Only humans and a handful of other primates will attempt to make peace between warring third parties. But now there is a new diplomat on the block: the cleaner wrasse. Cleaner wrasse (Labroides dimidiatus) feed on the parasites that attach themselves to the outsides of other fish, and even throw in a calming massage with their pectoral fins. In return for the services, client fish don’t attack their cleaners and return regularly to their territories to supply them with more food.
The cleaner-fish scenario is a textbook example of mutualism, in which each species benefits, but ecologist Karen Cheney at the University of Queensland, Australia, suspected that there was more to it. Cheney had seen little evidence of aggression between reef-fish clients at cleaning stations and few instances of predation. Fish also often stayed inside cleaner territories long after the cleaning was over, suggesting that the territories could be functioning as a safe haven.