Caribou-Targhee National Forest

Wildlife - Bighorn Sheep Populations and Habitat

Final Enviromental Impact Statement
1997 Revised Forest Plan
Targhee National Forest

Bighorn sheep are present in four areas of the Forest, with an estimated total population of 225 animals (AMS 1992).

Lemhi Mountains- These bighorn sheep are part of a population that includes the adjacent Challis N.F. Forty-one bighorn sheep were transplanted on the Challis N.F. side in two transplants occurring in 1983 and 1984. A helicopter survey conducted in 1988 by IDFG found 31 bighorns (14 ewes, 8 lambs, 9 rams). No hunt has been authorized on these sheep.

South Beaverhead Range- (also referred to as the southern Bitterroot Mountains or the Medicine Lodge areaForty-one bighorn sheep were introduced into the south Beaverhead Range in four transplants between 1976 and 1982.

This herd has not grown as expected. We do know that the transplanted bighorn sheep had lung worms at the time they were transplanted. A helicopter survey conducted in 1988 by IDFG found only 17 bighorns (13ewes, 3 lambs, 1 ram).

The ear tags or remains of several of the released sheep have been found since the releases, but mortality causes are unknown. No hunt has been authorized on these sheep. Monitoring of bighorn sheep through recording of ground observations has been done by the Dubois Ranger District and IDFG. The highest number recorded from ground observations was 37 animals (5 rams and 32 ewes and lambs) in October 1995.

The Dubois Ranger District has implemented several habitat projects for bighorns in the south Beaverhead Range. Seven water developments, three which are in cooperation with the Foundation for North American Wild Sheep, have been installed for bighorns. Other water developments for upland game, deer, and elk on Forest Service and BLM lands are used by bighorns on transition range. Prescribed burns have been done to reduce sagebrush density and improve forage quality for bighorns.

All of the winter observations we know about have been on the Birch Creek side of the mountain range (We are not aware of observations in the Nicholia, Chandler, Kelly and Snakey drainages during the winter).

Lionhead Area- These bighorn sheep are part of a population that includes the Gallatin N.F. in Montana. During the summer and fall months, twelve to fifteen sheep can frequently be seen in Idaho. Idaho has never authorized a hunt on this herd. Montana has authorized hunts on this population.

This sheep population winters on high elevation windswept ridges. There is historical low elevation winter range available, but the sheep do not use it. In the early 1990's the Montana Department of Fish, Wildlife, and Parks introduced bighorn sheep into the low elevation winter range, hoping they would associate with the bighorns at the higher elevations during the summer, and re-establish the migration to the low winter ranges. This has not happened; the introduced bighorns have remained at the low elevations year-around.

Westslope of the Tetons- These bighorn sheep are part of a population that includes GTNP. WGF authorizes a hunt for bighorns on the Forest; no bighorn sheep hunting is allowed in GTNP. A total of eleven rams were harvested from 1977 to 1986; no bighorns have been harvested during the hunt from 1987 to 1991.

Interviews with old timers who were familiar with the Teton Range suggest that the bighorn population may have declined to a low point in the 1930's and 1940's, with some recovery in numbers during subsequent years. Minimum counts of bighorn sheep (not necessarily based on full coverage of suitable habitat) have ranged from 39 to 97 since 1976. Whitfield (1983) believed that the total population approached 125 in 1981 and was static or declining. Annual winter counts and high winter mortality during the last two years indicate that the population may have declined substantially.

Winter range is one limiting factor for this bighorn sheep population. All of the bighorns are wintering at elevations above 9,000 ft. on windswept ridges. For the past eight to nine years, no bighorn sheep have been documented wintering on the Forest; all have been found wintering in GTNP.

Since 1994, GTNP has been doing a bighorn sheep study which involved radio-collaring and tracking. Movements during the winter were minimal, commonly with sheep located only a few hundred meters away from the previous location. Movements increased substantially in May when sheep commonly moved to lower elevations at the mouth of the canyons where snowmelt had occurred on the south and east exposures. Summer ranges consisted of upper-elevation grassy benches and ledges near cliff areas for escape.

USDA Forest Service - Caribou-Targhee National Forest
Last Modified: Tuesday, 25 September 2007 at 15:07:52 EDT