Descendants of mountain goats (Oreamnos americanus) introduced in the Absaroka and Madison mountain ranges during the 1940s and 1950s established a population in Yellowstone National Park in the 1990s. They have reached a relatively high abundance in the northeastern and northwestern portions of the park. Investigations of paleontological, archeological, and historical records have not found evidence that the mountain goat is native to Greater Yellowstone.
Many people consider the goats a charismatic component of the ecosystem, including those who value the challenge of hunting them outside the park. But the colonization has raised concerns about the goats’ effects on alpine habitats. Competition with high densities of mountain goats could also negatively affect bighorn sheep, whose range overlaps that of mountain goats.
Mountain goats live in alpine habitats. Studies of alpine vegetation in the northeast portion of the park during 2002 and 2003 suggest that ridge-top vegetation cover is lower, and barren areas along alpine ridges are more prevalent in areas that have received relatively high goat use. Studies by Idaho State University and the National Park Service during 2008–2010 suggest goats are affecting the soil chemistry of sites they inhabit by increasing the availability of soil nitrogen through deposition of urine and feces. Soil rockiness may be increasing slightly over time at sites with high goat presence, but no largescale effects have been detected so far with respect to vegetation (species, community structure).
Colonization of suitable habitats south of The Thunderer and along the eastern park boundary within the Absaroka Mountain Range appears to be occurring, with a larger number of groups with females and young observed on Saddle Mountain and on Castor and Pollux peaks during recent years. Mountain goats have not been surveyed in the park since 2014 due to both poor flying conditions for survey aircraft and budgetary constraints.
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Yellowstone is being invaded by mounain goats. This non-native species poses a threat to Yellowstone's alpine as well as bighorn sheep.
Flesch, E. P. and Garrot, R.A. et al. Range expansion and population growth of non-native mountain goats in the Greater Yellowstone Area: Challenges for management. Wildlife Society Bulletin 40(2):241–250.
Laundré; 1990. The status, distribution, and management of mountain goats in the Greater Yellowstone Ecosystem, final report. Pocatello, ID: Idaho State University, Department of Biological Sciences.
J.W., Lemke 2004. Origin, expansion, and status of mountain goats in Yellowstone National Park. Wildlife Society Bulletin 32(2):532–541.
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