Animals show not only the individual differences which human beings do, one liking this game and another that, one being leader in the sport and another the follower, but also the greater differences which characterize races.

The Spaniards love the bull fight; other nations consider it repulsive, and take their fun in less brutal forms, although, perchance, they tolerate Rugby football! So the animals vary in their tastes, some playing incessantly at fighting, and so zealously as to injure one another, while others like the milder romp, and the game with flying leaves, rolling stones, or the incoming waves on the shore.
3.

Psychologically, the most interesting characteristic of animal, as of human, play is what is called the "make-believe" state of mind which enters into it.

If we consider our own sports we find that, in the midst of the game, we are in a condition of divided consciousness.
We indulge in the scheme of play, whatever it be, as if it were a real situation, at the same time preserving our sense that it is not real.
That is, we distinguish through it all the actual realities, but make the convention with our companions that for the time we will act together as if the playful situation were real.

With it there is a sense that it is a matter of voluntary indulgence that can stop at anytime; that the whole temporary illusion to which we submit is strictly our own doing, a job which we have "put up" on ourselves.
That is what is meant by make-believe.
Now it is clear that the animals have this sense of make-believe in their games both with other animals and with man.