Add to that the populations of northern Siberia and the Laplanders whose diet and life support systems consist almost entirely of one single animal:
Rudolph!
Some limited fish and seal, but not much.
The reindeer are the only large animal that can eke out an existence from the lichens and very sparse vegetation.
They eat the plants.
The people eat the reindeer.
And let's not forget the Plains Indians before white settlers came. There's not much on the plains but grass and buffalo. The buffalo ate the grass and the Indians ate the buffalo.
Environmentally-correct education bemoans the "senseless slaughter" of the buffalo herds when the white man came, but there was a very rational purpose behind it. The Indians were nomadic and very hard for the US Cavalry to track down, and could put up a fight when they WERE found, as General Custer discovered. But the Indians could not survive without buffalo, so if you want to get rid of the Indians, the simplest method was to get rid of the buffalo.