Wildlife officials in South Dakota are scrambling to assess and contain a dangerous outbreak of pneumonia in the state’s iconic Hell Canyon bighorn sheep herd. The respiratory disease, which can be fatal in up to 80% of cases, is a major threat to bighorn populations across the West.

“We’re extremely concerned,” said Tom Kirschenmann, wildlife division director with South Dakota Game, Fish, and Parks (SDGFP). “Pneumonia can devastate a herd, and we’re seeing telltale signs like coughing and lethargy.”

The outbreak was discovered by SDGFP biologists during a recent collaring project in Hell Canyon, a rugged and remote area known for its bighorn population. While the exact source of the outbreak is unknown, the leading theory is that the wild sheep may have come into contact with domestic sheep, which are known carriers of the pathogens responsible for pneumonia

Bighorn sheep are highly susceptible to these pathogens, and once infected, they can pass the disease to their young. This leads to low lamb survival rates and long-term population declines. 

The Hell Canyon outbreak is particularly concerning because the SDGFP was considering increasing the number of hunting tags for bighorn sheep in the area. These plans are now likely on hold.

No Cure, Only Prevention

Unfortunately, there is no cure for pneumonia in bighorn sheep. The main management strategy is to prevent contact between wild and domestic sheep – a challenging task.

“It only takes one interaction to put an entire herd at risk,” says Kirschenmann. “We work closely with ranchers and land managers to try and minimize contact, but it’s an ongoing battle.”

The situation in South Dakota underscores the fragility of bighorn sheep populations. Once common throughout the West, bighorns were nearly wiped out in the early 20th century due to overhunting and disease. Conservation efforts have helped restore populations in some areas, but pneumonia remains a major hurdle.

As for the future of the Hell Canyon herd, wildlife officials are hopeful they can minimize the damage. However, it’s clear that pneumonia outbreaks will continue to be a challenge for bighorn sheep conservation across the West.

©️ Rocky Mountain Dispatch 2024