A new approach to possum control in the Tararuas

26 May, 2005

A new approach to possum control in the Tararuas

The Department of Conservation is increasing the frequency of possum control in the Tararua Forest Park to better protect native birds and forest canopy.

The core operations will now be carried out by aerial application of 1080 baits, and the department-led ground control that has been carried out in Tararua Forest Park will cease.

“Over the past 10 years, the department’s possum control operations had successfully protected high-altitude forest, including the vulnerable tree fuchsia forest,” DOC Wellington conservator Allan Ross said.

“This gives us confidence to consider more ambitious levels of protection. The department is now extending protection to native fauna in the lower-altitude forests, while continuing to protect canopy trees in the Tararuas.

“We want to seize the opportunity to protect a wider number of native animals and threatened plant species, as well as increase forest canopy protection throughout the Tararua Range.”

To do this the department has designated two types of management areas: canopy protection zones and a biodiversity zone.

Most animal pest control operations in the Tararuas will be in six canopy protection zones, of up to 11,000 hectares each. The frequency of possum control operations has been shortened from a seven year to a six year return time in these zones.

There are three zones on each side of the Tararua Range encompassing all the major Tararua catchments.

In addition a biodiversity zone of up to 4000 hectares within the Otaki catchment will be treated by the aerial application of the pesticide 1080 every three years. This will be done in spring to target rats as well as possums, providing protection to native birds and other fauna during the crucial breeding and nesting period. By reducing the number of ship rats and possums in this area, native birds such as tomtits and whiteheads will be free of predation to breed for part of their nesting season for that year. This is expected to boost their numbers in the long term.

The Otaki catchment was selected because of its high biodiversity values and its accessibility to the public, Mr Ross said.

Birds and forest plants, and possum and rat numbers will be intensively monitored to determine the effectiveness of control operations

DOC hopes to begin operations in the Otaki Biodiversity Zone in 2006/07.

Canopy protection zone operations will commence in the first favourable weather opportunity between July 1 to December 9, 2005 in the Tauherenikau and Waiohine Catchment.

Cereal baits containing small quantities of the pesticide 1080 will be distributed by helicopter over an area of up to 11,000 hectares.

There is no risk to people visiting the treated area providing they do not eat the bait. However dogs are extremely susceptible to 1080 through either eating bait or from scavenging on poisoned carcasses. While the baits themselves break down quickly after rain, the area will remain hazardous to dogs until possum carcasses have decomposed, perhaps for more than six months. There will be warning signs at entry points into the park reminding people of these risks.

(Refer to the accompanying media release DOC protecting forest canopy in the Tararuas and fact sheet Key facts about possum control in the Tauherenikau and Waiohine catchments, Tararua Forest Park for further information on this operation.)

Fact sheets about the changes to the Tararua Forest Park possum control regime can be found on the DOC website www.doc.govt.nz (regional info > Wellington > publications) or obtained from the local DOC offices.

More information about possum control and the devastating effects of possums on our native forests can be found on the DOC website: www.doc.govt.nz (conservation>animal> pests>possums) and at the local DOC offices.

Facts about 1080

What is 1080?

1080 (ten-eighty), or sodium fluoroacetate, is one of 10 pesticides used in this country for killing introduced mammalian pests. 1080 occurs in nature as a plant toxin called fluoroacetate. It is found in a number of plants (including the tea plant) in South Africa, South America, and Australia. The toxin is thought to have evolved as a deterrent to browsing animals. 1080 is biodegradable so does not accumulate in the environment.

Why does DOC use 1080?

The Department of Conservation (DOC) uses 1080 to counter the devastating effect that high numbers of introduced possums are having on native plants and animals. In many areas possum browsing threatens kamahi and rata forests with collapse and the endangered mistletoe with extinction. Possums eat threatened giant land snails and the eggs of kiwi, kokako and kereru, and they compete with kaka for food.

