Numbers of coyotes responding to the siren during summer 

 declined from 1972-1973 to a low in 1977 (Fig. 5.8). 

 Estimated coyote numbers increased from 1977 to 1984 and then 

 declined through 1986. Notably, and contrary to general 

 public perception, coyote populations on both areas declined 

 following the 1972 ban on the use of Compound 1080 for 

 predator control. 



Data on numbers of coyotes and the minimum number of 

 litters on the study area during summer was provided by a 

 combination of siren-answer and den area surveys (Pyrah 1984) . 

 Estimates for 1984-1986 may be low relative to prior years 

 because den area searches were less intensive. Thus, numbers 

 may not have declined to the degree indicated in Figure 5.9. 

 It is possible peak numbers were actually reached during 1984, 

 as indicated by siren-answers, and declined thereafter. 



Total numbers of coyotes on the area during 1977-1985 

 (Fig. 5.9) varied by 1.6 times from low to high, a difference 

 of 52 coyotes. That difference was mostly the result of 

 variation in pup production and survival . The number of 

 adults varied by 1.5 times from low to high, or 17 adults. 

 Because pups comprise about one-half to two-thirds of summer 

 coyote populations, it was not surprising that the minimum 

 number of litters each year varied in a similar manner as 

 total coyotes. 



150 i 



Total Number of Coyotes 

 Number of Litters 

 Number of Adult Coyotes 



Figure 5 . 9 



Number of coyotes and minimum number of coyote 

 litters estimated for the Missouri River Breaks 

 study area, 1977-1986, using a combination of 

 siren-answer and den area surveys. 



140 



