The Most Complex Island Pest Eradication ever attempted!

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The massive $3million Pest Eradication programme currently taking place on the islands is the most complex island pest eradication ever attempted any where in the world according to the Department of Conservation

It is being carried out to rid Rangitoto and Motutapu of animal pests that eat birds and insects. The forest will flourish as a result.

Information at a glance:

• Helicopter aerial drops covered both Rangitoto and Motutpau islands, a total of 3842 hectares.

• Three aerial drops were operated between June and August, winter 2009, when food was at its scarcest, rat numbers were at their lowest and their hungriest

• The 3 helicopters operated simultaneously and used spreader buckets and GPS technology to drop the bait as part of three separate applications which lasted lasting 2-3 days. There was a minimum of two weeks between applications

• Total number of days required for bait application was 6 days; up to 140 tonnes of bait was dropped. Between 200-300 helicopter flights were required. Both islands were closed for a week following the bait applications to ensure public safety

• DoC is the world expert on island pest eradications – they have already successfully completed 90 island pest eradications. The largest was Campbell Island (11300ha) completed in 2001

• The overall eradication exercise may take up to 4 years, following the aerial drops, to complete. This is very much dependant on the success or otherwise of the aerial drop. These subsequent years will be taken up with shooting/trapping survivors, gassing rabbit burrows etc..It took 10 years to totally eradicate the last remaining possums and wallabies on Rangitoto! The poison was delivered in the form of a blue/green coloured cereal pellet. The colour is intended to deter birds.

• The active ingredient was brodifacoum and targeted ship and Norway rats as well as mice

• The aerial operation was supported by the hand laying of bait in buildings, all covered structures.

• The poison can stay active up to 4 months but does break down very quickly in the rain

• Brodifacoum is one of the world’s most widely used rat baits. You can buy it locally (brand names Talon and Pestoff), you do not need a license.

• Can take around 4 days to kill a Norway rat following ingestion

• No residues of brodifacoum have been detected in water samples following pest eradication operations in New Zealand

• Cats, stoats will die from secondary poisoning, eating dead or dying rats.

• Rabbits and hedgehogs will likely eat the bait. We expect the rabbits may hoover up the bait before the rats and mice get to it. This issue was addressed by increasing bait sow rates

The project represented the largest island based eradication program of its type in the world and will have a profound effect for both islands as it allows the reintroduction of indigenous fauna to complement the aggressive planting programme being undertaken by MRT.

DoC has stated that due to the very large pastures available for reforestation, Motutapu could eventually host the largest population of kiwis in New Zealand as a large island sanctuary.  Given the uneven success of predator proof fencing on the main island sanctuaries, island sanctuaries are increasingly seen as having the greatest potential to protect the countries endangered flora and fauna.

Project Hauraki

The most ambitious "Project Hauraki" initiative is the ecological restoration programme for Rangitoto and Motutapu islands. This restoration involves removing all seven remaining mammal pests from both islands, in a bid to create the largest pest free island habitat in the Hauraki Gulf.

This is the most complex island pest eradication the department has ever attempted in terms of the range of pest species, the size of the islands and the difficulty of the terrain on Rangitoto.

DoC is a world leader in island pest eradications with experience of more than 50 successful island pest eradications in New Zealand, and is confident that this eradication will be successful.

The programme of work to investigate the feasibility of restoring these iconic inner gulf islands was announced in 2008 by the former Prime Minister Helen Clarke and the former Conservation Minister Chris Carter.

Eradicating pests from Rangitoto and Motutapu is a key step in the ecological restoration of these beautiful and popular Hauraki Gulf islands. It builds on decades of conservation work by both DOC and the community, including removal of possums and wallabies, re-planting parts of Motutapu and weed control on both islands.

This restoration work will allow the reintroduction of  species such as kiwi, kaka, tuatara and mistletoe in the future. Native bird populations on the islands such as the endangered NZ dotterel, kereru and white fronted tern will be safe from stoats, rats and feral cats. Rangitoto's unique pohutukawa and rata forest would be able to grow undisturbed by rodents and rabbits.

Rodents are the most difficult pests to remove, and consequently they were targeted first.

The Rangitoto and Motutapu restoration programme is a flagship project for the Hauraki Gulf Marine Park. Restoring Rangitoto and Motutapu and repopulating them with native species will be a huge draw card for visitors. Combined with other pest-free islands in the Marine Park - Tiritiri, Matangi, Motuora, Little Barrier and Motuihe - the Gulf will truly be a centre for island restoration.