Archives For Mice

After 18 long months, the wait is finally over. In just over one week’s time, a team are heading back to the Antipodes Islands to discover the outcome of the Million Dollar Mouse project.

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Following three years of planning, the Million Dollar Mouse team is getting ready to depart for Antipodes Island this week where they will carry out major pest control operations over winter.

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Research from scientists John Marris and James Russell has confirmed the devastating impact mice have had on the unique invertebrate species on the Antipodes Island.

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Good news for the Million Dollar Mouse project, with Bollons Island, the second largest island of the Antipodes group, declared mouse free.

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Restoring globally important conservation sites is just one of Ranger Stephen Horn’s skills. Add climbing mountains, candling kākāpō eggs, and collecting tortured bonsai trees… and we’ve got a man worth reading about!

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Keith Broome is part of DOC’s Island Eradication Advisory Group (IEAG), which provides expert knowledge to help rid pests on islands both in New Zealand and across the world.

Today, Keith tells us about his trip to Gough Island in the South Atlantic Ocean, to help plan the removal of mice. 

Keith Broome. Photo: Chris Bell.

Keith Broome on Gough Island

Last September, at the request of the Royal Society for the Protection of Birds (RSPB), I travelled to Cape Town to join a voyage to Gough Island to help develop the project to eradicate mice from the 6500 ha island.

The wild coast of Gough Island the most significant seabird island in the Atlantic.

The wild coast of Gough Island the most significant seabird island in the Atlantic

DOC has been long involved in the Gough mouse eradication project, following an offer in 2005 by the then Minister of Conservation to support the project with technical advice.

Accompanying me on this voyage was Peter Garden, a very experienced helicopter pilot based in Wanaka, who has flown several aerially applied rodent eradication projects in New Zealand and around the world.

Peter Garden on the deck  of Agulhas II. Gough Island in the background.

Peter Garden on the deck of Agulhas II. Gough Island in the background

The brief was to gather some first-hand knowledge of the island and to work with Peter to update the current draft operational plan.

The project has many parallels with our Antipodes mouse eradication project, so the experience was valuable in thinking through the planning issues and eradication design, as well as the logistical issues and options to address them.

Gough bunting—endemic to Gough Island.

Gough bunting—endemic to Gough Island

The impacts of mice on the Gough ecosystem is substantial, and their impact on the endemic endangered Tristan albatross is catastrophic, with some study sites losing 9 of every 10 nests to mice.

Mouse predation is widespread among other seabird species as well, with records of attacks on yellow-nosed albatross, Sooty albatross and Atlantic petrel.

Yellow-nosed albatross on its nest.

Yellow-nosed albatross on its nest

I found that the island biosecurity system operating for Gough was good and I picked up a few tips.

Tristan albatross chick. Mouse attacks on younger  birds kill about 70% per year

Tristan albatross chick. Mouse attacks on younger birds kill about 70% per year

For example, they use sticky traps with ultraviolet lights to attract flying insects. These are throughout the cargo store and on board the ship that sails to the island. The ship also has a policy of no food consumed outside the dining and lounge areas.

Spending time with Peter was extremely helpful in learning more about how helicopters operate in eradication operations and how pilots view various issues.

Seeing the aerial weather station resupply really brought home to me the incredible skill and efficiency with which Kiwi pilots work and how so much of this comes from our unique situation of having a large agricultural aviation industry, which supports the sort of flying skills we need in DOC work.

Keith at Tarn Moss, Gough Island.

Keith at Tarn Moss, Gough Island

On the whole, it was a great experience and great project to contribute to. I made a number of new contacts and grew my knowledge of island management and pest eradication.

Battle for our Birds - Beech mast 2014Recently we posted about the problem of increased predator numbers this year, due to predicted heavy beech forest seedfall. We also discussed what this could mean for our endangered native wildlife.

Today, we’re going to have a closer look at what we’re going to do about it…

How does DOC plan to protect at risk populations?

