Perth River
Image: Jack Mace | DOC

Archived content: This media release was accurate on the date of publication. 


DOC has given permission for Zero Invasive Predators (ZIP) to undertake a predator removal programme over 12,000 ha of conservation land in the Perth River valley in South Westland.

Date:  21 February 2019

ZIP has been working at several sites in New Zealand to develop new methods and devices that completely clear areas of pests, towards the country’s predator free goal.

The programme of work in the Perth River valley aims to completely remove possums and potentially rats, and significantly reduce stoats, from the research area. It will also establish a network of devices to detect any survivors or invaders, and use ‘spot treatments’ to remove them before they re-establish a population. Preparation for the work will start shortly and the predator removal operation will go ahead in March.

DOC previously gave ZIP permission (April 2018) to carry out the aerial 1080 component of their predator removal programme, but the operation was cancelled due to poor weather.

DOC West Coast Director Mark Davies says ZIP has worked with DOC scientists to research methods involving the use of a bird repellent and tahr carcasses to reduce the risk to kea from 1080 poisoning during the predator removal operation.

“There’s no doubt that this operation poses a risk to the kea in the valley, but I’m satisfied that use of the bird repellent to train kea to avoid baits, and tahr carcasses to attract kea away from baits, will help to mitigate these risks.

“These methods performed well in trials over the last few months and their use in the ZIP predator removal operation will enable further testing in the field.

“ZIP’s Perth River valley ‘remove and protect’ programme has enormous potential to advance our knowledge in the quest towards achieving a predator free landscape where native wildlife will be able to thrive,” says Mark Davies.

ZIP will monitor 15-18 kea through the 1080 operation using radio transmitters to test the effectiveness of the mitigation measures and will report the results to DOC before commencing the second round of treatment.

ZIP has worked closely with DOC and has the support of Te Rūnanga o Ngāi Tahu (TRONT) and Te Rūnanga o Makaawhio, Forest and Bird, Federated Mountain Clubs (FMC), the Tai Poutini West Coast Conservation Board and New Zealand Deerstalkers Association (NZDA).

Background information

The method of applying 1080 developed by ZIP to remove predators differs from standard DOC predator control methods with two pre-feeds of non-toxic bait before the application of toxin, which is applied firstly at double the standard rate, followed by a second treatment a month to six weeks later, applied at the standard rate.

Kea aversion training with repellent-laced non-toxic baits placed next to tahr carcasses and then distributed more widely, will take place prior to 1080 treatment. The repellent baits (using anthraquinone) make kea feel sick and train them to avoid the later sowed toxic baits. 

Captive trials showed lacing bait with repellent reduced the level of interaction by kea with bait. The work done with the repellent-laced baits show the majority of kea actively avoid them once they have tried the baits. ZIP field trials have also shown tahr are a preferred food source for kea, which will strip a carcass bare in just a week and ignore bait nearby when given a choice.

The kea population in the Perth River valley is in relatively high numbers with a good mix of juvenile and adult birds. There’s strong evidence that the natural barriers provided by the valley’s big rivers and the Southern Alps/ Kā Tiritiri o te Moana, in combination with DOC’s previous aerial 1080 operations in the area, have benefited kea and other native species in this area.


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