Escalante Canyon – The small cave along the Gunnison River stinks to high heaven and is dotted with piles of the fish- bone-flecked scat of river otters. John DePue is arm-waving overjoyed as he hops from a raft and lands amid the mess.
“Oh, yeah! Oh, man! Look at this!” he says. “This is a gold mine!”
DePue has good reason to be excited when he comes across such a fine otter latrine. He has logged more than 2,000 miles over the past four years floating eight rivers in the state to hunt down signs of one of the state’s most elusive critters for the Colorado Division of Wildlife.
The otter is so slippery that DePue has seen only two in the wild in all that time. That’s OK. He’s zeroing in on what they leave behind in order to determine how many there are in the state.
DePue’s study involves kneeling in mud to tweeze otter hairs from a wire device and scooping up poop and an odoriferous jelly substance.
But it represents a state-of- the-art step forward in tracking a species that was wiped out in Colorado by fur trappers in the early 1900s and reintroduced between 1979 and 1991. DePue’s innovative use of collecting data with low-tech items such as wire and paper clips combined with high-tech DNA analysis is expected to change the way otter surveying is done across the country. It also may result in otters being removed from the threatened-species list in Colorado.
“It should be more accurate than anything that’s been done before,” said Pam Schnurr, DOW wildlife conservation biologist. “We’re making otter history.”
Schnurr hired DePue, a University of Wyoming graduate student doing his master’s thesis on otters, to try to determine how Colorado’s reintroduced population is faring.
Efforts to count otters in other states through surveying, sightings, conventional trapping and capturing have been stymied by these wily members of the weasel family.
Otters hunker down in riverside dens, mainly coming out at night. When they do, a single otter can track up more than 5 kilometers of riverbank. So they can’t be counted like bighorns or bear.
Capturing otters doesn’t work well because once trapped, otters rarely fall for the same trick again, and recapturing animals is an important step in estimating population numbers.
Otters can’t be collared or tagged. Their torpedo-shaped bodies and minuscule ears don’t accommodate such things. Surgically implanting tracking devices isn’t a preferred method.
DePue, 30, grew up canoeing the rivers and lakes of northern Wisconsin and Minnesota and has trapped fox in the Channel Islands, wildcats in South America and bear in Idaho. After two years of doing the typical surveying of otter tracks and scat in Colorado, he set out to find a new way to trap scientifically sound evidence of individual otters without actually capturing the animals.
Practicing on otters at a wild-animal rehabilitation center near Telluride, he devised a wire snare that does just that.
DePue positions the snare in otter latrine areas or on riverbanks where the otters’ distinctive tracks – distinguished by horizontal ridges between the toes – show they have clambered ashore. When an otter is guided through the wire by a barrier of sticks that DePue erects, the wire tightens around the animal’s body enough so that a few hairs are tugged out by jagged snips DePue has made in strands of the wire.
DePue also uses a standard leg trap with a hair-collecting wire brush in the opening that is large enough for the animal to exit without harm.
The follicles in the hairs that DePue collects and catalogs will be checked for genotype once DePue is back in the university lab this fall.
So will the scat and the DNA- rich anal jelly, which is a substance otters secrete to help pass scat filled with the spiky bones of the crawfish, frogs and fish they consume.
DePue’s river travels have already yielded visible evidence of about 120 reintroduced otters.
“From what I’ve seen, they are faring pretty well,” DePue said. “They are reproducing.”
Staff writer Nancy Lofholm can be reached at 970-256-1957 or nlofholm@denverpost.com.
