indicated that more cottontails were observed during winter 

 1982-83 than at any other time. 



350- 

 300- 

 250- 



• Jackrabbits 



— o..... Cottontails 



1976 1978 1980 1982 



Year 



1984 



1986 



Figure 5.11 



Number of jackrabbits and cottontail rabbits 

 observed on a headlight survey route on the 

 Missouri River Breaks study area during 

 summers 1976-1986. 



Coyote population levels may have been related to 

 availability of rodents and rabbits on the area although not 

 in a direct linear manner. Correlations between the siren- 

 answer index one year and prey populations the previous year 

 were significant, indicating that coyote populations increased 

 the year following increases in prey populations. Correlation 

 coefficients were 0.76 (P = 0.01) for coyote populations and 

 jackrabbit numbers, 0.70 (P = 0.03) for deer mice, and 0.78 (P 

 = 0.01) for an index combining jackrabbits, deer mice, and 

 microtines. The combined index was based on coyote food 

 habits (Hamlin et al . 1984); microtines were twice as 

 important as deer mice, and all mice were twice as important 

 as jackrabbits. The correlation coefficients were reduced by 

 data for 1985 and 1986 because coyote populations did not 

 decline as fast as prey populations. The relationship between 

 minimum number of coyote litters and the siren-answer index to 

 the alternate prey index is illustrated in Figure 5.12. 

 Minimum number of litters may have responded to microtine 

 populations more than other prey. 



142 



