Invasive species are a major problem in our modern world. That’s because we’re generally happy with the way things are and less happy when some vagabonding drabcoat like a starling or a wild pig or even a smallish purple thistle moves in and starts carpeting the place. Also, frequently enough, the invaders got a lift over from us, and so we feel a lingering sense of guilt over the whole fiasco, at least those of us who haven’t made pots of money off not worrying about it.
And so it has gone with pigs, goats, cane toads, zebra mussels, nutria, rabbits, eucalyptus, kudzu, privet, tamarisk, all manner of ballast-water hitchhikers, brown tree snakes, lake trout, fire ants, house finches, leafy spurge, scotch broom, big jellyfish, uncomfortably large sea urchins. There’s even evidence we were carting fruit bats from island to island nearly a thousand years ago, for God’s sake.
And then of course there’s the original: the rat. The consummate invader has made mincemeat of island oddities ever since the first one dragged its creepy hairless tail off a sailing ship and started infiltrating nests of helpless birds (like the flightless kakapo, a New Zealand parrot the size of a toddler).
But today’s post isn’t about bad news. It isn’t about scurrilous rats with their insatiable appetite, their lust for expansion, their pyramid schemes and gleaming steel shrines to capitalism. It’s about community, faith, and grit. A small band of determined locals. And a shearwater.
Wedge-tailed shearwaters nest, among other places, on a 3-acre scrap of lava off O’ahu, Hawai’i, called Mokoli’i Island, in burrows that they somehow etch into the rocky soil. Unfortunately, rats have burrows pretty well figured out, and in the years 1999-2001 exactly one shearwater fledged from all the nests on the entire island.
Some University of Hawai’i researchers enlisted the help of concerned locals and started an e-rat-ication campaign in earnest. By May 2002, the team had scattered 354 blocks of poisoned bait, captured 18 rats, and could find no lingering ratty traces on Mokoli’i.
That same year the island’s shearwaters produced 126 young. For those of you who are impressed by large percentages, that’s a 37,800 percent increase (over the previous annual rate of 1/3 of a shearwater per year). The next year the tally went up another 50%, to 185. The researchers also noted, though a bit less scientifically, a definite increase in tidepool animals, native plants, and an endangered grass after the rats were removed.
There you are, some good news for a change. Now, if we could just get the rats out of the other 33.3442 billion acres (not counting Antarctica) of land on the planet.
Images: thanks to the University of Hawaii’s Project Ant (a whole other story in itself) and the USGS… and in other shearwater news: last week we found out that the sooty shearwater flies 40,000 miles in a lazy figure-8 around the Pacific every year, the longest animal migration yet documented.
It gets trickier when native rodents live alongside the invaders – no poison rat cakes allowed. On Anacapa, one of the Channel islands, conservation biologists figured the minimum number of deermice needed to repopulate the island, caught that many, then sprayed the place with rodenticide (by helicopter – yikes). Results? They wiped out the rats, murrelets hatched more murrelet-lets, auklets* returned to breed, and the deermice bounced right back.
hmmm… sounds like a freelance story developing? holler if you want sources. -S
*Anacapa, island of diminuitive birds.
Surprised that you didn’t mention the ineffective rat-tracking efforts of the european team of scientists that radio-tagged a rat and released it on an island, specifically to look in more detail at what makes rats so hard to eradicate (), also a newsbrief at MSN.com (). Good to hear a positive story in the news for once…
Susan – that’s a fantastic story…not one you are writing for New Scientist or anyone else, I gather? I’d love to find out sources…but will e-mail you directly in case you don’t check this comments section routinely. Charles – I hadn’t heard about the European rat chase but it sounds entertaining. Thanks, folks, for reading – H
[…] The Society for Conservation Biology keeps an eye out for cool science headlines on their new blog Journal Watch. Among recent offerings, eradicating rats from Ohinau, off New Zealand, let geckos bounce back much faster than researchers expected. Another reason to ask for your island without so much rat in it. […]