SUN TZU, the 5th century BC Chinese tactician, wrote that knowing your enemy is the key to victory, and military manuals still echo his advice. But while this strategy might benefit individuals and armies, a fresh look at a model of animal behaviour shows that it鈥檚 disastrous for populations as a whole.
Rufus Johnstone of Cambridge University modified a classic model of animal aggression to include 鈥渆avesdroppers鈥� 鈥� animals that watch conflicts between other animals and use this to judge whether or not to fight when they come face to face with one of the combatants. Surprisingly, he has found that there is far more aggression in populations with eavesdroppers.
鈥淓avesdropping, which supposedly evolves for an individual to avoid conflict, ends up making life worse for the population as a whole,鈥� says Johnstone. John Maynard Smith of the University of Sussex, who devised the original model of aggressive behaviour 鈥� the 鈥渉awk-dove game鈥� 鈥� says of the new model, 鈥淚 think it is quite an ingenious, fruitful approach.鈥�
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Hawks tend to resort to violence, whereas doves back down when threatened. A population of doves gets along fine, but if an aggressive 鈥渉awk鈥� mutant appears, it will initially be at an advantage.
As the number of hawks increases, however, each one becomes more likely to encounter other hawks and get into fights in which they get hurt. So a balance between hawks and doves evolves. But in reality, Siamese fighting fish, for example, often watch encounters between others. If they have to confront an animal they saw win its last fight, they will play dove and give way. If they face a loser, they play hawk.
At first, eavesdroppers thrive in a pure hawk-dove population, because they can often predict what another animal will do. But as eavesdroppers become common, it becomes likely their bluff will be called. For instance, if two eavesdroppers that both lost their last conflicts face each other, they will both play hawk. 鈥淭hey can get into an escalated conflict,鈥� explains Johnstone.
The result, as Johnstone will report , is that the level of aggression is higher in a population that includes eavesdroppers than in a pure hawk-dove situation. 鈥淭he more accurate the eavesdropping, the worse off everyone is. Ignorance is bliss,鈥� says Johnstone.
