Keeping Track of Grand Teton National Park's Bighorn Sheep

Crews netted 20 bighorn sheep in Grand Teton National Park last week to fit them with radio collars to track their movements. Wildlife capture crewman, Wes Livingston, collects blood sample from a bighorn sheep ewe in the northern Teton Range. Photo by Mark Gocke, Wyoming Game and Fish Department

Tick off a list of Grand Teton National Park's wildlife and bison, elk, moose and bears come immediately to mind. Bighorn sheep? Not so quickly, but they're there.

To help wildlife biologists stay more on top of what those sheep are doing, the biologists bestowed 20 ewes with necklaces, er, radio collars, the other day. The collars, loaded with a GPS system, will enable the scientists to keep track of where the sheep wander.

The collars are programmed to periodically record vital location data as the bighorns move across their range throughout the year. After two years the collars will automatically drop off and biologists will then
recover the collars to download the data onto computers. That information is intended to provide detailed information about habitat selection, travel routes and other factors (i.e. lamb production and survival) that are critical to ensuring the long-term survival of this bighorn population.

The Teton Range bighorn sheep population is Wyoming’s smallest and most isolated native herd, numbering just 100-125 animals. Federal and state biologists have been concerned for many years about the long-term survival of this particular herd. Due to a loss of historic low-elevation winter range, the herd now lives year-round at high elevation in the Teton Range, where because of their small population they are vulnerable to a single event—disease, harsh winter weather or avalanches—that could quickly reduce their numbers and lead to potential extirpation of the herd.

Although broad-scale information is available about bighorn sheep seasonal distributions, further detailed information on habitat selection, travel routes and movements is urgently needed and critical to the herd’s long-term persistence.

The 20 ewes were captured last Thursday and Friday. Technicians netted the sheep from a helicopter and then fitted them with the collars. No injuries were reported, either to the sheep or the technicians. Agencies participating in the study include the National Park Service, the Bridger-Teton National Forest, the Caribou-Targhee National Forest, and the Wyoming Game and Fish Department.

Growing recognition of the questionable future for this bighorn sheep population led to the formation of a Teton Range Bighorn Sheep Working Group in 1990—a group comprised of representatives from Wyoming Game and Fish Department, Bridger-Teton and Caribou-Targhee national forests, and Grand Teton National Park, as well as several individuals with expertise in bighorn ecology who are affiliated with non-governmental organizations.

Previous efforts to improve the Teton Range herd’s survival included seasonal closures of sheep winter ranges to reduce disturbance impacts during an especially stressful time of year, and the retirement of domestic sheep allotments in forest locations on the western slopes of the Teton Range. Although progress has been made in reducing some of the threats to the long-term survival of Teton Range herd, uncertainties still remain regarding their current distribution, and whether bighorn sheep avoid areas of human activity. Consequently, there is a critical need to further assess habitat selection patterns and general population status of this isolated sheep herd.