Are Dolphins Reciprocal Altruists?

We believe that when taken in its totality, the very scattered and often anecdotal literature on dolphins suggests the existence of a system based to a considerable degree on reciprocal altruism. The evidence of epimeletic behavior, though based wholly on anecdotes, is so common as to be overwhelming in its broad detail. The data on school structure, based on reliable marking studies at sea, clearly shows much fluidity of relationship, except in the larger dimorphic, polygynous species; but in both, intergeneric and interspecific cooperative behavior is clear. Reciprocal altruism carries with it the opportunity for the development of complicated social relationships involving, in addition to altruism, deceit, punishment of those who violate social rules, and complicated communication systems between school members. While we could cite isolated anecdotes supporting this or that development of these sorts, we prefer not to at this point, but instead to conclude that in dolphins we are surely dealing with complicated social systems whose outlines we are now just beginning to understand.