Keeping track of Glacier Park's bighorn sheep

Posted on 10 March 2016

By DAVE REESE


From his office in Bozeman, Kim Keating is keeping his finger on the pulse of Glacier National Park's bighorn sheep.

Keating, a research biologist with the U.S. Geological Survey, is in the middle of a groundbreaking six-year study of the park's Rocky Mountain bighorn sheep. His study will give park officials better information on how to manage the park's bighorn sheep population.

"It's designed to give the park a firmer idea of where they have sheep, what are the movement corridors and how things like fire suppression might affect sheep habitat," Keating said.

Such an in-depth study has never been done in Glacier and Keating says his work will give park managers long-term scientific data, not just postulations. Keating says there's been a longstanding gap in the amount of knowledge of the park's 400 to 600 bighorn sheep.

"Sheep, as a management issue in the park, come and go," Keating said. "Every few years, sheep become an issue because of something that comes up, whether it's a die-off, impact from a hotel reconstruction or highway work."

Just as biologist Doug Chadwick did in the 1980s with the park's mountain goats, Keating's study will help guide management of bighorn sheep.

Although he did research on sheep more than 20 years ago, Keating's knowledge base was outdated and limited and unable to meet today's management needs, he said.

"People were still calling me up and asking me, 'What can you tell me about these sheep?' Recalling information from the 1980s was a not a good way to manage them," he said. "We needed a firmer foundation than that. I told the park, 'If you want information about sheep, it's time to do it right.' Glacier is not Yellowstone; they don't have 100 years of really solid data that they can refer back to when these issues come up and they have to make decisions."

The study began in 2002 and will run through 2007. In the last three years Keating and his team have radio-collared 86 sheep; they have recovered 46 of the collars, which download to a computer the exact movements of the sheep over the previous year.

With the knowledge they glean from the recovered radio collars, Keating's team is learning much about the travel and habitat of the park's bighorn sheep. For instance, fire suppression in Glacier Park could have a major impact on sheep because of the continual encroachment of coniferous trees on the sheep's grassland habitat.

While Keating's study is not meant to yield population estimates, he does have an idea of the park's sheep population trends.

The park's sheep underwent two years of "absolutely phenomenal" reproduction and survival in 2003 and 2004, with lamb-to-ewe ratios of 80:100. "I've never seen that before, it was incredible," Keating said. "It was the sheep population's own baby boom."

Now things have returned to normal, and the population is seeing lamb/ewe ratios of about 35 lambs per 100 ewes.

What was interesting about the sheep baby boom in 2003-04 is that it followed a severe spring of 2002, when late-season snowstorms wiped out the lamb crop and took its toll on the older rams in the herds.

"They're amazing animals with their ability to recover and bounce back," Keating said.

Sheep may be able to rebound from the damage that severe weather causes, but Keating wonders about a more long-term danger: more trees. An expanding forest of conifers like Douglas fir and subalpine fir can take its toll on sheep habitat, he said. Sheep inhabit rocky outcrops and open grassland to feed upon, and "when you get a lot of trees encroaching it really degrades the habitat for them," Keating said.

There are two distinct subpopulations of sheep in Glacier Park - one in the north and one in the south - with St. Mary Lake being the general dividing line. Evidence from DNA collected from female sheep droppings shows that there is little interchange between the two subpopulations.

KEATING AND HIS biologists have placed 20 to 30 radio collars on sheep each year. The animals

are tranquilized, fitted with a collar, then released.

Once a sheep is fitted with a radio collar, it gathers the sheep's location every five hours by using GPS technology. A mechanism in the collar is programmed to release the collar after one year. Each collar will collect between 1,400 and 1,600 locations per sheep each year, and over the years Keating has pinpointed roughly 55,000 unique locations gathered from the collars.

That's a big difference from having to use older, analog radio collars that might have collected only 50 locations a year, Keating said. "Technology is a wonderful thing if you use it right. We put the collar out and let it do its thing."

Recovering the collars can be a challenging part of the biologists' job. Sheep inhabit some of the most rugged, remote portions of Glacier, and where the collar drops is where biologists have to find it.

"I've found myself crawling down ice-covered ledges or hiking into some pretty remote areas with no trails," Keating said.

The signal that the released collar emits is similar to that of an avalanche transceiver. The transmitting signal from the collar is prone to bouncing off the steep rock walls in Glacier, and Keating said he's had to spend two to three days "chasing in the wrong direction" to find a collar.

By tracking sheep throughout the year, Keating has discovered some astounding feats that the animals have performed.

One sheep traveled from the south end of Glacier near Marias Pass north to Curly Bear Mountain, a distance of roughly 21 air miles. The distance on the ground was much greater. (Curly Bear Mountain is the northernmost peak along the ridge that separates the Red Eagle and Divide Creek drainages.)

One radio-collared ewe apparently swam across St. Mary Lake from Dead Horse Point over to Red Eagle Mountain - twice. "That's a pretty remarkable movement, if it's true," Keating said.

Most of the travel of the sheep subpopulations is between their seasonal ranges. One heavily used winter area is near Mount Altyn in Many Glacier. "Sheep have been using that for thousands of years," Keating said.

Sheep seem to venture rarely outside their traditional seasonal ranges. "Unless there happens to be a traditional travel corridor, it's pretty unlikely they're going to go exploring," Keating said.

Bighorn sheep don't occupy nearly as large an area as they did historically and they have been susceptible to disease from domestic sheep, mainly on the east side of the park, according to Keating.

"Parts of their native range just got wiped out," he said. Sheep have evolved to be able to handle subzero temperatures and rugged terrain, but they can't outrun disease or a hunter's bullet. The sheep, Keating said, seem to know where the park boundary line is on the east side of the park where they might be more susceptible to hunting. They rarely venture outside the park and are not prone to crossing highways.

Inside the park, the sheep have a world to themselves, and it's Keating's job for the next two years to study that world. The information from his study will help park managers for years to come, he hopes.

But the best part of his job is not monitoring the sheep from his office in Bozeman - it's being in Glacier. "One of the perks of work like this," he said, "is getting to be in some absolutely gorgeous areas."


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