Correct and there are games that model that behavior, for instance iterated stag hunt[1]. This shows the benefits of cooperation for pack animals much more than the classic prisoner's dilemma. Of course you could construct a more detailed game that includes factors like defense and having a single leader that would be even closer to reality. The math behind game theory is right, its a question of whether we have chosen the right game to play.

[1] http://en.wikipedia.org/wiki/Stag_hunt