Conservation Today

Desperately Seeking… Giant Earthworm That Smells of Lilies

"You then have a giant earthworm.  A giant earthworm that needs human help."

[Originally published on www.conservationtoday.org, 17 July 2009]

Rare species are exciting, and large rare species are especially exciting. From mythical creatures such as the Loch Ness Monster, to mysterious realities like the giant squid.  To the bones of long dead prehistoric megafauna, and the heavy hulks of the mountain gorillas.  Large and spectacular creatures deliver the ‘wow factor’ to the human imagination and seize our attention.

Now take that wow factor, and the humble earthworm.

You then have a giant earthworm.

A giant earthworm that needs human help.

The giant Palouse earthworm has only been seen four times since its discovery in 1894. In June 2009 several conservation groups banded together for a second time to petition the US Fish and Wildlife Service to protect the animal.  For the worm’s habitat is under threat from both human activity and invasive earthworm species. 

The Palouse earthworm has a whitish colour and can reach sizes of up to three feet long.  Particularly unusually, it is said to emit a smell of lilies when disturbed- hence the name, Driloleirus americanus, which means ‘lily-like worm’. Though not the largest earthworm in the world- that title belongs to the three metre Giant Gippsland worm of Australia- it is still one of the biggest species of earthworms, and it has an endearing quirk of spitting lily-smelling fluid at predators.

The few sightings of the earthworm have been in areas of the Palouse prairie region of eastern Washington and northern Idaho. It was first described by Frank Smith in an 1897 article in The American Naturalist, and apparently was a common sight of the times. Yet since then documented findings of these worms have only occurred in 1978, 1988, 1990 and 2005. For the worm is confoundingly elusive, and specific surveys for the worm have rarely found it.  2002 survey of 46 sites in the Palouse region did not find a single Palouse earthworm.  Meanwhile, other sightings have occurred during surveys for other purposes.  The most recent 2005 sighting was when a PhD student scraped up two pieces of six-inch Palouse earthworm during a soil survey.

Along with occasional groups of schoolchildren who go out on field trips to search for the worm, Professor Jodi Johnson-Maynard and her team from the University of Idaho are also on a mission to find living examples. In summer, the worm can burrow down to a depth of 5m to escape the drought. The techniques that are employed to find it range from basic methods of sifting through deep soil samples for worms hidden amongst the soil, to methods of forcing the worm to come to the surface- pouring an irritant solution of mustard and vinegar into the ground, or using probes to deliver electric shocks deep into the soil. So far, no Palouse worm has been produced, but the search goes on

Like the local farmers of the prairie, the worm prefers moist and fertile soil.  Steve Paulson, representative of the conservation group Friends of the Clearwater, said that urban sprawl and agriculture had claimed much of the worm’s natural habitat. He pointed out that the Palouse Prairie is considered one of the most endangered ecosystems in the U.S., with less than two percent remaining in a native state.

Whether its scarcity is a sign of population decline or its mastery of hiding itself, the rareness of the worm is even proving a barrier to its protection. The 2006 conservation petition to put the worm on the Endangered Species Act, constructed by the groups Friends of the Clearwater, Center for Biological Diversity, Palouse Prairie Foundation, Palouse Audubon and Palouse Group of Sierra Club was rejected by the U.S. Fish and Wildlife Service on the grounds that there was not enough information about the species. Critics say this is typical of the Bush administration, pointing out that 522 species were added to the Endangered Species Act during the Clinton regime, while only 62 have made the list so far in the Bush years.  It is hoped that a second petition with additional information will see the species safely protected, on paper.

Protecting the worm will have consequences for local farmers and make their livelihoods harder.  Yet earthworms are Nature’s natural soil tillers, keeping soils mixed and aerated.  Charles Darwin liked worms and investigated their behaviour with the help of his children. Perhaps one more species on the planet will be stopped from heading, unstudied and uncared for, into extinction. Perhaps these efforts will bring attention to the biodiversity of native earthworms and the value of their natural behavior to maintaining the quality of soil. Perhaps it will draw attention to the endangered prairie habitat and the other hidden organisms in its ecosystem. Either way, with groups joining ranks to conserve the Palouse earthworm, this looks to be one unusual species of worm which will not slip away unnoticed.

A profile of the Palouse worm - http://www.palouseprairie.org/invertebrates/palouseworm.html

Assistant Professor Jodi Johnson-Maynard discusses the Palouse worm - http://idahopublictv.org/outdoors/shows/palouseparadise/johnson-maynard.cfm