Researchers have for the first time witnessed the death of a female orangutan at the hands of another female. Even more extraordinary is that the perpetrator recruited a male orangutan as a hired gun to help her corner and attack the victim. Before this observation, lethal fights between females had never been observed in orangutans; in other primates such fights occur mainly between males, according to Anna Marzec of the University of Zurich in Switzerland. She is the lead author of a report on the fatal incident, which appears in Springer's journal Behavioral Ecology and Sociobiology.

Aggression serves ultimately to gain access to limited resources. Although aggression among primates is frequent, lethal attacks are very rare, especially among female individuals. Female Bornean orangutans live alone and typically settle in or near the area where they were born, whereas males generally disperse. The two sexes regularly associate only during the few months before a female orangutan is