Detection dogs tracking scent of elusive vole
Woollett, with Working Dogs for Conservation, holds a vial with scat from a white-footed vole, which was used to train the detection dog.
PATRICK’S POINT STATE PARK, Humboldt County — Wicket, a black Labrador mix, zigzagged through a hillside of ferns, nose to ground, and abruptly sat down near a tangled thicket, a clear signal that she had found something important.
Could it be, at long last, the lair of the mysterious white-footed vole, the near mythical rodent of the redwood forests rumored for more than a century to be all but extinct?
The group of researchers following Wicket investigated, but alas it was nothing but the smelly black calling of a bear. Bear poop, it turns out, is one of the 22 scents besides vole scat that Wicket has been trained to track.
Fact is, nobody knows what connection, if any, white-footed voles might have to bears, other wildlife or, really, the very redwood forests that scientists believe is their primary habitat in Northern California. That’s because environmental scientists know next to nothing about the elusive species.
“It’s so weird that there is a species in the United States that we know nothing about,” said Tim Bean, an assistant professor of environmental
science at Humboldt State University and one of the lead researchers in a new project to locate and categorize the furry mahogany brown creature with characteristic white feet.
“The one thing we know is that they like red alder trees” near water in old growth redwood forests, said Scott Osborn, a senior environmental scientist for the California Department of Fish & Wildlife.
Mystery mammal
The species, which, based on the few specimens that scientists have studied, are genetically distinct from other voles. It is the only documented North American mammal that researchers have never studied and know so little about.
This is why a 10-yearold female dog with a small jingling bell hanging from its harness was leading a team of vole researchers along a forested creek bed this past week into a patch of alder trees. The detection dog, trained by the group Working Dogs for Conservation, is part of a study funded largely by San Francisco’s Save the Redwoods League to determine the vole’s habitat, range, population and characteristics.
The team of researchers is trying out several different detection methods, including pitfall traps and 40 trail cameras, none of which have yet worked very well, according to Bean. The detection dogs, which can actually distinguish white-footed vole scat from that of seven other vole species known to inhabit the region, may be the most promising method, he said.
“This way, over here, good girl,” said handler Debbie Woollett, directing Wicket to a spot near an alder tree. Woollett was watching the dog closely for subtle behavioral changes or agitation, which sometimes occur when she detects something but can’t locate it.
Wicket’s challenge
Wicket, one of eight dogs trained for conservation purposes, has tracked invasive snails in Hawaii, elephants in Africa, grizzly and black bears in Canada, a rare Moon Bear in China and was even able to find invasive Chinese Bush Clover in Iowa for an eradication campaign.
But the white-footed vole, known scientifically as Arborimus albipes, may have been Wicket’s most difficult job. The soft, furry creature is, as far as researchers know, only found in Northern California and Oregon. It looks like a mouse, but has a stouter body and slightly rounder head. It is about 2- to 3-inches long and is believed to spend part of its life in trees and the other part in burrows in the ground. The closest known species are red tree voles and Sonoma tree voles, both of which are arboreal.
“The ones we caught disappeared right into the ground,” Osborn said. “One was released in a tree and climbed way out on a branch then went back to the ground.”
Judging by the 155 other known vole species, white-footed voles probably eat seeds, roots, berries, plants and insects and have life spans of six to 12 months. They are undoubtedly prey to many species, including spotted owls.
A catch-22
The bashful beings are listed by the state and federal governments as a species of concern, but that is mainly because nobody knows how many of them there are or even where they live. Specimens have been found over the past century in only eight locations in coastal Oregon, the Oregon cascades and in the redwood forests of Northern California. The southernmost location was Arcata, where specimens were collected in 1899, Bean said. The last time anybody looked before now was in 2004, when state trappers did not find a single vole.
Finding voles this summer became a bit of a catch-22. The only way the dogs could search for them was to first have samples of vole scat so they could be trained. The researchers consequently put out 320 traps and spent 2,560 nights monitoring the contraptions. The best kind of trap, they found, was to connect two coffee cans with the tops cut off and bury them, placing a thin covering of leaves over the opening so that the voles would fall in. Using this method they caught three voles, two just north of Patrick’s Point and the third at Jedediah Smith Redwoods State Park.
The voles, named Marco, Sophia and Osborn by giddy scientists, provided Wicket and another tracking dog named Lily, with the scent they needed to begin their search. The dogs have alternated searching at Jedediah, Patrick’s Point and other locations for 16 days, but have yet to detect the reticent rodents.
“People thought they were very rare, but it may just be that they are hard to catch,” Bean said. “The problem is, we just don’t know.”
Ecosystem puzzle
The researchers hope to eventually find out what role the vole plays in the redwood ecosystem, in the food chain and in a slowly changing habitat.
“Saving the redwoods means a lot more than saving redwood trees. There is the story of the redwoods and this is a piece of it we just don’t know,” Bean said. “This is the northern range of the coast redwood, but the southern range of the white-footed vole, so there is also a climate change aspect to this. Is it temperature and precipitation that keeps the vole here? Will they disappear if that changes in the future? Understanding that question about what is keeping the whitefooted vole here is understanding the redwoods themselves.”
Wicket was tired and appeared to be discouraged by the futile search, so Woollett decided to give her an incentive. One of the researchers held her while Woollett surreptitiously hid a vial of vole scat under leaves at the base of a nearby tree. It took Wicket less than a minute to locate the vial, sitting down happily and looking expectantly at her trainer.
“Good girl,” Woollett said, handing the ecstatic canine her favorite red ball.
“She needed a motivational sample,” Woollett said, as Wicket scampered off to blissfully chew and toss around the slobbery ball.
The search for the white-footed vole would have to continue another day.