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Any Wolverine? It's still mystery

Data inconclusive as state considers reintroduction

Gary Gerhardt, Rocky Mountain News

Published November 6, 2004 at midnight

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Of the few people who have seen a wolverine in Colorado, Ed Prenzlow is among them.



Prenzlow, a biologist who worked for the Colorado Division of Wildlife for 24 years, was making an elk count on the Flat Tops Wilderness Area south of Trapper's Lake in the late 1960s with Jack Grieb, then chief of research and later director of the division, and Cliff Coghill, a wildlife technician.

"We were riding horseback and came across a calf hiding along the path," Prenzlow said. "We dismounted and were checking the calf when something caught our eyes about 75 yards across a ravine on a ridge.

"It was dark brown and loping along right out in the open. We watched it for 5 or 10 seconds.

"We all said, 'What the heck was that?' and after ruling out a bear, a fisher or a coon, it had to have been a wolverine."

It's been said seeing one is something one never forgets, because no other animal spells wilderness like wolverine.

They are nasty tempered, cantankerous, foul smelling, unable-to-get-along-with-their-kind-except-during-mating, carrion-eating carnivores that only can survive if they have plenty of space and undisturbed denning areas.

Wolverine are the largest member of the mustelid, or weasel, family, which includes badgers, river and sea otters, pine martens, fishers, minks, black-footed ferrets and possibly skunks. For certain, while all carnivores have scent glands, this group's are super-sized.

It is said "pound-for-pound, the wolverine is the toughest critter on earth." That might be more impressive if the critter weighed more than 50 to 70 pounds.

I have read they are capable of backing a grizzly bear off the carcass of an elk and chasing off a wolf pack from its kill. It's possible their insatiable appetite is because of a scarcity of food.

While they are tough, and in some circumstances it might be true larger animals back away, tough is as tough does. Chief reasons for their mortality are trapping, predators and starvation.

The New York-based Wildlife Conservation Society reported in 2002 it was tracking a radio-collared wolverine in the Yellowstone area when it received a mortality signal - the animal hadn't moved in several hours. They found it and saw the wolverine had been killed when it tried to drag an elk carcass away from a bear.

Naturalist R.D. Lawrence wrote: "If the wolverine has an enemy, it is hunger. Nature, realizing she had created too perfect a fighting machine, turned the wolverine's stomach into a weakness.

"Despite his cunning, his enormous strength, his courage in battle and his endurance against cold and fatigue, hunger kills the wolverine by depleting his energy and making him vulnerable to attacks from other predators and to the many parasites and microbes the beast harbors in his body."

To satisfy this great hunger, the wolverine's main diet includes rabbits, mice, gophers, birds, rats, eggs and carrion.

Still unanswered, though, is the question of questions: Are there wolverines in Colorado? That has nagged biologists for almost 30 years, and they are no closer to answering it now than they were then.

In the past 25 years, the division has had 38 sightings rated as "B" - pretty darn credible, said Lyn Stevens, a state wildlife biologists.

"All the reports rated 'A' were escapees from zoos," she said.

Statewide, there were 17 sightings in Eagle, Garfield, Grand, Jackson, Moffat, Pitkin and Rio Blanco counties; 13 in Gunnison, Hinsdale, La Plata, Mineral, Ouray and San Juan counties; and eight from Chaffee, Conejos, Larimer, Park, and Pueblo counties.

A "verified" sighting requires a photo of the animal, a photo of a track or a dead animal.

Before the state started reintroducing lynx in 1999, researchers spent 20 years conducting investigations in Colorado to document the presence of lynx or wolverine.

Intensive efforts using snow tracking (5,8331/2 miles), hair snags (62 locations), remote cameras (110 locations) and snares (686 trap nights) yielded only 11 sets of tracks with a high probability of being lynx.

But in March, the Wyoming Game and Fish Department reported Kemmerer wildlife biologist Ron Lockwood was called out to remove a dead wolverine from U.S. 30 near the Fossil Butte National Monument.

That's plenty close to Colorado for an animal capable of traveling several hundred miles in a jaunt.

Lynx program started

The idea for reintroducing lynx and wolverine that finally resulted in the lynx program started in 1996 on what a group of division biologists and their new director, John Mumma, now refer to as the "infamous" Dolores River raft trip.