1080 is particularly suited for use in New Zealand because unlike other countries it has no large native ground-dwelling mammals that can be affected by its use (New Zealand's two bat species are not considered susceptible to the poison). Of the available poisons, 1080 is the only one licensed by the Pesticides Board to be spread from the air. This factor and its low cost compared with other pesticides, makes 1080 a cost-effective tool for possum control over the large areas of terrain DOC administers.

Where does DOC use 1080?

Nationally, aerial 1080 operations account for about half of DOC's possum control operations. These generally take place in large, remote areas where ground control is impractical. An example is the West Coast, where aerial 1080 operations account for about 80% of conservation possum control work. 1080 is also used by operators working areas on foot.

Does 1080 kill native fauna?

Possums, stoats and rats are the number one threats to native birds, not 1080. 1080 baits are dyed green and flavoured with cinnamon to make them less attractive to birds. Individual birds may be poisoned but these numbers are exceedingly low. In a recent operation, 41 kiwi monitored using radio transmitters all survived a 1080 possum control operation.

Extensive monitoring of tomtit populations in Tongariro Forest before and after a 1080 operation in 2001 show that no adverse impacts occurred. This is significant because tomtits and other passerines such as robins that feed on the forest floor are considered vulnerable to poisoning.

Research shows native bird populations bounce back significantly when possums are reduced to low numbers. For example, monitoring of native robins after a 1080 operation in Pureora Forest in 1997 showed 67% nesting success in the treated area, compared with 30% in the area without possum control. A year later, robin populations had increased 37 % in the control area compared with 16.3% outside. Studies have also shown that 1080 does not have any detectable impact on short-tailed bats.

Does 1080 persist in soil?

1080 is biodegradable so does not persist in soil. In favourable conditions soil micro-organisms break down 1080 to safe naturally occurring substances in about two weeks, although this is greatly hastened when it rains. 1080 operations are usually conducted in winter and spring when wetter conditions assist rapid breakdown.

What is the fate of 1080 in water?

Traces may be found in water soon after contact with 1080, but these soon dissolve and break down to immeasurable levels. Between 1990 and 2002, over 1400 water monitoring programmes were undertaken after aerially sown 1080 bait operations. These showed no results of any concern for public water supplies and no evidence of prolonged 1080 contamination in surface or ground waters. In aerial operations a minimum 20 metre '1080-free' area is often enforced around waterways specified by the Medical Officer of Health.

The use of sophisticated GPS technology helps ensure the bait drops occur away from the specified waterways. It is also worth noting the example of Perth, Western Australia. In the Perth water catchment, fluoroacetate concentrations in leaves of some members of the Gastrolobium plant family are several hundred times higher than concentrations of 1080 applied in aerial operations (5-10 grams per hectare) in New Zealand. Fluoracetate has never been detected in the Perth water supply.

How is public safety ensured?

DOC is legally bound to meet strict Ministry of Health conditions before permits for 1080 operations are issued. In addition, the Department has its own stringent requirements (set out in standard operating procedures) which must be met. Measures to ensure public safety include community consultation processes, public notification through the media and signs in possum control areas. 1080 is a controlled substance under the Pesticides Act and can only be applied by licensed operators. Regional and Unitary councils and local authorities often also require a resource consent or certificate of compliance for aerial operations.

What are the risks to pets and livestock?

Dogs are ten times more vulnerable to 1080 than possums and are readily killed by consuming 1080 baits, or possums killed by 1080. Dogs must be kept away from areas treated with 1080, and kept on a leash or muzzled until the area is safe. 1080 is also highly toxic to livestock so farmers must keep animals away from control areas. 1080 is eliminated from the tissue of animals that consume a non-lethal quantity, and there are no lasting effects.

Is 1080 used in other countries?

1080 is used in Australia, Mexico, Japan, the United States and Israel. In many countries, including the United States, 1080 use is restricted because of its effects on native mammals. In New Zealand, where there are no native mammals other than bats, we do not have this complicating factor.

ENDS

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