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
This article appeared in the print edition of the magazine with the headline Snail’s trail leads to Yellowstone.
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