Big Horn Sheep

A bighorn sheep nibbles on a branch along the Yellowstone River near Gardiner on Jan. 7, 2010.

When biologists began a transplant project in the Madison Range last winter, they didn’t know it would turn into part of a comprehensive study that could help preserve wild sheep throughout the West.

Next winter, four Montana State University researchers and dozens of Montana Fish, Wildlife & Parks biologists and volunteers will begin a six-year study of bighorn sheep in an effort to determine why some herds grow and remain healthy while others fail to thrive.

FWP has awarded the study with $1.2 million, much of which came from the Wild Sheep Foundation. For the past few years, the foundation has held hunting-license auctions, which have brought in as much as $480,000 for one license.

Montana’s 2010 wild-sheep management plan sets a goal of establishing five new populations by 2020. But so far, no transplants have occurred, partly because of disease worries.

That’s what stopped a transplant operation last winter in the Madison Range, said MSU ecologist Bob Garrott.

Garrott has been conducting a five-year study of wild sheep and mountain goats in the greater Yellowstone area, so he helped out when biologists trapped and attached radio collars to wild sheep in the Tayler-Hilgard area in December.

The sheep were to be transplanted to the northern Madison Range, but biologists noticed a few animals were coughing, a sign of pneumonia.

Two months later, when they returned to check the collars, they found three dead sheep, so they cancelled the operation.

Bighorn sheep herds in several Western states have suffered large die-offs due to pneumonia. In 2010, 20 percent of Montana’s sheep died from pneumonia.

Fortunately, in the Madison Range, none of the other 200 or so sheep got sick, causing Garrott to suspect that the herd has the right combination of factors to keep it healthy.

“The sheep had all the pathogens that are associated with pneumonia,” Garrott said. “Based upon the presence of pathogens and everything in the literature, we expected a pretty serious event, and it never happened. That just illustrates why we’re doing this study.”

Almost three-quarters of Montana’s herds have less than 100 animals, limited by any combination of disease, predation or starvation. Garrott wants to know what makes the healthy herds hum.

With the Madison herd already tested and collared, Garrott and his crew now have the money to use the same techniques on six other herds this winter, from Kalispell to the Missouri Breaks to the Stillwater River basin.

Out of almost 50 herds in Montana, the seven herds in the study were chosen because they represent a wide variety of situations with different environments, histories and perhaps genetics.

While the Madison and Missouri Breaks herds are healthy, herds in the Anaconda and Butte Highlands areas are barely hanging on.

With so many variables, Garrott will depend on MSU ecologist Jay Rotella to run the statistical analysis to find out which variables might make the difference.

If it comes down to the genetics of either the animals or the bacteria – maybe one herd has a mutation that improves its immunity – then College of Agriculture geneticist Jennifer Thomson may find the key. But her part of the study isn’t covered by the grant money.

“We’re already collecting the samples, which is the most expensive part. So that should help her find the funding to run the genetic tests,” Garrott said.

People have often assumed that wild sheep die because they’ve come into contact with domestic sheep, which can carry bacteria believed to kill wild sheep.

“Everyone blames domestic sheep every time we have a die-off, but it’s not clear that’s always the case,” Garrott said.

That’s excited some people who want to transplant wild sheep into the Bridger Range, which has some small domestic sheep operations nearby.

Garrott cautioned against moving forward with a transplant like that yet.

“It costs a lot of money to do it, and it doesn’t help to create another unhealthy herd,” Garrott said. “We’re hoping this five or six years of study will show what things go together that allow herds to be successful in spite of the pathogens.”