India, April 11 -- For two decades, researchers observed members of the Ngogo chimpanzee group of Kibale National Park in Uganda spend their days eating fruits and leaves, resting, travelling and grooming in their tropical rainforest abode. But this stable community then fractured and descended into years of deadly violence. The researchers are now describing the first clearly documented example of a group of wild chimpanzees splitting into two factions, with one launching a series of coordinated attacks against the other. Adult males and infants were targeted, with 28 deaths. The researchers began studying the Ngogo chimpanzees in 1995. This was the largest-known group of wild chimpanzees, peaking at around 200 members. "So why split? Perhaps they became a victim of their own success when the group grew to an intolerably large size," said primatologist and study senior author John Mitani.P11...