Territorial aggressions and instigating trespasses pay off among chimpanzees

Many animals cooperate with group members because what they can achieve by working together exceeds what they can obtain on their own. Chimpanzees, for example, are patrolling their territory and trespass into enemy territory. If they meet rivals, they attack and sometimes kill them. Researchers of Arizona State University have now found that it pays off for the animals to take this risk: In the long run they protect their group and increase its size. Linda Vigilant of the Max Planck Institute for Evolutionary Anthroplogy contributed to the study by analyzing the chimpanzees' family relationships.