Researchers have witnessed for the first time a female orangutan kill another female. Not only that, but the perpetrator of the attack was backed up by a male, who seemed not only to engage in the fight but also to block the victim's exit. The conflict was only broken up when a second male came on the scene and escorted the injured female away. But unfortunately, even this intervention wasn’t enough to save her as she died two weeks later from her wounds. The extraordinary event has been documented in a paper published in Behavioral Ecology and Sociobiology. 
The attack took place in the forests of Borneo, where most of the world’s remaining orangutans reside. While red apes live relatively solitary lives, the females do live in overlapping ranges that are patrolled by one resident and other roaming males. Aggression is known to occur within the species, with males being recorded raping females, and unrelated females fighting when they come into contact. But attacks leading to severe injuries, and eventually death, had never before been observed between females.
This particular case, which occurred in 2014, involved two orangutans that have been subject to observations by researchers from the University of Zurich for the last 13 years. The incident involved a young female called Kondor, who had just lost an infant, and a much older ape known as Sidony. The two females had fought before, when Kondor tried to approach Sidony’s daughter, but that was a few years ago.
This time, Kondor was found with a male known as Ekko. The pair came across Sidony and her son, and Ekko started to sexually inspect the older female. Ekko then returned to Kondor and they started mating – that is until Sidony tried to move away from the copulating pair, at which point Kondor broke up the sex and violently attacked Sidony. It was then that Ekko joined in the fight, backing up Kondor as she bit and hit the older female, and blocking her route so she couldn’t escape. With his large canines, Ekko was seen inflicting serious damage to Sidony.
Male orangutans with their distinctive facial flanges are much bigger, and thus much stronger, than the females. Sergey Uryadnikov/Shutterstock
But it didn’t end with that, as a second male ape then entered the fray, known to the researchers as Guapo. He successfully managed to scare off Ekko, before turning his attention to Sidony, with whom he mated, even as Kondor continued to try and harass the older female. Eventually, Guapo positioned himself in between the two fighting apes, before escorting Sidony away. Unfortunately though, this intervention proved to be too little too late, and Sidony died from her injuries two weeks later.
While primates are known to show lethal aggression towards each other, this is normally limited to male-male conflict, and only rarely spills over into female conflict. Chimpanzee females have been known, for example, to kill other females’ infants. But this is the first time such deadly aggression has been seen among female orangutans, and even more interestingly, the recruitment of a male in order to help their cause.
Image in text: Female orangutans look after their offspring for extended periods of time, and are only ready to conceive about once every seven years. Sergey Uryadnikov/Shutterstock
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