It has been known that killing within a community is rare in the population of chimpanzees, so when scientists discovered chimpanzees conspiring, beating, murdering and partially cannibalizing their former leader, they were completely shocked.
Science Alert noted that the researchers, led by anthropologist Jill Pruetz from Iowa State University, did not actually see the killing, which was recorded in Senegal in 2013, because it was dark, but they could hear the screams and calls during the deadly attack.
When they came back to the site the next morning, they were surprised to find that the group of chimpanzees is still beating the corpse, hitting it with sticks and stones and even biting off its flesh including its genitals.
The researchers spent years analyzing the footage which they took. They argue that the behavior of the chimpanzees to conspire to form a one group and target their alpha male, a 17-year-old chimp called Foudouko, is odd.
"It was very difficult and quite gruesome to watch," Pruetz in a statement. "I couldn't initially make sense of what was happening, and I didn't expect them to be so aggressive with the body."
Their study suggests that Foudouko, who was previously a tyrant, has been exiled for five years because he maintained an alliance with the beta male, Mamadou, who became weak and frail. Fouduoko was ostracized for it and then ousted by the others.
A few years later, he tried to get back on the group and claim his alpha male status back. While Mamadou and his brother (who has taken Foudouko's place), there were some who did not want him. As such, the killing occurred.
The group of young chimpanzees conspired to attack Foudouku. They abused and cannibalized his body for nearly four hours. There was also an indication that within the group, there were two that didn't show any aggression.
"It was striking. The female that cannibalised the body the most, she's the mother of the top two high-ranking males. Her sons were the only ones that really didn't attack the body aggressively," Pruetz told New Scientist, adding that Mamadou even tried to wake his old partner.
National Geographic explains that the attack might not be just because they did not want Foudouko back, but because of sex. Foudouko may have approached a female chimpanzee in heat. Competition for mates is fierce in Fongoli, where males outnumber females.
Meanwhile, since Foudouko's death, Mamadou has been kicked out of the group by the same young males who attacked Foudouko. The findings were last week in the International Journal of Primatology.