Yellowstone Under Snail Siege

The invasive New Zealand mud snail threatens local fish populations in national parks

I always thought Canada would be the first anglophone country to try and invade us—they've always been just so jealous of our privatized health care, higher crime rates, and tighter marijuana policies. But I was wrong: Seemingly docile New Zealand has made the first assault on our shores, in the form of an invasive mud snail that threatens native fish. Say it ain't so, Frodo!

Those hardy mud snails likely snuck into the States by hitching a ride on the felt soles of fly fishing pants to Hagerman, Idaho sometime in the 80s. They've now infested Yellowstone and have spread as far as California, where they threaten to harm local ecosystems and fish by devouring the food source before trout and other species can get to it. They're so effective at out-eating the competition that In some rivers, 95 percent of the invertebrates biomass belongs to NZ mud snails.

To prevent spread, fly fishermen are strongly encouraged to wear rubber-soled waders instead of traditional felt, and hikers should inspect boots, pets, and just about anything after water crossings. Here's friendly Ranger Gary explaining the deal:



I should've expected that New Zealand would attack us when we least expect it, using their disarming Kiwi accent and good-natured charm. And I bet Canada helped.

—Ted Alvarez

New Zealand Mud Snail in Western U.S. (Montana State)

Via The Goat