The end of the last glacial stage (10000 — 800 BC) was the result of a sudden warming. America's great predators disappeared (American lions, giant bears, sabre-toothed tigers smilodon). The modern bison appeared at that time, the result from a possible crossbreeding between the bison occidentalis and the bison antiquus.

The territories, freed from the ice, became huge pastures. Bison occupied this territory and bred in a spectacular way (according to estimates, there were approximately 30 to 75 million heads in the 1800s).

With the arrival of the Europeans, bison were slowly exterminated until the end of the 1800s, this period coinciding with the colonization of the West and the arrival of the railroad. In the face of these modern predators, the American bison came close to extinction, plummeting to 1,500 heads at the turn of the century.

The Canadian and American governments adopted protective measures which allowed the species to reappear slowly in both countrie's national parks. We estimate that about 50,000 bisons roam freely today. At the beginning of year 2000, the number of bison in private ranching facilities was about 300,000).