Most Montana Bighorn Herds at Risk

Restoring wild sheep requires risk management, partnerships

USGS_ovis_canadensis_GNP_bighorn_rams_0Credit: U.S. Geological Survey. Photo By: Kim Keating
The National Wildlife Federation and partnering wildlife groups say the future of bighorn restoration depends on reducing the risk of disease by reaching agreements with sheep ranchers. With 39 of 46 Montana bighorn sheep herds at risk of disease passed from domestic sheep, this problem is the main obstacle to future restoration.

Contact between domestic and bighorn sheep exposes wild sheep to bacteria carried by outwardly healthy domestic sheep; these bacteria cause pneumonia, typically lethal to bighorn sheep.

While several factors influence bighorn sheep restoration, pneumonia is widely considered the most important limiting factor. Pneumonia outbreaks have the potential to cause 30-90% mortality of a bighorn population. Additional outbreaks continue to occur within a herd several years after the initial outbreak, affecting lamb survival. Once a herd is exposed to pneumonia, it is often continually affected, making it extremely difficult for the population to recover, much less thrive.

“We need to do more to protect bighorn herds from respiratory disease because population recovery is so much harder after a pneumonia outbreak,” said Tom France, Regional Executive Director for the National Wildlife Federation in Missoula.

The solution highlighted in the report is for hunters and other wildlife conservationists to work collaboratively with domestic sheep producers to reduce risk of contact. The report “Challenges and Opportunities for Bighorn Sheep Conservation in Montana” takes the first step toward doing that by identifying domestic sheep flocks within 20 miles of established bighorn sheep herds in the Big Sky State.

The risks are real. Last year, pneumonia outbreaks caused significant die-offs among bighorns near Paradise and Gardiner. Twenty-six bighorn herds in Montana experienced large die-offs between 1984 and 2015, with more than half of these die-offs occurring in the past decade.

“During winter 2009-2010 pneumonia outbreaks in the West, Montana bighorns took the biggest hit of any western state or province, losing an estimated 20% of our statewide total,” said Brian Solan of Helena, president of the Montana Wild Sheep Foundation. “In addition, many of those herds have not rebounded from that disease event and have continued to struggle with lamb recruitment almost seven years later.”

The worst-case scenario is playing out in the Tendoy Mountains of southwestern Montana, where a once-thriving bighorn herd has never recovered from a pneumonia outbreak in the 1990s. Via hunter harvest, followed by agency removal, Montana Fish, Wildlife, and Parks (FWP) managers are currently eliminating Tendoy bighorn sheep which still carry the disease, inhibiting population recovery. Once infected bighorns have been completely removed from the Tendoy Mountains, FWP’s goal is to start a new herd by introducing disease-free bighorns.

“Our mission is to put and keep sheep on the mountain, which means raising and spending millions of dollars of private money to translocate sheep, and trying to keep them healthy following release,” said Kevin Hurley, conservation director of the Bozeman-based Wild Sheep Foundation Conservation. “In putting and keeping sheep on the mountain, the Wild Sheep Foundation works closely with wildlife managers, domestic sheep producers, and sportsmen stakeholders.”

While there is no simple solution suitable to all situations, the wildlife groups urge increased awareness of the risk to bighorns, increased collaboration with producers and a multi-faceted effort to keep bighorns and domestic sheep separated in time and space.

“The good news is that win-win solutions exist that will make bighorns more secure; separation is the key,” France says. “We need to work together to keep wild and domestic sheep separated, or we risk one bighorn die-off after another.”

“Bighorn sheep are a symbol of Montana’s wild heritage, treasured by hunters and all Montanans,” said Kathy Hadley, president of the Montana Wildlife Federation. “This report lays out some of the key issues surrounding bighorn sheep restoration around the Treasure State. Tt also shows the importance of finding ways to work together with landowners who have domestic sheep if we’re going to restore bighorns into their historic ranges, grow their numbers and ultimately build more hunting opportunity for this incredible species.”

You can read the full report via National Wildlife Federation’s website Bighorns Big Risks