They Killed the Rats of 'Rat Island,' With Unexpected Results

Study finds the full ecosystem has fully recovered
By Kate Seamons,  Newser Staff
Posted Apr 11, 2021 1:31 PM CDT
They Killed the Rats of 'Rat Island,' With Unexpected Results
Hawadax Island (formerly Rat Island).   (US Fish and Wildlife Services)

The name "Rat Island" has persisted for decades, but it 2012 it was officially done away with, and for good reason. The rats are gone. Popular Science dives into how that came to be and what the longer-term results have been via a March study published in Nature Scientific Reports. Rat Island, or Hawadax Island as it is officially known, sits in the Aleutian Island chain off Alaska. It's thought that the rat infestation happened in the 1780s when a ship went down off its coast; the rats who managed to get ashore then populated the island. They had free rein until 2008, when the US Fish and Wildlife Service, the Nature Conservancy, and the nonprofit Island Conservation teamed up to get rid of them by scattering poison pellets on the island by helicopter. The rats are gone, but what's come back exceeded scientists' expectations.

"There are other things that these rats are doing that we hadn't necessarily thought of," says study co-author Dan Croll. The researchers had expected that birds—Black Oystercatchers and Glaucous-winged Gulls—would return without the rats as predators, and they did. But the return of the shorebirds meant there was now something to eat the sea stars, snails, and other invertebrates that pepper the island's rocky shores and in turn eat up all the kelp there. The kelp numbers ballooned. The study shows "how ecosystems can fully recover to their natural state in little more than a decade," per a press release. (Researchers determined what that "natural state" would have been by using data from other Aleutian Islands.) The study notes that few post-eradication studies of this nature have occurred, and that has scientists saying this one provides valuable guidance on what can be expected with future eradication efforts. (More scientific study stories.)

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