Form a paper in Nature:
Noë, a primate behavioural ecologist now at the Hubert Curien Multidisciplinary Institute in Strasbourg, France, had come up with a biological market-based theory of cooperation. It proposed that animals cooperate to trade a specific commodity — such as food — for a service that would promote their survival, such as protection from a predator.
‘Cleaner’ fish, such as the brightly striped wrasse, will nibble parasites off the skin of ‘client’ fish in small coral territories known as cleaning stations…
While racking up evidence for the market theory, Bshary also observed a range of other social behaviours that had never been seen before in fish. He saw that unsatisfied clients sometimes punish cheating cleaners by chasing them around, and that this punishment makes these fish less likely to cheat. He saw cleaners ingratiating themselves with certain clients: they gave preference to visiting fish such as groupers, rather than the smaller, local fish that did not have the option of going elsewhere. He found that the cleaners cheated less when they were being watched by other potential clients — a sign that they were buffing their reputations. And he saw reconciliation: if cleaners behaved badly, they then massaged the backs of offended clients with their pelvic fins.
As Tyler Cowen says, Markets in everything.