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Livestock Grazing & Disease

Great Old Broads for Wilderness believes bighorn populations that are healthy, interconnected, and naturally expanding are a strong indicator of the overall health of public landscapes.

A Serious Species Decline

In the late 1800s, it is estimated there were 1.5 to 2 million bighorn sheep spread throughout the West.  They were the predominant ungulate in many mountain and canyon landscapes—more common than deer and elk. This iconic species was nearly extirpated by overgrazing, habitat fragmentation, unregulated hunting, and most importantly, disease carried by domestic sheep and goats that came with westward expansion.1

By the mid-1950s, only about 20,000 bighorns remained in the continental United States.

Very costly and sometimes dangerous translocations were successful in reestablishing herds in some historical home ranges, and conservation efforts increased the population of bighorns to approximately 70,000 by the year 2000. Since then, despite a variety of intensive conservation efforts, the overall population has stagnated or declined.  Many herds are less than 100 animals, isolated, and are at risk of developing problems related to lack of genetic diversity.

Although past efforts brought bighorns back from the brink of extinction, unlike other wild ungulates including deer and elk, bighorn populations have never significantly recovered.

In the West today, bighorns occupy less than 10% of their historic home range and number less than 5% of their estimated historic population.

The long-term sustainability of the species is uncertain, making them a sensitive species or Species of Conservation Concern (SCC) in many national forests where they occur.

The Threat of Domestic Sheep & Goats

The science is clear; respiratory disease from pathogens transmitted from domestic sheep has caused catastrophic all-age die offs and markedly reduced lamb recruitment (survival through first fall) in herds throughout the West. Reduced lamb recruitment can also occur in herds that have low grade infection, but do not suffer major die-offs. The negative effects of an infection can last for decades in a herd, resulting in chronic herd decline or stagnation.

Current scientific consensus is that the major threat to bighorn populations is a respiratory disease complex caused by a combination of pathogens carried by domestic sheep and goats.2 Amassed evidence points to Mycoplasma ovipneumoniae (M.ovi) as the primary cause of pneumonia outbreaks in bighorn sheep. DNA analysis of samples obtained from bighorns over the last 3 decades has clearly identified domestic sheep and goats as carriers, and the source of M.ovi infections in bighorns.3

Foray activity is a normal and expected behavior of bighorns. Young males and occasionally females leave their core herd in search of new grazing and breeding opportunities and then return to their herd. This behavior is essential for natural genetic diversity and connection between smaller herds in a metapopulation. Unfortunately, these walkabouts (often 5-20 miles) increase the opportunity for foraying bighorns to encounter domestic sheep grazing on public lands. Bighorns and domestic sheep are curious and attracted to each other. Close contact can result in the transmission of novel strains of M.ovi and other pathogens from domestic sheep to bighorns; bighorns can then spread the pathogens to other bighorns.

Separation of bighorns from domestic sheep is the cornerstone of science-based management efforts and the clear path forward for recovery of the species.3

Despite recognizing respiratory disease threats to bighorns, many state and federal agencies promote management alternatives that allow grazing domestic sheep on high-risk public land allotments near to or overlapping with known bighorn home ranges.

Agencies then rely on “best management practices” (BMPs) or adaptive management strategies for separation. These strategies may include hazing bighorns, using guard dogs, using additional herders and even euthanizing bighorns that come near or in contact with domestic sheep on public lands.

These BMPs come from the Western Association of Fish and Wildlife Agencies (WAFWA) guidelines and according to those guidelines, are “not proven and therefore should not be solely relied upon to achieve effective separation”.4

In addition, state agencies concerned about potential spillover disease events have adopted bighorn herd management plans that call for stable, rather than increasing, populations and distribution by increasing the number of hunting permits issued for specific herds.   These decisions are made in an effort to reduce the risk of contact between bighorns and domestic sheep and come at the cost of not having bighorn sheep expand into significant portions of suitable, historic habitat.5

There is no practical, effective vaccine or medical treatment available for domestic or wild sheep and there are none on the horizon. The only solution is to remove chronic carriers by capture and test and cull persistently infected individuals.6 This strategy is very expensive, often dangerous, and leaves healthy members of the herd at risk for another new exposure from domestic sheep.

Pro grazing advocates correctly note that many bighorn herds are infected with M.ovi and appear to be healthy.  They claim that bighorns and domestics have been on the landscape for decades and both are doing fine.  Just because a bighorn herd is already infected with M.ovi is no guarantee that they aren’t at risk of another exposure and possible disease event. “There are many strains of M.ovi carried by domestic sheep and goats and infection with one strain will not prevent future infection by another strain. Because of the potential for a significant die-off within an infected bighorn herd, spread of disease to other herds and long-lasting impacts on lamb recruitment, the consequences of transmission from domestic animals to bighorn sheep are severe.”7

In short, bighorns in wild landscapes need elbow room, free from domestic sheep to naturally expand their populations and thrive.

