As any schoolkid in the playground can tell you, fights don't just involve those trading blows, but those watching too. Like spies, these bystanders observe, obtaining useful information about the individuals in the fight that they may be able to use to their advantage in future aggressive situations.
Biologists interested in aggression have previously reported that animals also "eavesdrop" when fights occur, and use the information in the future. Now, an evolutionary biologist from the University of Cambridge, Rufus Johnstone, has made a mathematical model of fighting that allows the possibility of eavesdropping. His paper was published Wednesday in the journal Proceedings of the National Academy of Sciences.
Johnstone was aware of some elegant experiments on Siamese fighting fish by Peter McGregor of the University of Copenhagen. Watching the fish doing what they're named for, McGregor noticed that other fish in the tank were hanging around watching the fight, like spectators at a boxing ring. When McGregor set up fights between bystander fish and contestants, he found that bystanders were wary -- they took four times longer to approach the winner of the fight they'd just seen than they did to approach the loser.