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Researchers track bighorn sheep in Yellowstone

Radio collars track sheep, mountain goats

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A Rocky Mountain bighorn ram grazes along the road in the Lamar Valley on the northern edge of Yellowstone National Park. (Michael Gallacher, The Missoulian)

YELLOWSTONE NATIONAL PARK — A handful of bighorn sheep in and around Yellowstone National Park are wearing radio collars.

The bighorn sheep and another small population of collared mountain goats are providing data on how — and even if — the two species, which evolved together, interact. That will allow public lands officials to make informed decisions on management of the two species, said Bob Garrott, a Montana State University professor and researcher with the school's ecology department.

The study is in its fifth year, Garrott said, and he expects the work may go on for several more years.

Mountain goats — the white, longhaired, photogenic animals often seen in imagery relating to Glacier National Park — are not native to the Yellowstone area, Garrott said. The goats were introduced by Montana wildlife officials back in the 1940s and 1950s, Garrott said, from native populations located in western Montana. The goats were introduced into several areas west of Yellowstone, including in the Madison Range.

"The convention of the time was to get animals on the landscape even though they were not native," Garrott said. "People enjoy seeing them, and hunters enjoy pursuing them."

Mountain goats are not often visible from Yellowstone's roadsides, but may be seen at higher elevations on popular backcountry trails.

There are 300 to 500 of each species in the Yellowstone area, Garrott said.

He said his research team collared 16 bighorn sheep and 14 mountain goats on Yellowstone's Northern Range. Data already gathered by the GPS component of the electronics in the collar have already revealed some migratory patterns of the sheep.

Garrott had suspected that sheep that summer on Mount Washburn winter on Mount Everts, near Mammoth Hot Springs. The data from the radio collars confirm that, he said. The sheep migrate to lower elevations between Mammoth Hot Springs, and along the Yellowstone River outside of Gardiner.

Garrott said some of the objectives of the study are to determine if there is competition between the sheep and goats. The two species frequent similar habitats and eat similar forage, Garrott said. So far, they don't seem to interact much, he said.

The study also seeks to learn if climate change is affecting bighorn sheep. For example, with snow at higher elevations melting sooner, this can change the timing of when forage is available. These changes, along with the gradual increase over the years of the mountain goats, could impact the population size of the bighorn sheep, according to a study overview on Garrott's MSU website.

Bighorn sheep are susceptible to a disease called lamb pneumonia, which can be fatal to bighorn lambs at around 2 to 3 months of age. The disease was introduced into the wild population by domestic sheep, similar to how brucellosis, which came initially from domestic cattle, is now seen in bison, Garrott said.

Researchers suspect — but don't know for sure — that mountain goats can also be a vector for pneumonia, of which there may be several strains, just like in humans, Garrott said.

The study will also provide basic ecological research on the two species: what they eat, where they eat, population density and other information.

The purpose of the research is to provide information so public lands managers can make informed decisions about managing the non-native mountain goats. The managers might decide to leave the mountain goats alone, try to decrease their numbers, or even eliminate the non-native species altogether, Garrott said.

The information gathered aids in the understanding of other species, Garrott said.

"Everything we do applies to lots of other critters as well," he said.

In addition to Garrott and other MSU researchers, collaborating agencies on the study include the National Park Service, Wyoming Fish and Game, Montana Fish, Wildlife and Parks, Idaho Fish and Game and the U.S. Forest Service. Funding comes from state and federal agencies and non-governmental agencies like the Wild Sheep Foundation. Canon, the camera company, provides significant funding.


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