Age structure of female (Appendices E and F) and male 

 bison (Appendices G and H ) indicated more males in the younger 

 age classes (1-4 years) and more females in the mature age 

 classes (5-9 years). Similar numbers of both sexes were 

 recorded in the older ace classes (10-15 years), but the two 

 oldest animals (15 years) were both females. Old age in bison 

 has been documented at 12-15 years (Fuller 1959) with an 

 occasional animal reaching 20 years (Meagher 1973) . 



Percentages of calves, yearlings, 2H year olds, 3^ year 

 olds, and adults in 1964-65 (Meagher 1973) were 19, 14, 6, 11, 

 and 49, respectively. In 1988-89, the percentages were 14, 



14, 13, 14, and 45, for the same age classes, respectively. 



AGE STRUCTURE BY BRUCELLOSIS TEST RESULTS 



Age structure of animals by sex and brucellosis test 

 result is presented in Table 5. Age structure of females 

 testing negative for brucellosis versus females testing 

 positive were statistically similar (p<0.05). Male age 

 structures were also similar between reactive and non-reactive 

 animals (p>0.05). There was no difference between reactive 

 and non-reactive male age structures compared to reactive and 

 non-reactive female age structures (p>0.05). This shows 

 strong conf irm.ation that the brucellosis organism does not 

 preferentially infect any age group. 



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