Disease, big cat threaten bighorn herd in Crystal Valley
December 11, 2008
CARBONDALE ” A respiratory disease is killing bighorn sheep in the Crystal Valley and threatening the viability of the Avalanche Creek sheep herd, according to the Colorado Division of Wildlife.
And a hungry mountain lion isn’t helping.
The herd’s biggest problem is a highly contagious disease called pasturella, said John Groves, a wildlife manager for the Carbondale district who has been studying the herd in recent years. Pasturella tends to kill lambs within six to eight weeks of their of their early June birth dates. Research indicates that 90 to 95 percent of the lambs born annually have died off in the last two years, Groves said.
That high mortality rate has taken a toll on the herd’s standing. Data indicates the Avalanche Creek herd’s population hovered around 250 in the late 1980s and early 1990s. Now it is estimated at around 70. The wildlife division feels it must intervene.
“This year we’re going to start inoculating,” Groves said.
The adults will be inoculated so that they don’t pass pasturella to the lambs. As much of the herd as possible will be baited later this winter, then trapped with a net. Wildlife officers and qualified volunteers will administrator the shots.
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A bighorn sheep herd in the Fryingpan Valley has been inoculated at times in recent years for lung worm, but the Avalanche Creek herd hasn’t been previously treated.
This will be an experimental program the wildlife division is trying because of the widespread threat of pasturella.
“We’re seeing a lot of this through all herds in the state,” Groves said.
Parts of the Crystal Valley, south of Carbondale, provide prime habitat for the bighorns. The Filoha Nature Preserve established by the Pitkin County Trails and Open Space is an important winter range for a large share of the herd. The 190-acre property is closed from Sept. 30 through June 30 and restricted the rest of the year.
The pasture, river and natural salt and mineral licks lure the animals off the nearby cliffs and serve as “a kind of bighorn spa,” said John Armstrong, a ranger with the Pitkin County Trails and Open Space program. The bighorns are a common site at Filoha Meadows throughout the winter months.
“It’s very, very common and almost predictable” to see them, Armstrong said.
And that’s something the bighorns’ predators have learned. A commuter driving by on Highway 133 last week saw a mountain lion in the process of capturing and killing a bighorn. Armstrong said when he heard about the sighting, his first thought was, “Cool ” Mother Nature at work.” But after conferring with Groves he learned it wasn’t so cool, at least not in this case, because of the toll from pasturella.
“You hate to lose any sheep that are survivors,” Armstrong said.
Groves said one mountain lion appears to be prowling the Avalanche Creek and Filoha area and feasting on the bighorn herd. He found three or four carcasses from lion kills last winter. They typically stick close to steep cliffs where the excellent climbers can make quick escapes, but sometimes they get caught in more open terrain. Normally he wouldn’t be concerned about a few lion kills, but he is “when I have a herd that’s teetering already.”
There are no plans to trap and kill the lion, but Groves wouldn’t be sad to see the big cat become a target itself during a hunting season.
Meanwhile, the wildlife division is assessing whether to issue any hunting tags for the Avalanche Creek bighorn herd during the recovery effort. When the population was at its peak, the agency issued 12 tags for the limited hunting season for bighorns. In recent years, that has been reduced to just two tags. No bighorns have been harvested there for the last couple of years, Groves said. Hunting is tough because the elusive animals live in such steep and inaccessible terrain. No decisions has been made on issuing tags in the next few years.
The wildlife officer said the public can assist with the recovery effort by obeying closures and restrictions on public lands in the Crystal Valley. In addition to the closure at Filoha Nature Preserve, dogs are banned during winters in Avalanche Creek. Cross-country skiers are restricted to the road.
“These closures are there for a reason,” Groves said.