population age structure described by Cowan and Geist (1971), 

 determined a fall population of 100 bighorn sheep of all ages and 

 both sexes was required to yield an average of four to five legal 

 (three-quarter curl) rams annually. Ihis is roughly one legal ram 

 per 25 bighorn sheep. Using this assumption and the harvest esti- 

 mates for 1954 through 1973, the minimum population based on 100 

 percent harvest of all legal rams was plotted (Line B, Figure 2). 

 During the early 1960's, three Boone and Crockett rams were har- 

 vested from the Ural-Tweed population indicating all the legal rams 

 were not being harvested each year. Since a 100 percent harvest of 

 the legal rams was not occurring, the estimates based on the har- 

 vest are absolute minimum population levels. 



During the period of 1954 through 1966 up to 30 permits 

 (three-quarter curl rams) were issued for the Kootenai area with a 

 maximum harvest of 10 rams (six from the Ural-Tweed), with an 

 average hunter success of 28.4 percent ( Mont, Dep. Fish, Wildl. 

 and Parks, unpubl. files). The estimates of 320-460 bighorn sheep 

 presented by the Montana Department of Fish and Game and U.S. 

 Forest Service for the Ural-Tweed population should have produced 

 at least 13-22 legal rams annually. If this number of legal rams 

 were available, the annual hunter harvest should have been greater. 

 Therefore, a population level in the vicinity of 150-200 bighorn 

 sheep was considered to be more reasonable. This population level 

 corresponds favorably with the population estimate of 170 sheep 

 within the area of influence (U.S. Dep. Inter. 1965). 



4) Assessment of Impacts 



The population decline resulted from the cumulative impacts of 

 at least two events: 1) ecological succession from an open bunch- 

 grass - ponderosa pine disclimax to a more closed Douglas-fir com- 

 munity, and 2) construction of the Libby Dam project and associated 

 facilities, including relocation of Highway 37 through the bighorn 

 sheep range. 



Three studies conducted on the Ural-Tweed range all determined 

 the sheep preferred the open bunchgrass communities with scattered, 

 open stands of timber - ponderosa pine and Douglas-fir (Ensign 1937, 

 Brink 1941, Brown 1979). These compare favorably to studies con- 

 ducted on other bighorn populations (Couey 1950, Smith 1954, Geist 

 1971). The quality of the Ural-Tweed range for bighorn sheep has 

 historically been maintained by fire which produced the open bunch- 

 grass communities. This is documented by the abundance of fire 

 scarred trees in the area (Brown 1979) and through aerial photos 

 taken in 1949 which show the presence of numerous fires in the area 

 adjacent to the Kootenai River. However, with the initiation of 

 intensive fire suppression in the 1930's, the role of fire in main- 

 taining the preferred ecological disclimax was circumvented and more 

 densely forested Douglas-fir communities became established on once 

 quality bighorn sheep habitat. A summarization of the incidence of 

 fire in the area between 1940 and 1977 (Brown 1979) illustrates the 

 active fire suppression policy inacted throughout the area (i^pendix 



33 



