When Invasives Go Bad. Really Bad.

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Published on January 16th, 2009  |  Discuss This Article  

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This week, scientists at the Australian Antarctic Division published a paper in the Journal of Applied Ecology about invasive species, relating a story that boggles the mind.

Start with Macquarie Island, located between New Zealand and Antarctica, and the property of Tasmania. Its surface area is only about 128 square kilometers, so you really have to be careful steering GoogleEarth there: one cursor slip and you’ll splash down into the monotonous stretches of the Southern Ocean. (Try 54 deg 29′ 56.07″ S, 158 deg 56′ 16.68″ E to spy on the Research Station).

So here’s the story line. Macquarie Island was discovered by the Brits in 1810, who went gaga over the seals and penguins (which of course were “harvested” for the usual reasons). In exchange, the sailors gifted the island with rats and mice. Great….

Pretty soon, the introduced rodents started annoying the sailors, so then in 1818 they introduced cats. Great….

Oh, then because the sailors were hungry, in 1878 they introduced rabbits. Great, again….

Proceed to 1960 — apparently the sailors hadn’t been keeping up on their part of the deal because the rabbit population had exploded (what a surprise!) to 130,000 animals. That’s a lot of sailor food!

And all that sailor food was overgrazing the island. So next, in 1968, a rabbit flea was intentionally put on the island, and then 10 years later the Myxoma virus was introduced as a biocontrol. Deadly Myxomatosis was rapidly transmitted via the fleas, and the rabbit population plummeted from 130,000 to about 20,000. Ooh, that sounds like an improvement, doesn’t it?

Except for all those cats — about 2,500 of them. They had been filling in for the sailors by eating all the rabbit meat they could. But deprived of the rabbits, they switched to birdflesh. Remember all the penguins? So the bird populations started dropping.

Next to go, then, were the cats. During 1985 to 2000, the total kitty kill-count reached about 2,000 animals. OK, that hurt (especially if you were a cat), but again normalcy was being approached, right?

Well, no. You see, there will always be some survivors after a plague, and in this spirit the surviving rabbit population (remember the rabbits?) rebounded. And with no kitty cats eating them, the rabbit population once again exceeded 100,000 animals.

That brings us up to today. The rabbits are eating everything. Erosion is rampant. An erosion-abetted landslide slammed into a penguin rookery. Once again, things are screwed up. Koyaanisqatsi!

In response to all this, the government of Australia has committed AU$24 million to simultaneously eliminate the rabbits AND the mice AND the rats. This will be the largest eradication program on an island ever attempted. (Against non-native species that is — humans have already demonstrated skill at eradicating native island species!)

There are two lessons in this:

  1. It is vastly easier to screw up than it is to do right.
  2. OK, there’s really only one lesson.

(Image: Royal Penguins on Macqueria Island. Credit: M. Murphy under a Creative Commons license.)

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Comments: When Invasives Go Bad. Really Bad.

  •  Comment from sophie

    yes. Really, just – yes. Not a lot else to say to that… It’s a story that I knew, and if I hadn;t, I wouldn;t have been surprised. (while I’m here, does “Captain MacAdam’s Rat” mean anything to you? I think I may have the name wrong because I have never been able to find confirmation of it anywhere. I might have swallowed it whole from a Kurt Vonnegut book, you never know.)
    Anyway – I got here from your lovely site of carnivorous plants, which is fantastic; being able to laugh out loud when sat by yourself at a computer reading a FAQ on Venus Flytraps is a good experience. Thank you for that, I really enjoyed it ;)

  •  Comment from Cassie

    You should hear about New Zealand itself (I heard this while on holiday there). On the South Island, the only mammal to be found was the Sea Lion, which was harvested for their fur and blubber by white people. The seals then became very hard to find, so they brought in a whole heap of rabbits in for their fur instead, and let them loose. Then fur went out of fashion not much later. To get rid of the rabbits, the stoat was introduced, which ignored the rabbits to enjoy the large variety of native birds. (Many of New Zealand’s birds are flightless because there was no danger on the ground.) To get rid of stoats, they introduced cats and dogs, which ignored the stoats and the rabbits to eat the birds…..

    They didn’t use their brains.

    Similar story in Australia, the Cane Toad was brought in to eat the Cane Beetle, which was eating out cane sugar crops. Cane Toads don’t eat Came Beetles, they only share a name. Needless to say, we now have a massive Cane Toad problems! No-one used their brains here either.

    How very, very sad.

    I hope they will think things through this time.

    (By the way, I love the picture.)

  •  Comment from Barry Rice

    Hey Cassie,

    I’m familiar with your tales of woe, and I’ve got a file cabinet full of other ones. The good news is that modern “biocontrol” (introducing yet other organisms to systems to combat existing ones) is now done much more carefully, usually using pathogens or exceedlingly host-specific invertebrates.

  •  Comment from Bird Advocate

    Thanks for the update, Barry. I’m hoping conservation issues are not forgotten in this financial crisis.

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