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Doubling Down on Dr Morgan’s Dangerous Idea

January 25, 2013

Recently, the economist Dr Gareth Morgan launched a campaign to reduce the number of cats in New Zealand, and to reduce the ecological damage by the ones that are here. He’s encouraging people to desex their pet cats, put a bell on them, keep them indoors wherever possible, and consider not getting a new cat when their current cat dies.

As a conservation ecologist, these suggestions all struck me as sensible, and even on the mild end of the spectrum. And yet, the campaign has been criticised as being ‘extreme’ and ‘radical’ in the mainstream press [read the comments especially!].

I fully support Dr Morgan’s campaign, but really, it is pretty mild stuff. New Zealand is a world leader [pdf] in controlling or eliminating invasive mammals – we can do better than merely slightly reducing the number and impacts of cats in our cities. But we need a real plan – the sort of plan that can be called ‘extreme’ with some serious justification. Here’s the rough outline of a really, truly extreme idea, that we just *might* be able to pull off:

The Plan: Total eradication of all invasive non-commercial mammals (cats, rats, mice, possums, rabbits, hares, stoats, weasels, ferrets, hedgehogs, wallaby) from mainland New Zealand.

Divide the country into large, but manageable, eradication areas (blocks) by building predator-proof fencing, like that seen at Tawharanui, across the country. Phase out cats, mice and rats as legal pets, allowing current pets to die of natural causes but not allowing people to get new ones.

In the meantime, while people’s pets are slowly dying of old age, get people used to the idea of mammal quarantine: start by instituting rat-proofing on Interislander ferries similar to that required for commercial boats servicing predator-free Hauraki Gulf islands like Tiritiri Matangi. Institute the same levels of mammal control at airports. Wherever possible, set up intense rat and mouse-control in businesses that send things between blocks to minimise the number of pests that will be accidentally spread. Get the public used to invasive-mammal containment. Set up 0800 numbers for people to call if they spot a rat or mouse after the eradication has happened in their area, so that any stragglers or tough colonies can be dealt with effectively. Get monitoring protocols set up, so that any re-invasion can be spotted quickly and dealt with before it becomes a problem.

Start the eradication at the bottom of the South Island, and work Northwards, block by block. Use established methods for eradication, essentially following the Pacific Invasives Initiative guidelines for each block: aerial 1080 or brodifacoum [pdf], coupled with dog teams and intensive monitoring until we are completely certain that each block is invasive-mammal free. Repeat until New Zealand is invasive-mammal free. On an ongoing basis, monitor the ports and airports to reduce the risk of future incursions by these pests, and keep crews trained to respond quickly to any new incursions in pest-free areas, like is already done at predator-free sanctuaries.

This sounds pretty extreme, but consider: invasive mammal eradications from islands for conservation purposes only began in earnest in the early 1980s. Since then, we have gone from eradicating invasive mammals from islands a few tens of hectares in size to eradicating mammals from islands thousands of hectares, even some tens of thousands or hundreds of thousands of hectares, in size. New Zealand has led the way [pdf] in developing the technologies to make that possible. If anyone can do this, we can. We’ve developed those techniques, in large part, because our native species are more vulnerable to introduced mammal pests than the native species of other countries. If anyone should do this, we should.

There are, of course, some side advantages. Not only is there an ecological advantage of having enhanced our native wildlife, which is awesome (can you imagine kaka making it back into our cities?), not to mention rather useful to our tourism sector. There are also advantages to just not having to deal with rats any more – no more spending money on their ongoing control (although, admittedly, some ongoing cost of monitoring). No more crop losses to rodent damage. No more rodent-chewed wires causing housefires, or rodents chewing on precious national documents. There are advantages to not having cats around – no more being woken up by neighbourhood feral cats yowling at three in the morning. No more toxoplasmosis. Rabbits cause costly damage to pasture, possums are expensively controlled to reduce the risk that they’ll transfer TB to cattle. We could seriously do without invasive mammals – helping our native wildlife is just the tip of the iceberg.

And as extreme as it sounds, it’s not so extreme that people aren’t already heading that way. Recently, for instance, people have begun looking at the possibility of eradicating rats, cats and possums from Stewart Island and Great Barrier Island, and have concluded that such eradications are technically feasible, if enough community support can be raised. Stewart Island is 168,000 hectares, with a permanent human settlement of around 400 people. If we were to divide the South Island up into blocks the size of Stewart Island, we would need only 90 blocks. It may be extreme, but it certainly isn’t unimaginable. You might even say it is the next sensible thing to do. And, if you did say that, you would be thinking like a conservation biologist at the cutting edge of conservation biology. Nice.


From → Science

  1. Bryce Coulter permalink

    This is a really good idea, also more jobs would have to be created to do this which would help New Zealand’s ecomony.

  2. Any particular reason why you’ve left dogs out of this?

    • Only that they’re often used commercially, and would probably have to be used in the eradication effort itself. From a pure ecological standpoint, their eradication outside of specialist roles makes sense too.

      • Dogs are only really an issue for ground nesting birds. Making it compulsory for all dogs to undergo an aversion therapy course (like the kiwi ones) every year would eliminate this problem. The kiwi aversion courses have a 95% success rate so the remaining 5% could be eliminated if they failed to pass a subsequent course. The courses could be beefed up a bit to make them more comprehensive. The kiwi aversion courses are very cheap. I think less than $20 per dog. Every dog owner should put their dog through it regardless of size, age or locality.

