Victory! Court Rules Grazing Decision Poses Unacceptable Threat to Bighorn Sheep in Colorado
9th of May 2025
The Tenth Circuit Court of Appeals handed down a major conservation victory for bighorn sheep conservation on the Rio Grande National Forest. The Court ruled the U.S. Forest Service unlawfully disregarded scientific findings and arbitrarily altered the findings of its disease “Risk of Contact” modeling when it approved domestic sheep grazing on the Rio Grande National Forest near Creede, Colorado in 2018.
The agency approved the creation of the Wishbone domestic sheep allotment in close proximity to bighorn sheep core habitats despite concluding in 2013 and 2015 that contact with domestic sheep posed a high level of disease risk to the area’s bighorn sheep populations. Advocates for the West represented Western Watersheds Project and WildEarth Guardians in a 2019 lawsuit challenging the decision to graze domestic sheep within the habitat range of bighorn herds.
“The Forest Service previously decided to vacate adjacent and overlapping domestic sheep grazing allotments because of the high risk they posed to bighorn sheep,” said Laurie Rule, Senior Attorney at Advocates for the West, who represented conservation organizations in the lawsuit. “But the agency then ignored the same threat in approving the new allotment. The Tenth Circuit recognized that decision was unreasonable and not supported by the science and data in the record.”
“Bighorn sheep on public land should be protected by the Forest Service, but in this case the agencies violated the public trust—and federal law—to facilitate commercial sheep use near critical bighorn sheep habitats,” said Delaney Rudy, Colorado Director for the Western Watershed Project. “We are relieved by the Court’s assertion that the Forest Service can’t choose to turn a blind eye to the acute threat that domestic sheep grazing poses to wild bighorns.”
“This is an important victory for bighorn sheep and for the requirement that agencies ground their decisions on facts,” said Chris Krupp of WildEarth Guardians. “Here, the Forest Service knew that bighorns would likely come into contact with domestic sheep, but it put its finger on the scale to reach the conclusion it wanted. That’s always unacceptable, but especially so here when the consequences to Colorado’s state animal are so deadly.”
Background
Contact between domestic sheep and bighorns is dangerous because of two deadly pathogens, Mannheimia haemolycta and Mycoplasma ovipneumoniae, that domestic sheep carry and transmit to bighorn sheep. Once a wild sheep is infected through contact with a domestic sheep, they carry that pathogen back to their herd and even to other herds, which can lead to catastrophic, all-age die-offs. There are currently at least seven herds in Colorado that are experiencing population collapse due to illnesses from domestic sheep.
Four bighorn herds inhabit national forest lands near the newly-invented Wishbone Allotment: the San Luis Peak, Bellows Creek, Bristol Head and Rock Creek herds. Three other bighorn populations live within easy traveling distance for a bighorn ram: the Weminuche population to the south, the Natural Arch/Carnero population to the east, and the San Juan West population to the west. Overall, approximately 1,100 bighorn sheep are at risk from domestic sheep grazing on the Wishbone Allotment.
At Issue
The Forest Service itself has recognized disease as “the greatest concern for bighorn sheep population persistence (in) the Rio Grande National Forest.” Bighorn sheep on the Rio Grande National Forest are designated as a species of conservation concern, a designation that requires all agency actions to be analyzed for their potential impact to bighorn sheep and maintain bighorn sheep population viability.
The Tenth Circuit held that the agency’s explanation for approving the Wishbone Allotment relied “on no science or data, and in fact contradicts the data in the record about bighorn sheep movement and permittees’ compliance with project design features.”
