tail extended rigidly from their arched bodies. At other times the front feet are clasped together, clenched or used to scratch frantically at the cage walls. This tonic phase is then followed by a clonic phase in which the animals lie and kick or 'paddle' with the front legs and sometimes squeal, crawl around and bite at objects. During this phase the tongue and penis may be extruded, their eyes rolled back so that only the whites show and the teeth ground together. Breathing is rapid but laboured, with some animals partly choking on their saliva. Finally such individuals begin to relax, breathing more slowly and shallowly and lying quietly with the hind legs still extended but apparently semiparalysed".
From the above descriptions, it is without question that 1080 poison inflicts great pain and suffering on affected animals. Aside from the physical pain endured over the many hours before death, the terror, fear and anxiety felt by these animals is unimaginable."
The main reason DOC uses 1080 is because it is cheap. Dropping it it indiscriminately by air is efficient and convenient.
Setting caged traps for possums is expensive. Using poisons that act faster that 1080, sush as cyanide is also more expensive.
So DOC's key justification for its use of 1080 is one of cost. DOC also justifies using 1080 because other countries use it for pest control, like Australian & the USA , so implying that 1080 must therefore be ethically acceptable. But New Zealanders should make up their own mind and should recall that both the USA and Australia used Agent Orange in The Vietnam War.
DOC also justifies 1080 use because NZ has no natural mammals so the risk to non-target species are nil. But this claim is FACTUALLY INCORRECT!
On 30 July 2008, The Dominion Post reported that after a DOC aerial drop of 1080, seven kea had died at Fox Glacier from eating the 1080 poison, wiping out almost half a group of the endangered and protected parrot being monitored by the Conservation Department. DOC came up with excuses, but with such an endangered bird with so few kea left on the planet, DOC cannot afford to gamble with the kea's extinction.
Anti-1080 campaigner Mike Bennett said the kea deaths were the tip of the iceberg. "These are only the monitored ones. If that percentage is extrapolated for the entire population, that doesn't leave many for the next drop" and has called for a ban on all aerial 1080 drops in alpine areas.
NZ's Commercial Possum Fur Trade
New Zealand's own backyard fur trade has seen a recent resergence since the 1830s when New Zealand hunters first introduced the possum to the wilds of New Zealand. the traditional method of possum slaugher is by trapping. For nearly two centuries the cruel 'gin trap' with serrated jaws was used. Although the trapping laws have recently banned gin traps, leg-hold traps remain the method of choice for trappers.
According to the NZ Lifestyle Block website:
"Leg-hold traps such as the Lanes Ace or gin trap have been widely used for possum and rabbit control for many years. The gin trap is more than 10.5 cm across its open jaws, which are serrated, and it is powered by a flat metal spring, so it's a "size 1½ long spring" trap.
Traps of size 1½ or larger are more likely than the smaller traps to snap shut across the belly or chest of an animal. Although larger traps have been banned, traps of size 1½ can still be used if they are powered by double-coil springs. From January 2011 they will have to be padded, and you can't modify them yourself to make them padded...
Why are these traps cruel?
When the gin trap snaps shut on its victim, the teeth bite into the skin and can cause a lot of trauma and no doubt agonizing pain. All leg-hold traps are indiscriminate about what they catch. If they are set in possum tracks or runs it's more likely than not that any catch will be a possum, but it might also be a cat, hedgehog, rat, bird or small dog. Large dogs can sometimes pull out of them but they may be injured in the process.
Icing sugar or flour around traps is sometimes used to attract possums, but if used beneath a trap the animal is likely to be trapped by its snout or head.
What are the alternative leg-hold traps?
(In NZ) it is still legal to use size 1 leg-hold traps such as the Victor within the restrictions on location and setting described above. It is smaller than the gin trap and doesn't have serrated jaws. The Victor No 1 can be bought with cushioned inserts that make it more humane. It tends to cause less frequent and less severe injuries than the gin trap and larger leg-hold traps, but it can still cause severe bruising, and trapped animals will sometimes cause themselves severe injuries in their struggle to get free.
Trappers favour the Victor No 1 because it is compact, light and relatively efficient. The changes in the legislation mean that it is likely to become even more popular.
There's good advice for landowners on the most humane way to use leg-hold traps and their alternatives on the National Possum Control Agencies website (www.npca.org.nz), and not just for possums but for ferrets too."
Typical traps used in NZ for possums are the flat jaw/leg hold' type such as the the Bushmaster. While recognised as more humane that the serrated jaw 'gin trap', it can still cause suffering to a trapped animal, and of course is indiscriminate.
The Hamilton City Council prohibits the use of leg-hold traps such as gin traps in residential areas and within 150 metres of dwellings or places where there are likely to be pets. It instead recommends cage traps and Timms traps for possums and other feral animals.
Feratox (encapsulated cyanide)
According to the Lifestyle Block website NZ veterinarian Dr Marjorie Orr, BVM&S, PhD, BA and lifestyle farmer on , the most humane method of possum control is to use Feratox capsules, which is an encapsulated cyanide. The preferred baiting method is to use these in specially designed "bait stations or sachets stapled to trees, baited with peanut butter (possums like it and dogs and birds usually don't). The pest control companies that put out the poison will usually on request remove the sachets after a few days, and this helps reduce the risk of accidental poisoning of other animals. The poison in the capsules, cyanide, is quickly destroyed on exposure to air. Death is quick and relatively stress-free and there is no risk of secondary poisoning of dogs that scavenge poisoned carcases."
The test of humane killing must be conditional on the absence of pain and stress caused to the animal and that the killing be very quick.
But the killing of a native animal is wrong, despite it being introduced by humans. It has become a convenient excuse for New Zealanders to kill possums. Possum control by either DOC or the fur trade is not effective and in both cases teh chosen methods are inhumane. New Zealand's possum problem has been allowed to escalate into an immoral industry for profiteers. The New Zealand Government is responsible for failing to deal with the problem effectively and humanely. It has perpetuated an immoral fur trade that begun in the 19th Century, and at the same time allowed much irreversible harm to be caused to New Zealand's fragile ecology.