Bison face a significant threat from humans hunting their populations through selective harvesting or trophy hunting. Although the effects of hunting on the demography of bison is thoroughly documented, the effects on the behavior of surviving bison are not known to the same degree. In North American plains bison, ‘bellows’ are categorized as low, guttural vocalizations made by bulls during the breeding season in competitions between males. One critical area of bison behavior that hunting could affect is formant frequencies, which are peaks with a higher degree of energy. Vocal tract dimensions determine formant frequencies, and longer vocal tracts produce lower frequencies. They can be reliable indicators of body size and other important traits for mating selection. In this study, we analyzed samples of bison recordings from various locations, with hunting and without, throughout the Midwest. We recorded bison bellows from 9 locations and then analyzed each bellow to obtain the first 6 formants. Using a test of normality the formant frequencies were found to be not normally distributed for all formants. Further data analysis has shown that frequencies are lower in sites without hunting and higher in locations with hunting for the first formant. We predict that this pattern will be seen through out the remaining formants. These results would indicate that hunting may cause smaller body sizes in males and impact the health of the surviving bison, which could negatively affect the demographics of their population. Size and health are an important factor for mating selection and understanding how hunting impacts the surviving bison is crucial to stabilizing and protecting bison populations.