JACKSON, Wyo. (AP) -- Scientists say the roughly 100 animals that make up the Teton Range Bighorn Sheep Herd are nearing extinction and that's got researchers looking for ways to reduce risks for the isolated sheep.

The herd used to migrate every winter from the high peaks of the Tetons to lower, warmer climes. But biologist Aly Courtemanch says that migration stopped after about 1950, perhaps as human development and domestic sheep grazing increased in the lower elevations.

Courtemanch and other researchers are using GPS devices and the help of backcountry skiers to learn how the herd survives through harsh temperatures and sparse winter habitat.

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Information from: Jackson Hole News And Guide, http://www.jhnewsandguide.com

Copyright 2010 The AP.