Idaho Researcher Finds Rare Giant Palouse Earthworm

The white, lily-scented denizen of the region’s fertile, deep soils reportedly can grow to 3 feet long. The rolling hills of the Palouse sprawl across an estimated 2 million acres of north central Idaho and southeastern Washington.

Sanchez-de Leon collected the 6-inch white worm from a remnant of Palouse prairie while studying earthworm populations and carbon dynamics in native prairie and retired farmland.

Northwest earthworm expert William M Fender-Westwind confirmed the identification of the worm Sanchez-de Leon found last May. His confirmation supported her initial identification and another by earthworm experts gathered for a workshop in her native Puerto Rico in November.

“This is exciting,” said James B. “Ding” Johnson, UI Plant, Soil and Entomological Sciences Department head. “By earthworm standards, they’re pretty cool.”

“It’s good news that this rare and interesting species is still with us,” Johnson said. He and graduate student Paul Johnson are believed to be the last scientists to document a sighting of the worm.

In 1988, they found several worms in a forest clearing on nearby Moscow Mountain while rolling back moss in search of the pill beetles he studied. They sent two specimens to Portland, Ore.-based Fender-Westwind for confirmation.

Early observers reported the giant Palouse earthworms could grow 2- to 3 feet long, big but modest compared to relatives from Australia that can reach 10 feet long.

Sanchez-de Leon discovered the worm last spring while digging the last of five pits in the Washington State University’s Smoot Hill Ecological Preserve near Palouse, Wash.

To collect samples, she dug five small pits, each about 10 inches square and 12 inches deep. While digging the day’s last pit, she noticed the flash of white in soil about 4 inches deep – and came up with part of the worm. Another shovelful held the rest.

“I noticed it immediately,” she said. “It’s very white and the anterior part is pink near the mouth.” Two UI environmental science students, Katherine Smetak and Juan F. Villa-Romero, joined her on the collecting trip.

Sanchez-de Leon is studying at the University of Idaho through the National Science Foundation’s Integrative Graduate Education and Research Traineeship program. As part of the joint program with Costa Rica’s Tropical Agricultural Research and Higher Education Center, she studied earthworm abundance in a coffee plantation during a summer internship there.

Although early reports say the worms have a lily-like scent when handled, neither Johnson nor Sanchez recalled detecting it.

Jodi Johnson-Maynard, UI assistant professor of soil and water management, said relocating the giant Palouse earthworm may offer another opportunity to learn more about its behavior and ecology.

Scientists suspect more than a century of intensive cultivation of the Palouse for wheat and other crops triggered the white worm’s rarity. Johnson-Maynard said another possibility is that the worm was always rare.

The giant Palouse earthworm might also be suffering from competition with European earthworms that reached the area with settlers as stowaways on plants.

“So it’s an incredibly interesting find and maybe it will allow us to say more about where and how it lives,” Johnson-Maynard said.

Three years of samples showed European earthworms live in far larger numbers in the prairie remnant, Sanchez-de Leon said. The largest numbers live in the farmland idled through long-term contracts under the federal Conservation Reserve Program.

Earthworms play important roles in soil health, transferring plant debris from the surface deeper in the soil and digging tunnels that allow air and water to penetrate.

Sanchez-de Leon said she plans to return to Smoot Hill this spring to search for the giant Palouse earthworm again. Johnson’s experience suggests they’re no easier to find the second time around.

“We went back a few years ago, about 15 of us from UI and WSU, and spent a rainy day looking in the exact same place but we didn’t find any,” he said.