        Work dogs (like pig hunting dogs) are generally trained by their owners against non-target animals because it makes them focus on their work better. My own dog is stock (cattle, sheep, horse) proof, rabbit proof, cat proof and bird proof (native and domestic) because I invested the time in her at a young age. She is also strangely enough domestic pig proof despite the fact she was a pig hunting dog – not sure how much I would trust her with this but we have lived in places with domestic pigs and she hasn’t touched them and we had a pet pig that she used to hang out and sleep with.

        This is the difference between cats and dogs. Dogs are much more trainable than cats. You can train cats to some degree but you can’t trust them to remember this training all the time especially when they are on their own.

        Cats also have a massive impact on insects and reptiles.

      • I still have some reservations about dogs. I have definitely seen them used for conservation purposes in a way that only a dog could have been used. I have also seen them used commercially in ways that only dogs can be used.

        In every practical sense, I would be thrilled if NZ required (and enforced, and provided incentives for people to stick to) ground-bird avoidance training for all dogs.

        But that would not solve the problems with feral dogs and unregistered dogs, nor would it help with the 13% of dogs that forget their kiwi aversion training during the first year (source:

        I still think the hypothetical best-case-scenario for conservation in NZ involves no dogs other than those directly involved in conservation work, whose direct conservation benefit outweighs the cost of the 13% who slip through the training cracks. But it sounds like the training would be a *huge* step in the right direction, if it could be effectively applied to all dogs in NZ.

  3. I guess what I am trying to say is that you just have to pick your battles. Increasing the amount of no dog zones in critical areas could be an idea but the complete eradication of dogs in NZ is just a fight I don’t believe you can ever win.
    Even only keeping those used for conservation is also unrealistic – how do you tell a farmer that he is not allowed to own sheepdogs when they are his only tool for rounding up sheep in rough terrain? What about guide dogs?

    The 13% that revert in the first year could be decreased if:
    1) dogs are put into the courses earlier on in life (i.e. puppy training)
    2) the courses are more comprehensive including a longer initial training period with a greater variety of species including farm animals. If they learn that they are not allowed to attack any other animal it gets rid of any grey areas.
    3) refresher courses every year are mandatory
    4) owners are trained in control of their pets

    Working towards NZ having a completely controlled dog population is a more realistic and achievable goal. Compulsory aversion therapy training as well as more stringent control of the dog laws already in place needs to be performed. Owners should be screened to ensure they have adequate fencing. Repeat offenders of wandering dogs have their dogs removed from them with no third chances. Farmers are screened regularly to check numbers and status of dogs. Any feral dogs found are euthanised unless they stand a good chance of being rehomed with all the above measures. No faffing about with putting them through expensive courses to make sure they are suitable for rehoming – plenty of purebreds wouldn’t pass those courses.

    The main reason people don’t register their dogs is that it costs several hundred dollars a year to do so. Making dog registration cheaper would go a long way towards getting all the dogs into the system.
    It might never be perfect but it could be a lot better.

    On another note a much more winnable battle to fight would be the complete eradication of feral herbivores which destroy the base of your food chain. So deer, goats, mongrel Kaimanawa inbred ugly horses (all of them), etc.
    This combined with eradication of mustelids, rodents and cats would go a lot further than removing the few dogs that are actually causing a problem.

    • Yes, I think you’re right. I do have to pick my battles, which is why I originally excluded commercial animals from the list of things that would be exterminated: although the dairy cattle population in NZ does untold damage to our lowland river quality, I don’t think it’d be possible to sell the idea of cattle eradication to the public. Same deal with leaving dogs out of the list in the original post.

      The dog-registration issues are really interesting, though. I think a dog-controlled society, where all dogs are registered, desexed, and given bird aversion training, might have to be a society where people do not, in general, have the right to own dogs, but can apply for exemptions for commercial or conservation reasons: where dogs are seen as an investment, rather than a pet, and dogs are seen as ‘high-cost, high-value’ animals. The dog supply would probably have to be controlled – a small number of regulated breeders who supply only desexed animals to dog users, to prevent the problems associated with feral and unregistered dogs.

      If people can breed their own dogs, there’s an incentive to keep registration and required-training costs low (to encourage people to register instead of keeping their dogs off-grid) which means that there’s going to have to be cheaper (and probably less effective) training and control.

  4. I just meant the feral (wild) cattle population not the farmed population. In addition to feral deer, horses, goats, etc. In other words – all herbivorous farm animals that have escaped confinement. There are people in Northland who hunt wild cattle and round them up to send to the works. I think this is a purely ‘for profit’ activity and not environmental though.

    I agree about the cattle and waterways issue though. This is an issue that goes hand in hand with a lack of riparian vegetation on farmland and other areas.
    Fencing of riparian margins combined with vegetation is something that I thought all farmers were meant to do. It doesn’t appear to be the case though in most areas. I really should do my research and find out what the legal requirements of farmers are I suppose.

  5. In that case, yeah. But if there’s still a large farmed population of cows, deer, goats, horses, etc. then there are always going to be escapees, so the most you could go for long-term is control rather than eradication.

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