sheep were o^^served, followed by 76 in March, 74 in April, 46 in May, 

 and 35 in June. These figures represent the maximum number of sheep 

 observed during any one census. Observability of sheep was hampered by 

 dense timber, rugged terrain, and ground censusing from one elevation 

 along the highway. Aerial surveys vere limited due to dangerous flying 

 conditions in the narrow canyon. A capture and mark program would be 

 necessary to obtain population estimates or year}y trends. 



Bighorn ewes do not normally breed until 2.5 years of age (Smith 

 1954). It was difficult to separate the yearling ewe component and the 

 1/2 to 3/4 year old rams from adult ewes depending upon the date of 

 observation. The unclassified portion of the herd consisted of this 

 faction and possibly some adult ewes. Sheep classified as lambs in 

 April were considered yearlings in May, since two newborn lambs were 

 observed May 7. The lamb/ewe ratio (primary age ratio) based on classified 

 animals for the February through April period was 50.5/100. This figure 

 may be high if adult ewes were inadvertently unclassified. The ratio is 

 39.4/100 when the unclassified segment is incorporated. The true primary 

 age ratio falls within this range (11 percent). Stelfox (1976) indicates 

 that the average primary age ratio of four Canadian bighorn herds during 

 the winter period was 45.6 lambs/100 ewes, which compares closely with 

 these findings; however Brown (1974) found an 82 percent ratio for the 

 February through April period in the nearby Thompson Falls herd. Age 

 ratios cannot be used to interpret herd vigor (Caughley 1974) because 

 the population may be exploding or crashing while the age ratio is doing 

 the opposite, depending upon other demographic factors. The 1978 ram/ewe 

 ratio for all months combined was 36.8/100. During a May 3, 1979, 

 helicopter survey of the Kootenai Falls area, MDFWP personnel observed 

 80 sheep and obtained ratios of 33 lambs: 100 ewes and 58 rams: 100 ewes 

 (Weckwerth et al. 1979). 



The activity or behavior of all observed bighorns was recorded 

 according to one of five activity patterns (Table 15). Seasonal changes 

 did not seem to influence activities, although walking and running were 

 observed more often during the summer months. The sheep observed showed 

 no apparent reaction to the presence of train work crews or other human 

 presence on the south side of the river. Trains pass through the area 

 fairly regularly and the sheep are probably habituated to the noise 

 created. Highway 2 is clearly visible from the north bluffs, but auto 

 traffic had no apparent effect on the sheep. 



Habitat use on the Kootenai Falls bighorn sheep range is summarized 

 in Tables 16 through 20. As previously mentioned, an observability bias 

 was present which likely influenced the data. A radio-tracking program 

 would be necessary to alleviate this type of bias. Table 16 and Figure 8 

 reveal where bighorns were observed, by season. From November through 

 March, most bighorns were observed from just below the Falls (area 3), 

 across Kootenai Mountain (areas 1 and 2). During spring and summer 

 (except for June) the majority of sheep were found on other portions of 

 the study area, upriver from the Falls. During November through March 

 the majority of sheep were observed using the broken terrain type (Table 17) 



58 



