Email
PrintMystery Of The High Lonesome
Isolated Teton Range bighorn sheep herd has researchers scratching their heads.
Field technician Marci Trana hikes across Owl Peak in the northern Teton Range in summer 2010 to retrieve a bighorn sheep GPS collar.
(page 1 of 7)
Four days before Christmas 2008, Rocky Mountain bighorn sheep No. 753 stood just below the 11,100-foot summit of Prospectors Mountain as the temperature dropped to twenty-five degrees below zero.
Most of the winter and spring 753 spends above tree line eking out a living. She depends largely on the fat she’s stored from grazing during the summer and fall, supplemented by whatever grasses and lichens she can find on the south facing, windblown, high-elevation slopes where she lives. Though the rams of the herd impregnate her almost every year, very few lambs survive their first winter. Starvation and exposure are the most likely causes of death.
Such is the existence of the Teton Range Bighorn Sheep Herd, a group of about 150 sheep that Wyoming Game and Fish officials have called the most threatened ungulate population in the region. Unlike other bighorns that migrate down to friendlier habitat in the winter, these sheep live high among the peaks of the Tetons year-round. In addition to starvation and exposure, avalanches constitute a significant cause of mortality. This extreme lifestyle, coupled with their small herd size and nearly total isolation, mean inbreeding, disease, or a particularly bad bout of weather could wink the herd out of existence.
The high-elevation nature of the herd’s habitat also means the Teton sheep are hard to study. Researchers can only guess at how they survive in a climate that, in winter, is manageable only by the hardiest species of flora and fauna, such as whitebark pine and the wolverine. Basic facts about the bighorn herd’s reproduction, distribution, and habitat use are vague guesses at best; scientists aren’t even sure what they eat.
To answer those questions, researchers with the Wyoming Game and Fish Department, Grand Teton National Park, the Bridger-Teton National Forest, and other agencies enlisted the help of University of Wyoming graduate student Alyson Courtemanch. The researchers used a helicopter and net guns to capture twenty-eight bighorn sheep, all females, and fitted them with hybrid radio/Global Positioning System collars. The GPS part of the collar recorded five locations a day for each ewe, while the radio collar helped the researchers locate the animals during the study and retrieve the collars once they fell off as programmed at midnight on July 5th, 2010.
