Rat Island (Hawadax Island) Norway Rat Eradication — A Cautionary Case in Non-Target Mortality (USA)

Rat (Hawadax) Island in the Aleutians hosted a Norway rat population dating from an 18th-century shipwreck that had devastated native seabird colonies for over 200 years.

In September-October 2008, the U.S. Fish and Wildlife Service (Alaska Maritime National Wildlife Refuge), The Nature Conservancy and the nonprofit Island Conservation aerially broadcast roughly 46 metric tons of 25-ppm brodifacoum cereal bait over the 2,780-hectare (6,861-acre) island to eradicate the rats. Reported project cost is given as USD 2.5 million by Hakai Magazine and USD 3.5 million by the Anchorage Daily News — the discrepancy is unresolved in public reporting.

An unusually early snowfall covered and preserved the bait pellets far longer than models predicted, so gulls fed directly on bait and eagles then fed on poisoned rats and gulls instead of their normal autumn salmon diet. National Wildlife Health Center necropsies attributed an estimated 46 bald eagle and 320 glaucous-winged gull deaths (422 carcasses across roughly 25 species in total) to the operation — a toll USFWS itself called higher than expected. No rats were detected in 2009 surveys, and the island was declared rat-free by 2010. In May 2012 the U.S. Board on Geographic Names restored its Unangan/Aleut name, Hawadax Island. A peer-reviewed 2021 Scientific Reports (Nature) study found glaucous-winged gull nests rose from 5 (2008) to 27 (2013), Black Oystercatchers increased roughly 900% and gulls roughly 291% by 2019, and the rocky intertidal invertebrate community had shifted to resemble rat-free reference islands 11 years after eradication.

This practice is documented here as a cautionary case: the long-term ecological recovery is real and peer-reviewed, but it followed a serious, well-publicised non-target mortality event caused by a weather-driven planning miscalculation, illustrating the operational risk of aerial rodenticide campaigns even when the underlying eradication succeeds.