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ND Mixing of Subspecies
A bit of interesting reading regarding the mixing of Rocky Mountain and California Bighorns. This is now the second time this has been done - Wyoming did it first with a relocation of California Bighorns from Oregon in December of 2004.


Posted on Sat, Mar. 04, 2006

NORTH DAKOTA OUTDOORS: Bighorn sheep entice N.D. puzzle

Species stirs considerable interest, despite small population

By Doug Leier

North Dakota doesn't have many bighorn sheep, but vast appreciation and genuine curiosity from hunters and nonhunters alike more than compensate for the lack of population.

While this could be said for many North Dakota fish and wildlife inhabitants, the bighorn sheep fills a niche as the only kind of wild sheep in the state.

As with any subject matter, knowledge creates a greater appreciation.

For years, scientists debated the basic classification of North America's bighorn sheep. North Dakota had a native bighorn that was called the Audubon. This animal became extinct in the early 1900s.

North Dakota did not have any wild sheep from that time until the mid-1950s, when bighorns from British Columbia were transplanted here. Sheep from that area were considered a subspecies called California bighorns, while sheep from much of the West were called Rocky Mountain bighorns.

North Dakota remained home to California bighorns until recently, when scientific genetic investigations determined that California, Rocky Mountain and Audubon sheep were, in fact, all the same species.

Major impact

On the surface, this may not seem like an earth-shattering discovery, but it likely will make a significant difference in North Dakota.

From 1956 on, North Dakota focused its sheep management on California bighorns. Transplants had to come from areas where the California subspecies lived, such as British Columbia, Idaho and Oregon, all of which are long distances away and contain habitat that is not all that similar to North Dakota's Badlands.

Because Rocky Mountain bighorns were considered a different subspecies, they couldn't be brought into North Dakota, even though they lived a lot closer, because they would mix with the California sheep.

The logical train of thought was that introducing the same strain of sheep would make for better odds of long-term success.

The recent re-examination of bighorn sheep changed that philosophy and herein lies the result. This past January, 19 bighorn sheep were transplanted to North Dakota from Charles M. Russell National Wildlife Refuge, which encompasses both sides of the Fort Peck Reservoir on the Missouri River in eastern Montana. The sheep that live in the Missouri Breaks on the western end of Russell are considered as Rocky Mountain bighorns and previously were not an option for transplanting, though they live only a couple hundred miles from North Dakota.

Now that the former California bighorns also are considered as Rocky Mountain sheep, a new era of bighorn management is under way.

When opportunities for getting new sheep are available, as they were this year, the closer proximity means less travel stress for the animals, so it makes sense that transplanting sheep from Montana would have the potential to yield better short- and long-term results than moving animals from Oregon or Idaho.

Habitat benefit

Beyond location, habitat similarity is another benefit. The Missouri River Breaks has similar grass, soil, elevation and other crucial elements to a successful transplant. In this best-case scenario, as the sheep are released, biologists hope after a few moments in the North Dakota Badlands, the new inhabitants will think, "This is just like home."

The most recent transplant pushed the state's bighorn population to 250. With a future goal of carrying 300 bighorn sheep, more work remains.

Safe lambing grounds are a key factor. Bighorn sheep need considerable acres of rough terrain and limited disturbance where ewes can easily watch out for danger.

While visibility and terrain are more features of geography, disturbance is a human factor.

Deep in the heart of the Badlands, the possibility of human disturbance would seem limited. But any amount of disturbance to lambing sheep will result in abandonment, no matter how clear the sight path or steep and rugged the terrain.

Disease issues also weigh heavy on bighorn sheep populations. Less than a decade ago, North Dakota sheep experienced a massive die-off south of Interstate 94. Dozens of sheep deaths were linked to a bacteria called Pasteurella haemolytica a strain that kills bighorns and is carried in domestic sheep and goats.

Even if sheep survive exposure to the disease, research has shown residual effects can result in lamb mortality from pneumonia for up to five years. This domino affect of disease, mortality and low reproductive success is an equation that can take decades to overcome.

Current policy with the U.S. Forest Service limits domestic sheep and goats from grazing on Forest Service land within 10 miles of known bighorn sheep habitat. This buffer zone minimizes interaction, but there is nothing keeping this from happening on private land within bighorn country.

Current Game and Fish Department policy calls for immediate dispatching of any bighorn interacting with domestic sheep. The historical die-off and documented potential to wipe out entire herds is too great of a threat.

While the bighorn sheep population likely will never rival that of other states, these animals are an invaluable piece of the beautiful puzzle that is North Dakota.

Leier is a biologist for the Game and Fish Department. Reach him by e-mail at
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