When a new leader was crowned, it was hoped that the community would settle down and peace would prevail. But two younger pretenders had other ideas, their lofty ambitions meaning they wanted to seize power for themselves. The resulting fracture in the group led to years of brutal warfare, during which raids were conducted, ambushes set, and no one was above murder.

The conflict became known as the Four-Year War of Gombe, and is the only known fully documented chimpanzee civil war. Now a new study has re-examined the episodes that led up to the war, to try to figure out what sparked it.

The events were recorded by Jane Goodall after a decade of watching the community of chimps at Gombe National Park, at a time when chimpanzees were still thought to be peaceful, forest-living apes. Between the years of 1974 and 1978, she observed the extreme violence that can pervade as the one community seemingly split and the apes waged a savage war. What she witnessed truly disturbed her.

Goodall showed that the chimps at Gombe were far more violent than thought. Ikiwaner/Wikimedia Commons

“Often when I woke in the night, horrific pictures sprang unbidden to my mind – Satan [one of the apes], cupping his hand below Sniff's chin to drink the blood that welled from a great wound on his face… Jomeo tearing a strip of skin from Dé's thigh; Figan, charging and hitting, again and again, the stricken, quivering body of Goliath, one of his childhood heroes,” Goodall wrote in her memoir of her time at Gombe.

But the cause of the war has always been up for debate. Was it a natural event that was occurring independently of Goodall, who was simply observing the apes, or was it sparked by the feeding station that she had set up in the forest, bringing an unnatural group of chimps together?