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Know the West

Snail's trail leads to Yellowstone

  Wolves and exotic lake trout aren't the only new denizens of Yellowstone National Park. New Zealand mudsnails, as tiny as BBs and as prolific as fruit flies, have rapidly spread throughout the park's upper Madison River.

Although trout eat the snails, they pass through the fish undigested and alive, and reproduce so quickly that they can displace what the fish eat: larvae of stoneflies, caddisflies and other insects. "They short-circuit the food chain," Daniel Gustafson, a research scientist at Montana State University, told the Billings Gazette.

Scientists believe the mudsnails first reached North America in shipments of trout released into the Snake River in the 1980s. Besides the Madison River, they also live in a stretch of the Snake River from Pocatello to Mountain Home, Idaho, where they often clog irrigation ditches. Snails do poorly in cold water, but both rivers are warmed by hot springs.

Yellowstone's chief scientist, John Varley, says Park officials haven't had time or money to study the invasion, "and I don't know when we will." - Mark Matthews