Desert bighorn thrive atop precipitous cliffs

This healthy ewe was fitted with a radio-telemetry collar and ear tags for identification purposes (Photo courtesy of Colorado Division of Wildlife)



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This healthy ewe was fitted with a radio-telemetry collar and ear tags for identification purposes (Photo courtesy of Colorado Division of Wildlife)

QUICKREAD

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This is the 10th in a series of weekly columns about Colorado National Monument in honor of the park’s centennial anniversary on May 24.

The desert bighorn sheep is a relative newcomer to this rocky old neighborhood of deer, coyotes, ravens, rabbits, lions and lizards. Prior to 1979, bighorn hadn’t resided in Colorado National Monument for centuries. There were none to be seen here.

“Extirpate” is the word wildlife officials use to describe the bighorn’s shadowy history. It means “to remove completely.” The species probably lived here in ancient times, but then disappeared from the region for reasons unknown.

So wildlife officials agreed to bring them back, to reintroduce the species to a landscape believed to have been inhabited by its ancestors. Dozens of bighorns were transported in horse trailers from Arizona and Nevada to the monument’s westernmost canyons between 1979 and 1995.

Today, about 40 desert bighorn sheep make their home at the monument, according to the Colorado Division of Wildlife. The monument’s bighorn are part of the Black Ridge herd, a growing population (now estimated at 200 rams, ewes and lambs) that roams the high desert west to the Utah border.

Their very presence enriches the monument ecosystem. Bighorns rank high on the list of watchable wildlife, too. People love to glimpse Ovis canadensis nelsoni and Ovis canadensis mexicana, scientific names for the subspecies of desert bighorn transplants.

One of those people is Paul Creeden of Fruita. “Sheep are my favorite mammal, I’ll tell you that,” he says.

Creeden, a DOW district wildlife manager, has spent decades observing all sorts of mammals, most of them wild and eager to avoid human contact at all cost. On occasion, of course, Creeden has to step in anyway.

Recently, he was part of a team that dispatched a mountain lion that had been helping itself to a rancher’s livestock. A year or so ago, Creeden unintentionally made news by freeing a skunk whose head was stuck inside a peanut butter jar. These extreme examples illustrate what Creeden, recently named DOW Wildlife Officer of the Year, does for a living.

But it was grad school research 30 years ago that laid the foundation for his expertise in this species. Creeden’s 1981–83 research project, “The Ecology of Desert Bighorn Sheep in Colorado,” earned him a master’s degree at Colorado State University.

His findings documented how transplanted bighorn swiftly adapted to their new home in western Colorado. Some examples:

Population increased 18 percent (from 34 to 40 animals) during 1979–81.

Delayed seasons of reproduction activities occurred in early years but such delays had disappeared by 1983.

Ewes preferred ledges at the base of sheer canyon walls and above steep talus slopes for lambing activities — all sites that would allow them to escape from predators.

His data provided benchmarks for bighorn monitoring that continues to this day. That assignment belongs to Stephanie Duckett, a DOW terrestrial biologist in Grand Junction.

She and a small team, tracking the Black Ridge herd with the aid of radio-telemetry, discovered good news continues here. The desert bighorn is thriving at a time when its cousin, the Rocky Mountain bighorn that inhabits higher elevations east of here, suffers from lung disease and struggles to survive.

Here at the monument, bighorns enjoy protection that high precipitous cliffs provide from predators, such as the mountain lion. Their healthy diet depends on nutritious forbs and grasses that grow throughout the monument. Needless to add, they have shown no plans to leave the neighborhood.

Nobody knows exactly why, but ancient desert bighorn were here one day and gone the next.

Evidence of bighorns’ presence has been documented in the form of Native American petroglyphs, and in archaeological digs. Ancient artists carved bighorns on canyon walls across the region, though skeptics say rock art doesn’t prove anything. Disease may have wiped out the ancient population, which is something biologists keep in mind.

So far, Duckett reports, the Black Ridge herd has shown no evidence of pneumonia and is “very, very healthy.” Other promising signs that reintroduction succeeded: The ratio of lambs to ewes is high, as is the survival rate of lambs.

“This is indicative of a growing, healthy population,” she says.

The future of desert bighorns relies on experts like Duckett, but also the rest of us non-experts who get a thrill whenever we spot them. Here are a few tips:

Allow bighorns ample room to roam because getting too close stresses them.

Never feed bighorns or any wildlife because it habituates them to people.

Dogs create stress for bighorns, so keep dogs off all trails at the monument and maintain control of dogs on other public lands where bighorn are present.

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Eric Sandstrom teaches at Mesa State College and is a seasonal park ranger at Colorado National Monument.



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