In the summer of 1995, primatologist John Mitani arrived at Uganda’s Kibale National Park, enveloped by an ancient rainforest with a canopy reaching 40 metres. Having previously worked in Tanzania’s Mahale Mountains, which housed the largest known chimpanzee population of about 100 individuals, Mitani was struck by the dense presence of apes in Kibale. He recalls that within just a few days of arriving, it was clear something unusual was occurring, noting that there were chimpanzees everywhere. Its canopy stretching to heights of 40 metres, the old-growth east African rainforest enveloped him. Fruit trees bowed under the weight of African star apples and bountiful Ficus mucuso figs. But there were rumours that this section of Kibale – only accessible via a 12-hour drive from the capital, Kampala – might host an even more unusual abundance of apes.
Mitani, a Northern California native and then a professor at the University of Michigan, eventually collaborated with colleagues to count nearly 200 chimpanzees inhabiting the Ngogo forests. This area had been established in the 1970s to study red colobus monkeys. In late 1995, Mitani and Yale primatologist David Watts co-founded the Ngogo Chimpanzee Project using a $500,000 grant from the US National Science Foundation. Over the next three decades, this initiative became one of the world’s twelve long-term research sites for chimpanzees in their natural habitat. Their raucous calls often deafening, furry black blobs darted through the jungle. Later that year, Mitani co-founded the Ngogo Chimpanzee Project with the Yale university primatologist David Watts, using a $500,000 (£380,000) award from the US National Science Foundation.
Building trust with the apes proved difficult, as the researchers spent years chasing them across varied terrain. The breakthrough occurred during Mitani’s second year when a 25-year-old male with a cleft palate, named Hare, allowed the researcher to follow him after descending from a fig tree. Mitani, now 72, later noted in the 2022 anthology Chimpanzee Memoirs that gaining Hare’s trust was a profoundly gratifying moment. Exciting and exhilarating, days were spent chasing them over hills and down valleys. “It was fun.
Over 85 months of fieldwork—totaling roughly seven years—Mitani and nearly 90 researchers transformed a small set of tents into a significant research station. Their early work stunned the scientific community by revealing that unrelated male chimps could form strong, cooperative alliances. Furthermore, their research indicated that hunting and consuming red colobus monkeys served a social bonding function beyond mere nutritional intake, and they observed some of the lowest mortality rates ever recorded for a wild chimp population. The chimps were not accustomed to human presence and were quick to run away whenever researchers approached.
The atmosphere shifted significantly in June 2015. Mitani observed a group exhibiting nervous behavior, scattering unexpectedly at the sound of others. This event marked the beginning of a prolonged, violent conflict between members of what had previously been a unified group. The struggle was later chronicled in the 2023 Netflix documentary series Chimp Empire and described in an April study in the journal Science as potentially the first instance of a civil war among wild chimpanzees.
By 2018, the Ngogo community had split into two distinct factions. During the ensuing conflict, nine males and 19 infants were killed. Despite this bloodshed, researchers discovered the unexpected demographic outcome that female fertility doubled and offspring survival rates increased significantly within the area. For Mitani, however, the experience was deeply distressing, as he had spent decades watching the once-cohesive troop thrive.
The emotional toll of documenting the violence was heavy. Mitani admits he was in denial for some time, struggling to reconcile the conflict with his long-held view of the group. He confessed that he delayed writing about these events for over a decade because he was reluctant to record such a dark chapter in their history. The process of returning to the site became increasingly difficult as the killings persisted.
Mitani cautions against using these findings to infer that humans possess an inherent evolutionary inclination toward such violence. He points out that this behavior has not been observed among bonobos, who share a common ancestor with humans and chimps dating back roughly 8 million years. He argues that some colleagues tend to overemphasize behavioral parallels, concluding that if he has learned anything, it is that chimpanzees are fundamentally different from humans.
Looking ahead, Mitani expresses concern regarding the future of his research, particularly following reports that funding may be eliminated under the Trump administration’s proposed 2027 budget. He remains hopeful that the ongoing study of these animals will continue to reveal important insights, ultimately inspiring humanity to ensure it can continue coexisting with them on the planet.
