I Know An Old Lady Who Swallowed A Fly | Vol. 3 / No. 27.2

Don’t throw it back! Take it and all its friends! | Photo: David Keep, CC BY 2.0

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There’s an old song made “famous” by Burl Ives that I grew up listening to and — because Canada — watching a strangely-dated animation of instead of commercial breaks (three cheers for the National Film Board!). If you’re not familiar with the song, it begins with the words “I know and old lady who swallowed a fly, I don’t know why she swallowed that fly… perhaps she’ll die.” With each cumulative verse, she swallows something to catch the last thing she swallowed. By the end she’s swallowed a spider to catch the fly, a bird to catch the spider, a cat to catch the bird, a dog to catch the cat (and so on) until eventually she dies from swallowing a horse.

Being me, this is precisely what I thought of when I heard of Australia’s latest attempt to patch up its perennially chaotic ecosystem, introducing a species-specific herpes virus to kill all the invasive carp.

Basically, Australia has this problem with invasive species. We all have problems with invasive species, of course (hello kudzu!), but Australia’s especially vulnerable because its island status has left it less-practiced at dealing with change. This is what happened when in 1935 sugar producers introduced the foreign Cane Toad to try to control the native Cane Beetle (which was eating their sugarcane). The toads are both voracious feeders and poisonous to eat, so they’ve spread prodigiously and are greatly disturbing Australia’s ecosystems.

There are lists of invasive species introduced to Australia — rabbits, red foxes, camels, goats, cats, pigs, etc. — and there have been many attempts to control them by many means. Poisoned bait traps for the foxes haven’t worked terribly well. They tried basically everything for the rabbits — including a massive rabbit-proof fence that didn’t work. Helicopter culls are the go-to for the camels and goats, apparently. (On a side note, look up “judas goats” for a sad tale of trying to correct an ecological screw-up in the Galapagos).

In 1950, they tried using myxoma virus to fight the rabbits. And while it did reduce the population — from 600 million down to “just” 100 million — by the 1990s they were back into the 200-300 million range. They’ve since released another virus, calcivirus, but that was actually by accident — it escaped from a quarantined facility they were testing it in. From the release they learned that there was already a non-fatal version of calcivirus in the country’s cooler regions that was giving the rabbits some protection, though it seems to work better in the warmer areas.

Enter the carp. People have been releasing carp into the wild Australia — accidentally and on purpose — for years. If you don’t know, carp are great for sport fishing, and some people like to eat them (I don’t — among other things, they’re really bony). They also reproduce prodigiously, and eat pretty much anything they can fit in their mouths. You’ve probably met some carp already — goldfish and koi are both kinds of carp — and of course some of the accidental releases come from escaped or released pets. But they’re not great for the environment, and, like the rabbits, the Australian government would like to get rid of them.

So they’re going ahead with a plan their science minister is dubbing “carp-ageddon,” releasing a carp-specific herpes virus with the hopes of creating a massive die-off. They’ve been researching it for six or seven years just to make sure it won’t hurt any humans and also to plan what to do with the estimated 500,000 to 2,000,000 tons of dead carp they’re expecting to have to haul out of the rivers.

So I’m not really worried about the humans. Like releasing inactive bacteria on the west coast of the US to control the Gypsy Moth population, I think it’s an innovative solution that poses minimal risk. What I’m thinking, though, is that I’m not sure how well this is going to work in the long run. Oh, I think just like the rabbits it’ll work for a while. But as we all know, “life… uh… finds a way.” So what I anticipate we’ll get by using the virus in a wild setting is a population of carp that are increasingly immune to herpes, and whose numbers will eventually climb again.

The lesson isn’t that we shouldn’t try to maintain balance in our ecosystems. We should, and they should be applauded for at least trying. Rather, the lesson is the same one as that old Burl Ives song: once lost, balance in an ecosystem is really really hard to get back.

In the meantime, anybody interested in some carp-based fertilizer? ABC News has more.

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