Even a casual look at a bison skull reveals the animal's large molars. These chewing teeth are adapted to a grazing lifestyle--bison feed predominantly on grasses--and are high-crowned, as lifelong use wears them down.
Tendons at the back of the skull affix to the bison's hefty "vertebral processes," which are extensions of bone along the vertebrae that help distribute the weight of that big head to the powerful shoulders.
Both bull and cow bison have horns, though they are larger in the males. The outer portion of the horn is a sheath of keratin (the same material as in your fingernails), while bone composes their inner core, attached to the skull. The horns grow throughout the bison's lifespan -- first out, then up, and eventually turning inward.
Across most of their range, bison must contend with ferocious winters. They use those tremendous head and shoulder muscles to sweep their foreheads through snow drifts to expose forage below.
Like some other bovids, bison have well-developed frontal sinuses to protect their brain during the head-butting battles that sometimes result from dominance standoffs. Bulls are the main fighters, squaring off during late-summer rut.
