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Why eradicating invasive mice on the Farallon Islands is probably not a problem

May 18, 2014

Oh, dear.

I’ve just been directed towards a piece on the HuffPo, titled ‘The Farallon Islands, USFWS, and Island Conservation’s Tax-free Government Contracts‘, which gets riled up about New Zealand’s habit of eradicating introduced predators from offshore islands, and especially about the fact that our technology is now spreading to the US of A. It features juicy little tidbits like:

“This $1.3 million dollar (at a minimum) federal contract with Island Conservation targets non-native mice; however, the aerial broadcasting of loose rat poison pellets from helicopters over an island wildlife refuge will result in thousands of protected, wild animals being poisoned as “by-kill” or “collateral damage.” ”

“Lurking in the background is usually New Zealand’s Department of Conservation and their Island Eradication Advisory Service Group selling a variety of consulting services, including the bait and helicopter pilots necessary. Yes, the government of New Zealand is in the business of manufacturing Brodifacoum, 1080, and other horrific poisons via this factory, known as a State Owned Enterprise, which is a private business that the government owns, and profits from.”

“The practice of using helicopters to carry out poison drops (be it brodifacoum or 1080) is only done by the government of New Zealand. No other country in the world engages in this macabre practice that is driven by a business model that demands that an invasive species “crisis” be manufactured whenever money runs low.”

“No independent, third party auditor monitors the full ecosystem impacts of applying unprecedented volumes of one of the most deadly pesticides to wildlife since DDT, or confirms any of the claims of success made in press releases.”


“The risk for contamination of the Farallon food chain and long term epigenetic impacts to the entire ecosystem have been overlooked and dismissed by USFWS, Island Conservation, and Point Blue Conservation Science.”

Spoiler alert: no.

Tiritiri Matangi (foreground) and Little Barrier Island (background): secretly ravaged by human greed?


If someone were to take this piece of journalism seriously, they’d end up thinking that the New Zealand Government had conned its taxpayers into paying to set up a State Owned Enterprise that produces a poison-bait that the New Zealand Government is the sole customer for, that the Government then buys using taxpayer funding, resulting in the sorts of obscene profits to the Government that are liable to distort parliamentary process and cause all manner of corruption. The big loser in this story is the wildlife, who are slaughtered willy-nilly to line these corrupt bastards’ pockets.

On the face of it, this already seems pretty unlikely. After all, New Zealand is pretty routinely ranked amongst the world’s least corrupt democracies (we’ll beat you yet, Denmark!), so a blatant swindle like this would be quite an aberration from the rest of our behaviour. Then there is the matter of how this equation, which is claimed to describe the New Zealand Government’s behaviour, makes any sense:

“Pay to set up State Owned Enterprise”
+     “Pay for the bait the State Owned Enterprise produces”
+    “Pay for the staff to apply the bait to the landscape”
=     “Profit!”

In the journalist’s defence, I can see where they went wrong. New Zealand has, after all, developed techniques to exterminate small (and not-so-small) furry mammals from large tracts of land. We do, indeed, use aerially-boradcast brodifacoum and 1080 poison-baits to do it. Yes, by-kill is a potential issue. But they seem to have missed a few rather crucial points.

First up, the reason we eradicate invasive species isn’t for profit. Profit for the country might come later, because the ecological restoration associated with eradicating introduced species attracts a whole lot of tourists, but the people who sell poison-bait aren’t the same people who sell tourism packages. We eradicate invasive species because the ecological benefits of eradicating invasive species are huge, and incredibly well-documented. The IUCN (famous for producing the Red List of Endangered Species, amongst other things) lists invasive species as the second most significant cause of extinction worldwide, behind only habitat loss. The damage caused by invasive species is ongoing, with more species being driven extinct by them on a yearly basis. If we remove the invasive species, that threat disappears – and the evidence we have shows that the ecological recoveries caused by removing invasive species are dramatic.

Secondly, if this is a con, then it’s the only con in the history of the Universe where the primary method is to tell everyone everything that is going on, at every step of the process. In government-funded projects in a country as small as New Zealand, there are very few areas of spending that escape the notice of the public. The people running the programmes know that public approval of the process is vital, and that if the public couldn’t see the massive benefits, it would be all to easy to believe that aerial deployment of predator baits was unjustified or too costly. So the aggressively-followed regimen has been: Make it accessible. Publish the data. Make damned sure that everyone can see what happens.

