USFWS EIS Addresses Plummeting Population Decline Of Hart Mountain Bighorn Sheep Due To High Cougar Predation, Poor Habitat

The U.S. Fish and Wildlife Service is announcing a Notice of Availability for the final Environmental Impact Statement to address a significant decline in the California bighorn sheep population on Hart Mountain National Antelope Refuge.

The Service is partnering with the Oregon Department of Fish and Wildlife to develop the bighorn sheep management plan for the refuge.

The bighorn sheep population on the refuge has declined by 67% in four years, dropping from 149 sheep in 2017 to 48 in 2020. This trend puts the population at severe risk of extirpation without management intervention. The population decline is a result of high cougar predation and declining habitat quality due to juniper encroachment and invasive plants. Of the 19 sheep radio-collared on the refuge in January 2019, 10 have died. Seven of those deaths are attributed to cougar predation.

The final management plan will include a combination of management strategies to reduce bighorn sheep predation mortality caused by cougars in the short-term while providing time to identify and correct habitat issues that may take decades to resolve. The Service will temporarily and strategically lethally remove cougars in bighorn sheep habitat to allow the herd size to recover to a sustainable level. Habitat management would focus on the herd range and address life history needs to expand and enhance habitat conditions.

“We’re extremely concerned about the steep decline in the population of bighorn sheep on the refuge,” said Robyn Thorson, Columbia-Pacific Northwest Regional Director for the Service. “The Service and ODFW are working together to develop this management plan that will enable us to avoid extirpation while implementing long-term solutions for habitat improvement. This plan will help us save this population of bighorn sheep.”

Bighorn sheep were extirpated from Oregon by the 1940s due to disease and unregulated hunting. The first successful reintroduction of this native species occurred at Hart Mountain in 1954, when 20 California bighorn sheep from British Columbia were successfully released. Hart Mountain’s population served as an important source population for bighorn sheep transplants to other parts of Oregon and surrounding states.

Bighorn sheep hunting on Hart Mountain has been suspended by ODFW due to the declining population. The Service, in coordination with the ODFW, would not restart any sheep hunting until their population reaches a sustainable level and predator control by the refuge is discontinued.

The final EIS and additional information on the refuge and the sheep population can be found here.

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