Mountain goats spotted in Grand Teton National Park during an aerial flight last month have renewed worries that the nonnative species could compete with the park’s vulnerable bighorn sheep herd.

National Park Service and Wyoming Game and Fish Department biologists said four mountain goats were spotted in Cascade Canyon during a count of the Teton Range Bighorn Sheep Herd in March. Biologists say the sheep herd, which numbers roughly 100 animals, is vulnerable because it is isolated from other sheep and because it subsists on marginal, high elevation terrain.

Grand Teton National Park senior wildlife biologist Steve Cain said wildlife managers are monitoring the goats for now but could take more aggressive management action – including removal – if there’s evidence the goat population in the park begins to increase.

“Certainly, we view the goats as exotic species and would not like to see them become established in the park,” he said.

Idaho Fish and Game transplanted mountain goats to the Snake River Range in 1969, and the species moved into Grand Teton by 1977, Cain said. Since then, the park wildlife managers have received 74 reports of mountain goats in the Teton Range; 38 of those reports were in the park.

“The important piece of this is that, over the years, these observations have been small numbers of individuals,” said Cain. “We’ve never had strong concern that there was a population being established in the Tetons.”

“That changed last year,” Cain continued. “We observed nannies with kids.”

In 2009, the park received seven reports of goats in the Tetons, one report on national forest land and six in Grand Teton. The largest number of any of those observations was three adult goats and one kid.

“If this nanny was in the park and then had an offspring, it could be the first red flag signaling perhaps some animals that are going to stay and reproduce here,” Cain said.

A goat also was seen and photographed on the shoulder of Fremont Peak in the Wind River Range southeast of Jackson last summer. The range, much of it national forest wilderness, also is a haven for bighorn sheep.

Wyoming Game and Fish has only two hunt areas for goats, one in the Snake River Range and one in the Beartooth region east of Yellowstone.

Other national parks have experienced problems with mountain goats. In Olympic National Park, goats were introduced in the 1920s, before the park was established, for hunting. Park researchers subsequently discovered they were harming the communities of high elevation plants that the goats were eating. Park wildlife managers started removing the animals in the 1980s, but the removal was halted after public outcry and a lawsuit.

Yellowstone has also seen nonnative goats immigrate to the park from more northern locations in Montana where they were introduced for hunting. Paul Schullery, a retired technical writer and historian for the Park Service who worked in Yellowstone, said people usually find the animals on the northeast edge of the park. However, goats are known to move into the interior of Yellowstone as well.

“I know that there have been sightings over the years on Mt. Washburn and Gibbon Canyon,” Schullery said. “This has been going on for at least 20 years.”

To date, Schullery said he is unaware of any concerted efforts to remove the species.

“It’s the usual issue for a national park,” he said. “Their legislative mandates are pretty clear: nonnative species are not generally welcome. But, in the eyes of your constituents, they’re [likely] to be much more enthusiastic if you’re fighting spotted knapweed than if you’re fighting truly a glamorous mammal [such as a mountain goat].”

Schullery and Cain agreed that mountain goats aren’t native to the region. “After a lot of homework ... there’s no meaningful evidence that goats were in Greater Yellowstone,” Schullery said.

Cain said there is some evidence of a primitive goat that inhabited the region before the last ice age, but most scientists agree that would not make modern mountain goats native to the region.

“Our National Park Service policies revolve around the maintenance of native species in approximately the same numbers and distribution that existed prior to European settlement, with a strong emphasis on natural ecosystem functioning,” Cain said. “We know that mountain goats are a nonnative species. They do not fit into a natural ecosystem function in the Teton Range.”

Beyond the policy implications, Cain said the biggest concern is the mountain goat’s impact on bighorn sheep habitat, although he said there is disagreement among scientists about whether goats are true competitors with sheep. Cain said that the transmission of diseases from goat to sheep isn’t a big concern, but competition for food could hurt the sheep herd.

“Given ... that our bighorn sheep herd is threatened by many other challenges, we’re concerned that adding an additional challenge such as mountain goats could be the straw that breaks the camel’s back in terms of the bighorn sheep herd’s long-term persistence.”