SEVERANCE, Colo. — Since he was a boy in western Colorado, John Bartmann seemed destined to become a sheep man. He raised lambs with the local 4-H club and sheared them for elderly German farmers. His office is lined with paintings of sheep and a plaque honoring him for “promoting culinary excellence” in lambs.

But over the last few years, skyrocketing costs, a brutal drought and plunging lamb prices have battered Mr. Bartmann and the 80,000 ranchers across the country who raise sheep — from a few to several thousand. It is the latest threat to shadow a Western way of life that still relies on the whims of summer rains, lonely immigrant sheep herders and old grazing trails into the mountains.

“For the sheep industry, it’s the perfect storm,” Mr. Bartmann said, glancing out his office window here at a bleating sea of wool. “The money is just not there.”