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Closing grazing allotments on Weminuche Landscape essential to promote viable populations of bighorns

This spring, the U.S. Forest Service will announce a long-awaited decision on the Weminuche Grazing Analysis Draft Environmental Impact Statement.

Columbine District Ranger Matt Janowiak’s decision, which is being reviewed at the regional and national levels, will have important ramifications locally and throughout the West for bighorn sheep populations and domestic sheep producers.

The core issue for bighorn management is whether the Forest Service will continue to allow domestic sheep grazing in historic bighorn habitat on the Weminuche Landscape.

Historically, bighorn sheep were once among the most abundant wild ungulates in the American West. Population estimates range from 1.5 to 2 million at the onset of the 19th century. Bighorn populations declined with westward expansion of human populations because of market hunting, introduction of domestic sheep and overgrazing of rangelands.

Aggressive restoration and protection efforts have allowed populations to grow in the West from an estimated 25,000 in 1955 to 70,000 now. Growth in population in Colorado reflects these efforts, increasing similarly from an estimated 2,000 in 1955 to 7,000 now. Yet in recent years, bighorn population growth has stagnated across the West despite continued restoration efforts.

Current scientific consensus is that bighorn populations fail to thrive in large measure because of recurrent herd-level respiratory disease outbreaks associated with exposure to domestic sheep. According to a joint issue statement of The Wildlife Society and the American Association of Wildlife Veterinarians released in March 2015, “... it is now apparent that disease transmission from domestic sheep to wild sheep is a significant risk factor for the conservation and restoration of wild sheep populations,” and “effective separation of domestic sheep from wild sheep is the only currently available management solution for preventing or minimizing disease transmission.”

The closure of domestic sheep grazing allotments has been used in other states as an effective management tool to protect and promote viable bighorn populations. In March 2016, the 9th U.S. Circuit Court of Appeals upheld a 2010 Payette National Forest decision to phase out active sheep grazing permits.

Weminuche bighorns are listed by the Forest Service as a sensitive species, meaning there is concern for their long-term viability. Locally, the Weminuche bighorn population numbers about 425 animals, which is about 73 percent of the San Juan National Forest’s estimated total population of just 585 animals.

The Weminuche population, comprised of herds in Game Management Unit S28, GMU S15 and GMU S16, is designated as a highly valued “Tier 1” population because it is believed to be one of only three herds statewide that have received little or no augmentation. That means these are true native bighorns, and as such, they represent an important historic gene pool for the San Juan Mountains and for the state.

The Vallecito herd (GMU S28), which summers nearest the current active grazing allotments, has struggled to maintain viability and currently numbers only about 60 members. This herd is most at risk for exposure to domestic sheep, and because it is interconnected with the GMU S15 and GMU S16 herds, a disease outbreak in the Vallecito herd could easily spread to the greater meta-population, resulting in the potential loss of all of the highly-valued bighorns on the Weminuche Landscape.

Management of Weminuche bighorns is the direct responsibility of Colorado Parks and Wildlife. The Forest Service is responsible for managing bighorn habitat and livestock grazing on the Weminuche Landscape. Grazing domestic sheep has been allowed for decades in the Weminuche despite growing controversy over its effects on bighorn populations. In the Weminuche Grazing Analysis (despite scientific consensus regarding the risk to bighorns), both agencies have recommended continued domestic sheep grazing on the landscape.

It appears both agencies have been unduly politically pressured by agriculture interests, as documented in a joint letter signed in 2014 by Bob Broscheid, director of CPW, and John Salazar of the Colorado Department of Agriculture, and in a memorandum of understanding signed by the agencies and the Colorado Woolgrowers Association in 2013. These documents, submitted in the analysis, disregard accepted science and instead effectively conclude “that closure of active sheep allotments will not be recommended based solely on the potential for interaction between domestic and bighorn sheep.”

The results of a decision to continue to allow domestic sheep grazing in historic bighorn habitat on the Weminuche Landscape are predictable and potentially catastrophic. It is normal, expected and locally documented that young bighorn rams and ewes wander many miles in search of new grazing or breeding opportunities. As such, there is no way to ensure that contact and disease transmission won’t occur on the Weminuche Landscape.

Contact between domestic sheep and bighorns eventually will happen – with consistently deadly results for the exposed bighorns. As noted in a Durango Herald article (Nov. 30, 2016), bighorns exposed to domestic sheep are killed by CPW staff in a desperate effort to prevent further disease spread. Exposed bighorns that manage to return to herds may spread diseases that cause acute all-age die-offs or negatively impact lamb survival for decades. The failure of CPW and the Forest Service to recommend closure of grazing allotments is biologically reckless.

Closing all domestic sheep grazing allotments on the Weminuche Landscape is the only way to effectively protect and promote truly viable local populations of Colorado’s magnificent state animal.

Dan Parkinson, DVM, is Southwest Regional director of Colorado Backcountry Hunters & Anglers. Reach him at docdanp@gmail.com.

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