So, if you want to visit one of the sites where we have eradicated invasive species, here’s how you do it:

1) Catch a plane into Auckland, New Zealand’s most populous city.
2) Catch the AirBus (NZ$16 one way; $28 return) to the central city. Get off at the Downtown Ferry Terminal.
3) Walk to Pier 4, and book a ticket to Tiritiri Matangi Island with 360 Discovery Cruises (Adults $69 return; family passes available).
4) Get on the boat. The trip will take about an hour. Don’t drink the coffee; the tea is much better.

If you happen to be in the capital, Wellington, you can visit Matiu/Somes Island instead of Tiritiri Matangi. The process is basically the same, but the ferry tickets are cheaper (adults $23 return) because the island is closer to the central ferry building. Or you can drive to Paraparaumu (about an hour out of the capital) and catch a ferry to Kapiti Island (adults $95).

If you’d like to visit a site during a 1080 or brodifacoum deployment, you can generally do that too. Eradication of invasive species isn’t always feasible, so many popular hiking areas receive periodic predator-control using the same methods as we use for eradication. Signs informing people of the baits’ existence are a familiar greeting to many of these areas – especially just before the breeding period, to knock back predators and give our endangered species the best chance of breeding successfully. Generally the helicopter pilots are good enough to prevent any baits from landing on hiking tracks, but the signs give contact numbers in case any are found on-track, tell people how to identify baits, ask people not to touch any baits that they do see or eat any animals from the area, and especially warn people that dogs should not be brought into the area while baits are present.

In addition to making predator-controlled sites as open as possible to the public, the New Zealand authorities have been very careful to make the scientific data available to the public. So, if you want to know what the likelihood of landscape contamination is, that’s fair enough. The research has been done by a variety of research organisations, including our leading universities and crown research organisations. If you’d like to see the breakdown profile in water for 1080 or brodifacoum, that’s all freely available. If you’d like to see data on the effects of brodifacoum application on our native scavenger populations (which you might expect to scavenge poisoned rats, and thereby be poisoned themselves), you can find a paper on that. If you’d like to see a worst-case scenario for 1080 absorption into plants, or popular food species, or its distribution through the food web, that’s all available. If you’d like to see the original research papers, many of those are also available – though some may require a University library membership.

The upshot of this research is that both 1080 and brodifacoum biodegrade on a timescale of days to months, depending on weather conditions, so uneaten baits don’t accumulate to any substantial degree in the environment. Brodifacoum persists for longer in tissues (especially liver tissue) than on the forest floor, so hunters are advised to discard offal from wild meat shot in areas where brodifacoum has been applied, and active research is underway to find alternatives to brodifacoum to avoid any possibility of bio-accumulation.  There are non-target species that are at risk of being poisoned during these operations. We’ve managed to hugely cut down the bykill rate by doing things like dyeing baits so that they don’t look like food to non-target species and researching the effects of alternative baits on target species behaviour. We’re now at the point where the non-target secondary poisoning rate is detectable, but dramatically swamped by the increase in breeding success associated with predator removal.

A final word: the HuffPo piece ends with a video from the ‘censored’ Graf Boys, who have some objections to the use of 1080. They’re not censored, of course – the keen observer will notice that the Graf Boys have a YouTube channel that no-one is asking them to take down. If anyone actually tried to censor them, that would justifiably cause public outcry. If we were the sort of nation that practised censorship on a large scale, we probably wouldn’t rank amongst the world’s least corrupt democracies.

In reality, the anti-1080 lobby is a consistent, but small, voting bloc comprised mainly of hunters. They are represented in Parliament occasionally. For instance, back in 2006 an anti-1080 lobby group made a deal with a small religious conservative party called United Future (0.6% of the popular vote at the last election; greatest electoral return 6.7% of the popular vote in 2002), but the anti-1080 lobby split from United Future soon after on the basis that they supported the separation of church and state, whereas United Future would like to see Christian doctrine officially supported in New Zealand law. At the moment, the anti-1080 lobby’s greatest support in Parliament seems to be New Zealand First (6.59% of the popular vote at the last election), who quietly list opposition to 1080 as one of their official party stances. The incumbent National-led (47.31% of the popular vote at the last election) government, while dramatically decreasing DoC funding generally, have increased funding for 1080 specifically. Labour (the major opposition party, 27.48% of the popular vote at the last election), and the Green party (11.1% at the last election) both endorse 1080 use, although the Greens specifically endorse actively looking for alternatives.

h/t also to Peter Pyle, for his assessments of the specific case of the Farallon Islands.

[edit: the title was “Why eradicating predators on the Farallon Islands is probably not a problem”, but this lacked clarity. Mice are important predators in island ecosystems, especially of invertebrates and herpetiles. I have made the change to avoid any potential confusion with Burrowing Owls]


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