New research suggests that backcountry skiers may be pushing endangered big horn sheep from their winter habitat in California’s Sierra Nevada Mountains. These findings were presented at The Wildlife Society’s 2022 Annual Conference in November and reported this week on the conservation organization’s website.

The study was conducted by Jaron Kolek, a University of Wyoming graduate student who examines human-wildlife interactions. A longtime outdoorsman who enjoys mountain biking, rock climbing, backcountry snowboarding, and backpacking, he began to wonder how these activities—generally considered “low impact”—were affecting wildlife.

Focusing on Sierra Nevada bighorns, a subspecies of bighorn sheep considered endangered by the U.S. Fish and Wildlife Service, Kolek used data from GPS collars that the California Department of Fish and Wildlife fitted on the sheep from 2013 to 2022 in the northernmost end of their range, between the town of Lee Vining and Yosemite National Park.

That area is also a hotspot for backcountry skiers. Kolek used data generated by Strava, a fitness app that allows users to plan and record their workouts. Strava’s mapping function allowed Kolek and his research partners to see skiers’ routes across the season and pinpoint activity hotspots.

bighorn sheep walk across snowy landscape
Sierra Nevada bighorns are a distinct species of bighorn sheep. Steve Yeager / NPS

Comparing the two data sets, Kolek found that bighorns initially set up their home ranges close to the areas favored by skiers, but they changed their habitat use during ski season to avoid human activity. The forced movement, he hypothesizes, may cause the sheep to burn through fat reserves and winter in areas with poorer-quality habitat.

The pressure that humans put on game animals while hunting and shed hunting, of course, has long been a factor in the decisions made by wildlife managers. Just this spring, officials in Utah and Wyoming pushed back antler-collecting seasons over concerns that mule deer, elk and other big game stressed by a harsh winter and above-average snowpack might be pushed to the breaking point by an influx of shed hunters.

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With increasing research showing that so-called “non-consumptive” outdoor activities like winter sports and other types of tourism can also have a notable effect on wildlife, some scientists and conservation leaders are arguing that those uses need to be taken into greater consideration for wildlife management decisions, especially during unusually harsh winters.