There was a time when the prairies of North America trembled as they passed: tens of millions of bison, in herds that took days to go by. At the end of the 19th century, mass hunting left only a few hundred in the wild. Today their recovery is a symbol, and it is the national mammal of the United States. The bison is the largest land mammal in North America: a male can weigh almost a ton. Its hump is pure muscle, and it uses it to swing its head like a shovel and push aside the snow in winter. It looks heavy, but it runs at more than fifty kilometers per hour and clears fences of almost two meters. A tip from those who know it best: if it raises its tail, keep your distance.