Bison

Estimates of the prehistoric numbers of bison on the American plains, before the arrival of Europeans, vary from 30-80 million. At the time, bison were a "pantry on the hoof" for the Plains tribes of Native Americans, who used the animals for food, clothing, fuel, and shelter, killing only what they needed to survive.

Bison herds move around constantly in search of food and water, and typically travel several miles a day. Unlike many migrating animals, bison do not follow set paths each year, and even minor stimuli can change their direction of travel. This might be a strange scent in the wind, an unfamiliar animal crossing their path, or a dried-up water hole. The only set pattern to their migration is that they meander north to find a good place to raise their young in the summer, and then south to ride out the winter. The herd follows experienced, lead animals. Bison in herds continually make noises to each other, using roars, grunts, sneezing, snorts, and bawling to communicate different meanings.

The least hint of danger can set a herd stampeding across the prairie. The stampede speed may reach 35 mph (56 kph), though they cannot keep that speed up for more than about half an hour. If running does not shake their pursuers, bison may turn abruptly and charge. The animal's skull in the forehead is double-thick, protecting the brain from damage during impact.