Along with Mumma were Rick Kahn, Tom Beck, Jeff Madison, Jim Hicks, Dave Kenvin and Gene Byrne.

As Byrne remembers, it was during that three-day trip the topic was discussed and Mumma was very supportive of the idea.

After the trip, Mumma went about setting up a working group with federal officials, and it was decided because of a lack of personnel and money, they should limit it to the lynx in the beginning.

"Also, I remember there was some talk with Canada about trapping wolverine, and we were told lynx were on a high population cycle and it would be far easier and less expensive to trap them," Byrne said.

Mumma said the staff recommended the lynx, although the wildlife commission gave permission at the time for both animals.

Byrne said during the late 1990s, Kenvin looked at all the large habitat blocks in the state and evaluated them using a geographic information system database and computer analysis.

"We looked at forested habitats with large blocks of high elevation habitats; prey base - deer, elk, small game; wilderness areas; road and human densities, and so forth," Byrne said.

"In the end, the southwest corner of the state - essentially the Rio Grande and San Juan national forests - had the best habitat," he said.

"And members of the working group felt the likelihood of a successful reintroduction of wolverine would be very favorable, probably even better than lynx."

Rick Kahn, state wildlife division big game supervisor and lynx recovery coordinator, said, "We had Jeff Copeland, who worked on lynx in Idaho come down in 1998 and look at Colorado habitat.

"It was merely a flyover and brief assessment, but Jeff thought Colorado had a good amount of denning habitat and obviously, our deer and elk populations provide a significant winter food source from carrion."

But researchers feel a concern regarding the reintroduction is obtaining enough animals of the right gender and age and having the money and manpower to complete the project.

"They are a lot harder to capture than lynx," Byrne said.

The researchers say the pluses to a reintroduction would be:

• It would be proactive in recovering a species that drastically has declined and is of special concern in most of its historic range.

• Could help prevent a future federal listing.

• Restore a scavenger and predator to Colorado's wildlife legacy and natural ecosystems.

• Wolverine pose low risks to humans or domestic livestock.

• Wolverine are of little threat to living big game species.

However, the drawbacks are:

• Wolverine could cause property damage by preying on small domestic animals and raiding cabins.

• Many people dislike the idea of reintroducing any predator.

• Being able to capture enough wolverine would be difficult.

• The evidence is not good that wolverine ever existed in the state in sustainable numbers.

• Wolverine reintroduction probably would be costlier than lynx and might need a private donor with deep pockets to achieve.

• The political climate was more favorable for a lynx reintroduction that it was for wolverine.

• Wolverine are reclusive wilderness species and their habitat would need protecting with large expanses kept undeveloped. That would mean controls over public lands, especially livestock grazing, mineral development, motorized recreation, timber harvest and watersheds.

Gulo gulo

• Scientific name: Gulo gulo, meaning "glutton."

• Description: 30-70 pounds, height 13-17 inches; long, dense fur, dark brown to black with creamy-white stripe running from shoulders along flanks to base of tail; thick body, short legs, short ears, broad flat head. Its non-retractile claws are long, curved and made for digging through snow for animals below.

• Life span: Up to 17 years.

• Terrain: Boreal forests and tundra, preferring marshy areas such as lowland spruce forests; remote areas; solitary throughout most of the year.

• Food: Carrion, especially elk and deer, rabbits, gophers, chipmunks, ground squirrels, mice, beaver, birds, eggs and berries. Primarily a scavenger.

• Birthing: Litters of as many as four are born between January and April, often in snow caves consisting of two tunnels as long as 60 yards long. Kits weigh less than a pound and are blind at birth. They wean at 8 weeks age and leave their mothers at 5-6 months.

Sources: Alaska Game And Fish Department, The Big Zoo.Com; Mammals Of Colorado By James Fitzgerald, Carron Meaney And David Armstrong; Wild Animals of North Americaby National Geographic Society.



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Comments

  • September 1, 2008

    11:41 a.m.

    Suggest removal

    budmayer writes:

    I have a picture of a wolverine that I took on last Friday. I was driving up the Old Fall River Road in RMNP. Just above timberline I noticed this unusual animal sitting on a large rock. I took several pictures of it. It was very large, brownish-black. It stayed frozen for all the time that I was watching it and taking pictures. But it did move its head. I would be glad to send one of the pictures to someone interested in reintroducing the wolverine to Colorado.