CPW staff goes to great lengths to monitor Colorado’s bighorn sheep

CPW wildlife biologist Lance Carpenter sits on a ledge in Waterton Canyon watching a bighorn ram on Friday, Nov. 30. Photo courtesy Colorado Parks and Wildlife / Jason Clay.
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Jason Clay

DENVER – When it comes to conservation of Colorado’s majestic and agile Rocky Mountain bighorn sheep, Colorado Parks and Wildlife staff battles jagged walls, steep cliffs and the weather, both good and bad, across the state to fulfill their mission.

Such was the case Wednesday along I-70 where the winds were whipping and temperatures in the 20s. CPW staff conducted a survey of the Georgetown bighorn sheep herd, spreading teams out across eight different locations looking for rams, ewes and lambs from Golden to the Continental Divide.

CPW monitors the state’s bighorn twice annually, once in the summer and once in the winter to gauge how many lambs survive their first six months as well as to calculate the ram to ewe ratios. The winter is the preferred survey time because the rams, ewes and lambs all congregate together in lower elevations during this breeding season, referred to as the rut.

“Bighorn herds are surveyed to monitor productivity, general abundance trends, distribution and disease,” Wildlife Biologist Ben Kraft said. “This allows CPW to manage towards the herd’s objectives, which are set by the public. The surveys that are conducted in Georgetown today, have been occurring since 1948.”

So you see, this is a longstanding practice of the state’s biologists monitoring its wildlife and thus, a lot has been learned through these efforts to help conserve the animal that disease and unregulated hunting almost wiped out in the early 1900s.

Disease can take a toll on Colorado’s bighorns. One historical example of drastic disease impact took place in the Kenosha and Tarryall Mountains. Historical literature states these mountains had the largest sheep herd in all of North America – reportedly in the 2,000-3,000 range. Today, both the Kenosha and Tarryall herds range in size from 40-60, so disease can cause an all-age die-off.

“Disease is a major concern because it may lead to respiratory illness throughout a herd,” Kraft added. “This can result in a large proportion of the herd dying and the absence of lambing for a very long time. In a worst case scenario, entire herds have been lost because of disease. Researchers are still trying to understand which ‘bugs’ and environmental conditions lead to all-age die-offs, but the mechanism of disease introduction into bighorn herds is co-mingling with domestic sheep and goats.”

A known remedy to help combat disease epidemics is to keep herd sizes from getting overpopulated and to keep domestic and wild sheep separated.

“When bighorn herds increase beyond the carrying capacity of their habitat, herd productivity decreases while disease increases,” Kraft said.

That is just some of what has been learned through these surveys over the years, which take place in a variety of ways. However, many of Colorado’s bighorn sheep populations live in remote, rugged areas with limited human access, making this information expensive and time consuming to collect.

A lot of miles – many of them of the steep variety – are hiked by CPW staff, but the use of aerial drones, fixed-wing aircraft and helicopters help from above on many surveys. Whether surveys are conducted in the air or on the ground depends on funding and environmental conditions.

The Northeast Region team of CPW biologists has plans for six bighorn surveys this winter. The Southeast has 11 on its docket and the Southwest has eight. All are aimed to take a look at what is an estimated statewide bighorn population of 7,000 animals.

The current affairs among Colorado’s bighorn sheep is that the state’s herds are healthy and in good numbers. That is thanks to the efforts of many constituents dedicated to conservation of the state’s wildlife.

“The persistence of bighorn herds is a community effort by landowners, local and federal land managers and CPW,” Kraft said. “When I see the robustness of bighorn in Colorado, I know that a significant amount of forethought and effort has gone into managing Colorado’s habitat and appreciate the natural landscapes that Colorado has to offer.”

Location of bighorn surveys in the Northeast region of Colorado:
Poudre Canyon
Big Thompson Canyon
St. Vrain
Waterton Canyon

Other well known bighorn herd locations across Colorado:
Tarryall and Kenosha Mountain herds
Mount Evans/Grant herds

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1 Comment

  1. In August and October of 2018 two articles were published in High Country News on CPW management of bighorn sheep in Colorado. These articles detailed how domestic sheep authorized by the BLM and Forest Service to graze in bighorn sheep habitat on public lands in Colorado contribute to the repeated die-offs and prolonged population suppression that has hamstrung bighorn sheep recovery. The article above was written by CPW in an attempt to counteract that exposure.
    CPW here states that: “The current affairs among Colorado’s bighorn sheep is that the state’s herds are healthy and in good numbers.” This couldn’t be further from the truth. Many of Colorado’s bighorn sheep populations have experienced a die-off caused by pneumonia in the last few decades, and most of those populations remain suppressed years after the initial die-off occurred. Lambs born to bighorns that survive a disease event aren’t immune to the pathogens still carried by their mothers, and will often die shortly after weaning. It can be twenty years or more years before a herd decimated by pneumonia begins to grow again. Some herds never recover, and dwindle to extinction.
    Why, then, do the Forest Service and BLM continue to authorize domestic sheep grazing in bighorn sheep habitat? And why has CPW signed an MOU with the state’s domestic sheep producers agreeing not to advocate for bighorn sheep on public lands where domestic sheep are putting herds at risk?
    Bighorn sheep were noted during the time of the Lewis and Clark Expedition as one of the most abundant game animals in the West. They now number 7000 in Colorado. Colorado has more than 250,000 elk. The status of bighorn sheep reflects neither “robustness” nor “a significant amount of forethought” in management.
    Coloradans, please research the factors impacting bighorn sheep. Review the documents obtained through CORA by High Country News, and ask Colorado Parks and Wildlife why they are planning to renew an MOU that imperils iconic native wildlife.

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