Nonnative mountain goats expanding in Yellowstone

By Joshua Rapp Learn

©Jessie DeVoe

Goats are coming around the mountains of Yellowstone, according to a new study that shows the introduced animals have expanded their range in the area.

But the jury is still out on the verdict of whether this is good or bad for the ecosystems of the Greater Yellowstone Area (GYA), according to Elizabeth Flesch, a Ph.D. student at Montana State University and lead author of a recent study published in Wildlife Society Bulletin.

©Hollie Miyaski

©Hollie Miyaski

Mountain goats (Oreamnos americanus) were introduced to the northern GYA in the 1940s and 1950s and into the Palisades in the southern GYA in Idaho in the 1960s and 1970s.

Flesch, a member of The Wildlife Society, and other researchers used 136 survey counts and 6,701 location counts taken between 1947 and 2015 to track goat distribution. They found that in the northern end of the Yellowstone area, mountain goat range had dispersed around 30-50 miles from the original introduction sites. In the southern areas, where they were more recently introduced, goats have dispersed 18-24 miles.

In the areas where they were introduced earlier, Flesch said that the population is not expanding so much as in the southern areas. Overall, they estimated more than 2,500 goats currently lived in the GYA — a huge growth from the less than 200 that were originally released at all sites.

©Hollie Miyaski

©Hollie Miyaski

She says that the goats provide a mixed bag of benefits and problems. The goats are appreciated by tourists and hunters and may provide extra food resources for predators like wolves, bears, coyotes or even scavenging birds and other species.

But mountain goats could affect some native plants in sensitive alpine environments and disturb the soil.

The researchers also found that ranges of the goats and native bighorn sheep (Ovis canadensis) overlap at some points. The goats could compete with bighorns for resources and the possible transmission of disease.

But not much is yet known about these potential effects.

“Essentially more research is needed on the niche overlap between mountain goats and bighorn sheep,” Flesch said. “This is kind of a baseline study trying to conduct an assessment to what can happen.”

Joshua LearnJoshua Rapp Learn is a science writer at The Wildlife Society.

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