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Desert bighorn population in good health

Herd population is increasing; CPW seeks input on management

Desert bighorns roam the cliffs and pastures of the lower Dolores River canyon downstream of McPhee Dam, and Colorado Parks and Wildlife is seeking public input on their management.

CPW has released a draft herd management plan for game units S-63 and S-64, which cover the middle and upper stretches of the lower canyon in Montezuma, Dolores, San Miguel and Montrose counties.

Public comment is sought through December and can be submitted via email to: Montrose Terrestrial Biologist Brad Banulis at: brad.banulis@state.co.us

Population in the Dolores River corridor has stayed steady at 175 animals from 2016 to 2018. A gradual increase occurred since 2003, when an estimated 100 bighorn were in the canyon.

From 1994 to 2001, the population had grown to 235. But in 2001 there was a sharp and undetermined decline in population. Since then, numbers have rebounded.

“The population is doing well,” said Brad Weinmeister, a terrestrial biologist for Colorado Parks and Wildlife in Durango. “We have been seeing healthy animals producing good lamb numbers.”

He said habitat is plentiful for the herd to expand, and that is the hope. No studies are planned, and none of the bighorn sheep has active radio collars at this time.

Although bighorn sheep are likely indigenous, they were not present in the past century in the Dolores Canyon. The current population was established in 1986 with the release of 25 bighorn from Arizona.

The Dolores River bighorn herd offers limited ram hunting. For 2019, five ram licenses were available, two in S-63 and three in S-64. CPW said it might allow ewes to be hunted as the population increases.

For guidance, CPW conducted a public survey involving 130 participants. The majority of respondents wanted to see an increase in the population and were satisfied with the current ram hunting opportunity, according to the draft management plan.

“Based on available habitat and current health of the herd, the population has the potential to increase,” according to the draft plan.

CPW staff recommends a target population of between 175 and 275 desert bighorn in the Dolores River Corridor.

Desert bighorn attract trophy hunters seeking rams with larger curled horns. The plan recommends a running average horn length between 28 inches and 33 inches of harvested rams over a three-year period.

The plan explains that hunting restrictions allow rams to grow larger horns and increased ram licenses would reduce average horn length and trophy quality. Desert bighorn sheep licenses are highly sought and are offered to Colorado residents only under a draw system. Hunting success is usually 100%. A bighorn ram tag is the second hardest to draw, behind drawing a moose tag.

The Dolores Canyon desert bighorn population is relatively disease free, according to the study, but transmission of domestic sheep diseases remains a threat. Domestic grazing on public land in the Dolores Canyon has not occurred in many years, minimizing the risk.

Almost the entire occupied bighorn habitat is on Bureau of Land Management land, but some landowners in the area have sheep or goats that could interact with bighorn.

Domestic sheep carry diseases that don’t effect them, Weinmeister said, but if bighorn get infected with the domestic diseases, it can cause a die-off and suppress their numbers for some time.

In 2013, a collared ewe from the desert bighorn from unit S-63 was observed mingling with two domestic goats along Colorado Highway 90 that had escaped pens. The collared ewe was euthanized on March 21, 2013, after at least five days of mingling with the goats.

In addition to desert bighorn populations in Utah, the Dolores herd is near to Colorado desert bighorn populations – the Uncompahgre (S-62) herd to the east and the Black Ridge herd (S-56) to the north. Interaction between the herds have not been documented. However, canyon and rock rim corridors connect all the herds, albeit across unsuitable habitat. The Uncompahgre and Black Ridge herds have known disease issues.

CPW currently does not want to promote the possible connection of the relatively disease-free Dolores herd to the nearby herds. The report also notes that domestic sheep graze west of Gateway, within 5 miles of the Utah line.

The closest population of desert bighorn sheep to the Dolores River herd occurs in Utah along the Colorado and Green River near Moab. A bighorn from the Upper Dolores reportedly wandered downstream to Moab and mixed with a herd in Canyonlands National Park. By way of the Dolores River to the Colorado River, the distance is over 70 miles.

Recreation impacts

Increased recreational use along the Dolores River is a concern for CPW.

“The bighorn sheep range is experiencing an ever-increasing number of hikers, dogs, rock climbers, horseback riders, OHVs, mountain bikers and rafters on the Dolores River,” the plan states. “There is continued pressure to develop areas for recreation opportunity, and recreation is known to displace desert bighorn sheep.”

The draft plan recommended that disturbance from recreation activities should be considered, especially during critical times such as spring lambing and drought.

To protect desert bighorn from recreationists during a period of lambing and nursing, the BLM has implemented a road closure at the Pyramid and Joe Davis Hill from Feb. 1 to June 30 each year. However, the report says the road gate at the closure point often is left open or is illegally opened, and people continue to use the road. Compliance with the closure has improved in recent years.

Ewes are habitual about where they lamb, then all the ewes, lambs and yearlings come together to graze in areas where there is a good escape route into the cliffs.

“We’ve seen up to 60 bighorn in one nursery group,” Weinmeister said.

Within the canyon, bighorn are regularly seen from the river to the top of the rim.

Regular sightings occur along Colorado Highway 141 south of Slickrock, in Summit Canyon, Bishop Canyon, McIntyre Canyon, Grassy Hills, Bull Canyon, Gypsum Ridge, Spring Canyon, Coyote Wash and LaSal Creek. Concentration areas are at Joe Davis Hill and within 3 miles up and down river of Coyote Wash on the Dolores River as well as from LaSal Creek confluence to Bedrock.