When Pike reached the country the herds were going south from the Platte towards their wintering grounds below the Arkansas.

At first he passed through nothing but droves of bulls.

It was not until he was well towards the mountains that he came upon great herds of cows.
Other Game.
The prairie was dotted over with innumerable antelope.

These have always been beasts of the open country; but the elk, once so plentiful in the great eastern forests, and even now plentiful in parts of the Rockies, then also abounded on the plains, where there was not a tree of any kind, save the few twisted and wind-beaten cottonwoods that here and there, in sheltered places fringed the banks of the rivers.
Indians Hunting.
Lewis and Clark had seen the Mandan horsemen surround the buffalo herds and kill the great clumsy beasts with their arrows.

Pike records with the utmost interest how he saw a band of Pawnees in similar fashion slaughter a great gang of elk, and he dwells with admiration on the training of the horses, the wonderful horsemanship of the naked warriors, and their skill in the use of bow and spear.