First Bison Calf
The gestation period for the American bison is 9 1/2 months. Under normal conditions, cows have their calves from mid-April through June. Cows generally have one calf per year, but twins may occur very rarely.Calves are born big.
American bison calves weigh a massive 30 to 70 lbs. at birth, according to the U.S. Department of Interior. A calf is protected not only by its mother, but also by the whole herd. They are weaned at 7 to 13 months and typically become sexually mature at 2 to 3 years of age.