Bighorn sheep update: some herds show recovery while others remain at historic lows; agency continues testing and targeted removals
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Summary
Biologist Chad Lehman told the commission that statewide bighorn sheep counts improved from a low in 2025 but several herds remain affected by Mycoplasma ovipneumoniae; Badlands herd is near historic lows with 28 animals remaining and ongoing carrier removals, while other herds show good lamb-to-ewe ratios and lower MOB prevalence.
Senior wildlife biologist Chad Lehman summarized the department’s recent bighorn sheep surveys and ongoing disease-response work.
Lehman reported survey results from six primary herds (Badlands, Deadwood, Rapid City, Custer State Park, Hell Canyon, Elk Mountain). He explained Mycoplasma ovipneumoniae (MOB) transmission risks from domestic sheep and goats and how yearling rams can contact those reservoir animals and then spread infection to wild herds. "It can either be nose to nose contact, or it can be aerosol droplets," he said, and stressed that wild bighorn sheep suffer high mortality rates when exposed.
Some herds are showing encouraging signs: capture and testing in one herd returned a 16% MOB prevalence among 51 animals sampled and adult ewe/rams survival rates were high with lamb:ewe recruitment good, prompting continued test-and-remove efforts. By contrast, Lehman said the Badlands herd has fallen from almost 300 animals historically to 28 today, with a 21% carrier prevalence; Badlands National Park has removed 19 carriers so far and continues removal to try to restore herd health.
Lehman urged continued testing, selective removal of carriers, and close collaboration with federal and neighboring state wildlife managers on shared herds. John Canton, terrestrial section chief, said the commission will consider adding one additional license in Hell Canyon at the April meeting after reviewing this year’s data. Lehman and staff said more monitoring and capture work are planned and that testing will guide targeted management moves.
