All Terrain Thinking

A Compendium of things I think are Important

Generally Speaking, Think on this...

Giant Palouse Earthworm,

Search is on for worms' wiggle rooms Sandi Doughton

November 15, 2007

COLFAX, Wash. – When searching for one of North America's most elusive creatures, it helps to have state-of-the-art equipment, jokes Jodi Johnson-Maynard.

The University of Idaho soil scientist is walking up a gentle hill in southeast Washington, on a quest for the giant Palouse earthworm. In her hand is a tile spade, a narrow shovel that's about as high-tech as it gets in the worm-hunting business.

Click Image for Larger The large, white worm at the top is the giant Palouse earthworm, Driloleirus americanus. Below is the southern worm or Aporrectodea trapezoides, which is considered an introduced species

GIANT PALOUSE EARTHWORM Scientific name: Driloleirus americanus Length: 8 inches to 3 feet; average 12 to 13 inches Girth: About the size of a man's little finger Color: Whitish pink Habits: Is said to spit lily-scented mucus when startled; feeds on fungi and detritus Mating: Worms are hermaphroditic, with both male and female organs. Habitat: Palouse prairie of southeast Washington and west-central Idaho Myth: Some people think cutting an earthworm in half yields two live worms. In fact, you get one dead one.

“It's our basic tool,” Johnson-Maynard says, leaning on the spade like a walking stick. The long handle is great for chasing away rattlesnakes, she says, and the sharp edges slice through turf.

Unfortunately, they also make mincemeat of worms. Two years ago, a graduate student unearthed one of the rare wigglers on this same hill, but accidentally cut it in two.

“We need better methods to look for these worms,” Johnson-Maynard says.

That's especially true now that conservationists are seeking endangered-species protection for the pinkish-white worms, which may grow to 3 feet long and were once abundant in the deep soils of the Palouse. Only four sightings have been confirmed in the past 30 years, and experts had feared the species was extinct.

Last month, the U.S. Fish and Wildlife Service rejected a petition filed by the Palouse Prairie Foundation, Friends of the Clearwater and others, saying too little is known about the worm to declare it endangered. But the conservationists filed notice that they will sue to force the federal agency to reconsider and launch a major review of the species' status.

“It's an ethical decision,” said Steve Paulson, the Idaho environmentalist who is leading the push for protection. “I don't think we should be causing these creatures to go extinct.”

If the worm is listed, its remaining habitat must be protected.

Since no one is even sure what habitat the worm favors, there's clearly a need for more study – which means being able to find the creatures, Johnson-Maynard says. Her early November expedition is aimed at testing one alternative to the shovel: saturating the ground around a worm burrow with a diluted solution of hot mustard and vinegar.

“The hope is that it irritates the worms and drives them up to the surface,” she says, passing through thickets of chokecherry and wild rose that dot this 40-acre remnant of native grassland. The 3,000-foot hill, part of a Washington State University biological reserve, rises like an island in a sea of wheat fields.

Less than 1 percent of the wild Palouse prairie remains; biologists suspect the giant worms have likely fallen victim to habitat loss, churning plow blades and competition from the night crawlers and other nonnative species that now dominate the region.

Johnson-Maynard drops her pack, slips off her parka and begins to dig. She kneels by the hole and breaks apart clods with her hand, searching for tunnels left behind as earthworms cruise through the soil, eating fungi and leaf litter.

“Here's a burrow,” she says, pointing to a barely discernible track among the roots, pebbles and dirt. “It's pretty subtle, but when you look at soil a lot, these things just jump out at you.”

With $25,000 from the Idaho Fish and Game Department, Johnson-Maynard will try several worm-hunting tools in the coming months. Washington's Department of Fish and Wildlife also is interested in sponsoring worm studies, but hasn't put up any money yet.

“Finding earthworms is hard work,” Johnson-Maynard says, scanning the buff-colored landscape for a promising spot. Early road crews reported giant earthworm burrows extending up to 15 feet underground. While naturalists in the late-1800s said the worms favored prairie, at least one sighting in the 1980s was in forestland.

With so little information on the species' behavior and preferences, going out armed only with a shovel is like sticking a fork into a haystack and hoping to pull out a needle, she says.

Some commercial worm hunters report success with electroshocking: sinking metal rods into the ground, then using batteries to generate a weak current that sends the worms to the surface. Johnson-Maynard has recruited electrical engineers to help her rig a similar system.

She's also keen to try DNA testing on the mucus worms leave behind in burrows, to help identify areas frequented by giant Palouse earthworms. It may be possible to train dogs to sniff out the worms, because some reports claim they spit lily-scented mucus when disturbed. (The scientific name, Driloleirus americanus, means lily-smelling American worm.)

Johnson-Maynard is even open to the idea of “worm grunting”: rubbing a metal bar against wooden stakes in the ground to create vibrations that cause worms to flee their burrows.

“We really don't know what will work,” she says.

The autumn light is starting to dim, and she's on her fourth hole. She stabs at the ground and her shovel lays open a burrow that's bigger than the others – possible evidence a giant Palouse has passed this way.

“Let's try the mustard here,” she says.

Support scientist Karl Umiker takes over, widening and deepening the hole. He pulls out three plastic bottles filled with the clear solution and empties them into the trench. The soil is dry and hard, and the liquid seeps in slowly – not an auspicious sign.

In dry weather, worms tend to enter a type of hibernation deep underground.

Umiker pokes around in the muddy hole with his shovel, gently scooping out soil and searching for any hint of white. A light-colored grub generates a brief stab of excitement. Umiker teases a hibernating worm out of the soil, but it's a common variety.

Johnson-Maynard shrugs. It was a long shot, she says, gathering up her gear for the trek down the hill. She'll return later this fall, after the rains have started and the rare worms might be more active.

“I think they're out here,” she says. “It's just a matter of coming on the right day, at the right time and using the right sampling technique.”

More info on the worm

Prior | Tell us what you think | Next

Add to Your Social Bookmarks: Del.icio.us Digg Furl Reddit Simpy Spurl Y! MyWeb - StumbleUpon