Global warming may be one of the reasons behind the recent appearance of football-sized, orange-toothed aquatic rodents in the Skagit River Valley of northwestern Washington.

Nutria, beaver-like creatures native to South America, are notorious for destroying flood-control levees and chewing through wetlands in the Southeastern United States. Fur entrepreneurs brought them to this country in the late 19th century, and although the pelt industry shriveled up, escaped nutria now thrive in 15 states, including Oregon and Washington. Each year, females can bear two litters of up to twelve kits each, so the animals have swiftly outpaced efforts to control them.

In Washington, populations have been checked until now by cool temperatures and limited wetlands, says Pamela Meacham of the state’s Department of Fish and Wildlife. But the species’ appearance in the Skagit River Valley earlier this year has Meacham worried that mild winters and rising temperatures are allowing it to move north, along with other warm-weather invasive species.

Across the Pacific Northwest, winter temperatures are rising faster than the global average. Washington state climatologist Philip Mote notes that the valley’s shrinking snowpack and changing river flow patterns also suggest a local warming trend.

Skagit Valley residents and farmers are determined to kill off the nutria before they gain a toehold; they fear that without quick action, the burrowing animals could wreak havoc on the dikes that keep low-lying land from flooding. A short-lived government eradication program has run out of money, but The Nature Conservancy, a nonprofit, has offered a $10,000 challenge grant towards a goal of $30,000 for additional trapping.