Our position

Broads encourages and supports agencies and conservation groups working together to develop and employ progressive standards that allow bighorn population recovery, enhancement, and interconnectivity on public landscapes including:

States, tribes, and federal agencies using best available science to recommend closing or vacating high-risk domestic sheep allotments. To identify areas where domestic and wild sheep have the greatest risk of contact, Broads encourages use of the Bighorn Sheep Risk of Contact modeling tool.8

Allotment retirement programs that take a market approach to help change grazing patterns, turn opponents into partners, and provide a solution to chronic conflicts between domestic sheep and bighorns on public lands. This approach can reduce litigation, and reshape grazing to be compatible and sustainable, and incent allotment retirement with fair market buy-outs.9

State and federal agencies prohibiting the use of domestic goats for noxious weed control in occupied bighorn habitats on public lands due to the risk of pathogen transmission from domestic goats to bighorns.10

Advising people to not use pack goats in bighorn habitat on public lands. Colorado Parks and Wildlife recommends that people “LEAVE YOUR PACK GOATS AT HOME.” Diseases can be transmitted even if animals appear healthy.11

Employing these strategies will help manage bighorn herds and wild landscapes in a manner that supports vigorous, sustainable bighorn populations— a worthy goal for all agencies and conservationists.

Broads in Action – Citizen Science

In 2017, Colorado Backcountry Hunters and Anglers (BHA) spearheaded a citizen-science effort to help state and federal agencies gather verifiable observations of the presence of bighorn sheep in and near active domestic sheep grazing allotments in the Weminuche Wilderness. In 2018 Great Old Broads for Wilderness joined forces with BHA, Rocky Mountain Bighorn Society, and Mountain Studies Institute to form the Colorado Bighorn Monitoring Program which is now active throughout all the San Juan Mountains in Southwest CO.  Broads have assisted with posting official signage about the citizen science effort at trailheads, held public information and volunteer training sessions and have actively participated in sightings of bighorns and domestic sheep in and near allotments in SW CO.

For more information and how you can join Broads in this citizen-science effort please visit:

Broads is encouraging local Broadbands in other western states to initiate similar citizen-science efforts.

Take Action:

Please take a moment to send an email to the following decision makers with the following bullet points in your own words:

  • Disease transmission from domestic sheep and goats to wild sheep is a significant risk factor for the conservation and restoration of wild sheep populations.
  • Effective separation of domestic sheep and goats from wild sheep is the only currently available management solution for preventing or minimizing disease transmission.
  • Current and proposed alternative management strategies (BMP-best management practices) may result in the continued loss of wild sheep from disease.
  • Bighorns in wild landscapes need elbow room, free from domestic sheep to naturally expand their populations and thrive.
  • Agencies need to work cooperatively to close domestic sheep allotments in occupied and historic bighorn habitats.

In Colorado:

Governor Polis

Colorado Department of Natural Resources, Dan Gibbs, Executive Director

Colorado Parks and Wildlife Director and Commission

BLM Colorado State Director, Doug Vilsack

Regional Forester of the USDA Forest Service Rocky Mountain Region, Frank Beum

Footnotes & Resources

  1. The Wildlife Society Fact Sheet, Impacts of Disease on Bighorn Sheep Management. 2014
  2. The Wildlife Society and American Association of Wildlife Veterinarians Joint Issue Statement, Domestic Sheep and Goats Disease Transmission Risk to Wild Sheep. 2015
  3. Kamath, P.L., Manlove, K., Cassirer, E.F. et al.Genetic structure of Mycoplasma ovipneumoniae informs pathogen spillover dynamics between domestic and wild Caprinae in the western United States. Sci Rep 9, 15318 (2019).
  4. Western Association of Fish and Wildlife Association (WAFWA) Recommendations for Domestic Sheep and Goat Management in Wild Sheep Habitat 2012
  5. CPW_BLM GFO Domestic Grazing Draft EIS Comments_Signed_081219 – TEM comments
  6. Garwood T, Lehman CP, Walsh DP, Cassirer EF, Besser TE, Jenks JA. Removal of chronic Mycoplasma ovipneumoniae carrier ewes eliminates pneumonia in a bighorn sheep population. Ecol Evol.2020;00:1–12.
  7. Besser Declaration, Case 2:20-cv-00440-RMP ECF No. 21 filed 02/26/21 PageID.1039
  8. USFS and BLM Bighorn Sheep Risk of Contact Tool
  9. Embattled Bighorns, National Wildlife Federation Magazine, June-July 2016
  10. Risk Analysis of Disease Transmission between Domestic Sheep and Goats and Rocky Mountain Bighorn Sheep 2017
  11. Colorado Parks and Wildlife recommendation on pack goats