DOC routinely uses traps and other ground based techniques such as bait stations to control rats, stoats and possums. Traps and bait stations will continue to play a significant role in protecting threatened populations such as whio/blue duck in Tongariro, mōhua in the Eglinton valley and kiwi in the West Coast.

Whio. Photo: Matt Binns | CC BY 2.0

Our whio are nationally vulnerable, with less than 3,000 remaining

However research has shown that rapidly rising rat numbers produced by mast conditions can overwhelm trap networks. Ground based control on its own does not protect threatened bird and bat populations from these predator explosions.

The study of pest control techniques during two localised rat plagues in 2006 and 2009 through DOC’s Operation Ark multi-species protection programme showed that aerial 1080 treatment knocked down rat plagues to near zero levels where ground based methods were not effective on their own.

DOC is prepared to significantly expand its aerial 1080 operations in South Island beech forests in 2014/15 to respond to rising predator numbers.

Beech forest. Photo: Shannan Mortimer (CC BY-NC-SA 2.0).

South Island beech forest

How effective is 1080 in countering these predator threats?

Permanently eliminating rats and stoats is not currently feasible but research during past mast events has shown aerial 1080 to be the most cost effective tool for quickly knocking down predators over large areas and in difficult terrain.

Aerial 1080 has been shown to suppress rodent plagues to near zero density levels for up to five months. Tracking results indicated it can also kill more than 95% of stoats through secondary poisoning.

For example, aerial 1080 used in the Dart Valley in Fiordland during the rat plague in 2006 resulted in 80% of mōhua surviving whereas in uncontrolled areas only 10% survived.

At Ōkārito on the West Coast aerial 1080 timed to target rats after a beech mast in 2011 doubled the nesting success of kea. Kea pairs in the treated area produced about four chicks each whereas those in the untreated area produced only one due to stoats and possums preying on nests.

Young kea. Photo: Brent Barrett | CC BY-NC-ND 2.0

Aerial 1080 timed to target rats after a beech mast in 2011 doubled the nesting success of kea

As well as being fast and effective over wide areas, aerial 1080 operations cost approximately a third the cost of most ground based alternatives.

Get more information about the use of 1080 for pest control.

How much land managed by DOC is currently treated with aerial 1080?

Pest control cycles vary but over the past five years DOC has treated an average of about 140,000 hectares with aerial 1080 specifically to protect forest ecosystems and native species. This represents about 2% of the 8.7 million hectares of public conservation land which is managed by DOC.

TBfree New Zealand also carries out aerial 1080 operations over an approximate 300,000 additional hectares of public conservation land to protect dairy herds from possums infected with bovine tuberculosis.

Together these combined aerial 1080 programmes cover about 440,000 hectares or approximately about 5% of all public conservation land managed by DOC.

Giant snails/Powelliphanta. Photo: Kathryn and Stefan Marks | CC BY-NC-ND 2.0.

The Battle for our Birds doesn’t stop at protecting our birds, but other species such as our giant snails/Powelliphanta, which are among our most threatened invertebrates

How much more land is DOC preparing to treat with aerial 1080 as part of its Battle for our Birds beech mast response?

The exact scale of DOC’s aerial 1080 programme in the coming year will depend on whether predator populations reach levels which trigger a response but, if required, DOC is ready to increase its aerial 1080 protection in the South Island by about 500,000 hectares.

This together with TBfree New Zealand’s planned programme would result in a total of about a million hectares of public conservation land being treated with aerial 1080 in 2014/15 – about 12% of the land managed by DOC.

To increase its on-going protection for native species DOC is also committed to increasing its aerial 1080 programme by about 50,000 hectares a year for five years. This means DOC itself will be supporting the 2014 beech mast response by routinely treating about 400,000 hectares of public conservation with 1080 by 2019.

What is this expanded programme expected to cost and how will DOC pay for it?

This new Battle for our Birds programme is expected to cost about $21 million over five years. It is a priority project for DOC and will be funded out of the Department’s existing budget using efficiencies gained from improved pest control techniques and co-ordination of operations.