A female American bison is known as a "cow." After competition between males, the cows mate with the "bulls" during the summer and are pregnant until the following mid-spring when they give birth to usually just a single "calf" of approximately 50 pounds bearing reddish fur.
Like male bison, females also have short, curved black horns that grow to about 2 feet in length. However, females are noticeably smaller than their male counterparts. While bulls may grow to a size upwards of 2,000 pounds and stand more than 6 feet tall, mature cows weigh roughly half that and stand slightly shorter.