Monitoring Abundance, Recruitment and Range Expansion

During the 1990s, descendants of mountain goats introduced into Montana during the 1940s and 1950s colonized the northeast and northwest portions of the park via the Absaroka and Gallatin mountain ranges. This colonization raised concerns about adverse effects to native bighorn sheep, rare plants, and alpine habitats. Investigations of paleontological, archeological, and historical records have not uncovered evidence that mountain goats are native to the Greater Yellowstone Ecosystem.

We collaborate with the Montana Department of Fish, Wildlife and Parks to conduct aerial survey flights every one to two years that (1) estimate the distribution of mountain goats within and adjacent to the park, and (2) classify a representative sample of the population to obtain an index of recruitment (i.e., kid:adult ratio). Aerial counts of mountain goats inside or within one kilometer of the park increased from 24 to 178 from 1997 to 2009. Mountain goats have established a breeding population in the park and are at relatively high abundance in the northeastern and northwestern portions. Sustained colonization of suitable habitats south of The Thunderer and along the eastern park boundary has not yet occurred, but sporadic observations of females with young-of-the-year suggest that colonization of this area may eventually occur. We estimate that 200-300 goats are present in or adjacent to the park.

Updated 7/19/10