From Yellowstone Wildlife: A Watchers Guide
by Todd Wilkinson.
From any vantage point within Yellowstone, mountains are visible on the horizon. The park would therefore seem an excellent place to find billies and nannies, which occupy other high-elevation wildlands such Glacier National Park. In fact, though, mountain goats (Oreamnos americanus) are only occasionally seen in the high peaks of the park's northwest and northeast corners.
According to fossil remains found at Palisades Reservoir in Idaho and at Pleistocene sites south and east of Yellowstone, goats may have lived near the park about 10,000 years ago, but then dispersed. For hunting purposes, these light-hooved alpinists were transplanted to areas near the park a number of years ago. Some descendants of those transplants have begun migrating into Yellowstone-a migration that the National Park Service regards as "artificial."
"During the past 30 years, one to fifteen goats have been reported at least seventeen times in the park, and on five occasions near the park. Of the seventeen in-park observations, six were in the northwest corner and eleven were in the northeast corner of the park," wrote research interpreter Norm Bishop in 1990.
The mountain goats are squarish and sure-footed, with long, yellowish-white fur and black, spiked horns. Males stand about 3 1/2 feet high and weigh between 120 and 250 pounds, while the females, which also have horns, are slightly smaller. Check the difference between white mountain goats and pale, female bighorn sheep before you conclude that you have seen a goat.
Seeing a goat from the highway is a rare event. The northeast corner of the park, on the cliffs emanating from Baronnede Peak (north of the highway) and Abiather Peak (south of the highway), provides the best opportunity.
If you see a goat, write down the location and report it to a park ranger. In recent years, natural colonization (migration consistent with historical movement) of the park by mountain goats has occurred in the rocky canyons along U.S. Highway 191 (the far northwest corner of Yellowstone). Those goats will be allowed to repopulate the park because the colonization is considered consistent with the natural expansion of game territories as defined by the National Park Service's "natural regulation" policy.
The "artificial" population of goats invading Yellowstone from the northeast, however, may be prevented from establishing a niche here if it poses a threat to native vegetation and habitat important to the bighorn sheep. Continue to the next page, Mule Deer.