INTRODUCTION 



In 1988-89 an opportunity arose to obtain physical 

 information on free-ranging bison (Bison bison) emigrating 

 from northern Yellowstone National Park (YNP) into southern 

 Montana. The data collected, which eventually represented 60% 

 of Yellowstone's northern bison herd, were thus available for 

 comparison with previous collections. The usual biases 

 associated with partial sampling was avoided because of the 

 high percentage of the herd actually examined. 



In 1985, the Montana Legislature designated bison as a 

 game animal and allowed the Montana Department of Fish, 

 Wildlife and Parks to use the public as a method of removing 

 bison which entered Montana from YNP. 



During the winter of 1988-89, large numbers of bison 

 crossed the northern boundary of YNP into Montana. During the 

 summer of 1988, National Park Service personnel recorded the 

 largest bison population within YNP in over a century. 

 Concurrently this was also a summer of severe drought and the 

 most extensive forest fires in YNP ' s recorded history. 



Bison leaving Yellowstone National Park and entering the 

 State of Montana can potentially infect livestock with 

 brucellosis (Davis et al. 1990). Montana cattle were 

 certified as brucellosis free in 1985, a status achieved only 

 through the investment of considerable time, money, and other 

 resources. 



Previous research on YNP bison has been presented by 

 Meagher (1973), McHugh (1958), Locker (1953), Tunnicliff and 

 Marsh (1935), and Rush (1932). 



Objectives of this project were to gather population data 

 from Yellowstone National Park bison harvested in Montana. 

 Major data sets include the following: 



1. Age and sex composition 



2. Incidence of Brucellosis seropositive 



3. Physical measurements 



4 . Reproductive parameters 



AREA OF HARVEST 





The bison reduction occurred primarily north o^ 

 Yellowstone National Park in an area of approximately 80 km 

 near Gardiner, Montana (Figure 1) . In addition, one animal 

 was killed near Cooke City, Montana, and two near West 

 Yellowstone, Montana. 



