Why did the population tend to return to a stable state of about 40 buffalo in many different situations?

Because if you had more room, the buffalo can roam around more for food and space so more can be produced.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.