METHODS 



The bison reduction provided the opportunity to collect 

 data on a large proportion of the animals that were harvested. 



Bison were field aged by examining incisor and canine teeth 

 for eruption and replacement (Hogben 1980, Prison and Reher 

 1970, Fuller 1959) through age class 5. Wear of permanent 

 incisors and canine tee^h was examined for all older ages. 



Physical size, shape of horns, and number of horn rings 

 provided another confidence indicator of age groups for both 

 sexes . 



Teeth were obtained for cementura ages in the field or by 

 mail request after bison removal. Cementum ages were assigned 

 by Matson's Laboratory in Milltown, Montana, using criteria 

 described by Armstrong (1965) and Novakowski (1965). When 

 possible, the first incisor (I,) was sectioned to determine 

 cementum annuli. If (I,) was unavailable, other teeth were 

 used. 



A modified age was assigned under the following 

 circumstances. The age determined by either cementum annuli 

 or in the field was used when that was the only age available. 

 If both cementum and field ages were available for an 

 individual animal and they did not agree, they were handled as 

 follows : 



1. If there was only one year difference, the field age 

 was used for ages < 7 years, while the cementum age was 

 used for ages 7 and over. 



2. If the difference was greater than one year, an 

 average of the ages obtained by the two methods was used. 



Sex of animals and the pregnancy status of females were 

 determined in the field when animals were eviscerated. 

 Fetuses were collected and frozen for later measurement at the 

 MDFWP Wildlife laboratory in Bozeman. Weight, crown-rump 

 length, and sex were recorded for all fetuses. 



Blood was collected by individual hunters and by MDFWP 

 officials and the serum was analyzed for the presence of 

 brucella antibodies by the Montana Veterinary Diagnostic 

 Laboratory, Bozeman, MT. , using standard laboratory procedures 



(NADL 1967) . 



