Civil warfare within the chimpanzee paradise: “They have decimated the rival group” | Science | EUROtoday

On June 24, 2015, one thing modified in Kibali National Park (Uganda), house of the Ngogo, the most important chimpanzee group in Africa. “It was when we saw the first case of individuals from different neighborhoods of the group treating each other as strangers,” says Aaron Sandel, a primatologist on the University of Texas in Austin (United States) and first creator of a examine printed in Science which exhibits how from inside a gaggle that has spent years of peaceable coexistence, polarization can come up first, then division and, lastly, violence and warfare. Since that summer time, the Ngogo group has been break up in two and the deadly assaults, together with on the infants, have left dozens useless.

“I was with the chimpanzees from the western neighborhood. We were in the center of the territory when they heard other chimpanzees nearby. They must have been from the central neighborhood. Instead of approaching and gathering, as is typical among chimpanzees, they remained silent and visibly nervous: they made faces and touched each other to calm themselves. They acted as if they heard chimpanzees from another group, as if they were strangers. When the chimpanzees from the central neighborhood They approached, the western chimpanzees fled and the central chimpanzees chased them. The chimpanzees from both neighborhoods avoided each other for six weeks, something like this had never happened before,” says Sandel.

Among chimpanzees, and more so in large communities, it is common for subgroups to form. And Ngogo’s is the largest, reaching up to 200 individuals. But the relationships between the members of these groups of the same community are very fluid: a specimen can stay in one one year and go to another the next, they usually get together when they go to guard the borders, the babies that are born belong to the entire community and the encounters tend to be affectionate. But since 2015, paradise has been cracking.

The Ngogo community lives almost in a sanctuary. They occupy the central area of ​​the Kibali national park. There are no human settlements on the edges of the park. And the last leopard disappeared decades ago, so they have no natural predators. Observed intermittently since the seventies of the last century, it was in 1995 when scientists settled in the area to study them in a project that has continued since then and that has borne many fruits. Their territory is rich in food, something that has allowed the demographic expansion of the group. At the beginning of the century, there were already more than 100. More recently, thanks to their wars with neighboring communities, they expanded their territory and, with victory, their reproductive success.

After what happened in June 2015, researchers continued tracking the two groups, which they called central and western. The first kept the majority of the troops, 30 adult males and 39 adult females, compared to the thirty adults of the Westerners. They observed that the interactions were becoming fewer and fewer; in fact, they avoided each other when members of both groups went out on patrol. The authors of the study used indicators such as the number of moments in which the member of a group interacted with another through caressing, cuddling or delousing, so common before. They saw that this network of intimate contacts was losing its centrality, leaning towards the edges.

The segregation process coincided with the replacement of the alpha males of each group. The last link between the two occurred in 2018, when the last calf was born as a result of the union of a Western male with a Central female. Everything indicated that the social structure of the community had broken down. Then only disaster.

“In January 2018, three males from the western group grabbed this 15-year-old boy and ended his life with blows and bites. All three had small items of Erroll’s flesh. [el nombre del ejemplar] within the mouth when he was mendacity inert among the many leaves,” this newspaper wrote about the first lethal attack by Westerners against the centrals. Since then, six other adults have been murdered. And in 2021, the violence escalated with the first murder of a baby. 14 children have already died. Researchers have found another 14 individuals, between young and old, who died of unnatural causes. Although they were not witnesses, they fear that they also died violently. It so happens that all murdered belonged to the central group, which was triple the number of the western one.

Anthropologist Brian Wood, from the University of California, Los Angeles, published a work on the Ngogo community a few months ago before breaking up. In it he showed how the females of the group increased their fertility rate after annihilating a neighboring community and taking over their territory. For Wood, everything has to do with resources and competition with the other, even if the other was yours until he did nothing.

“Once the break up occurred, from the attitude of the western group, the central chimpanzees grew to become their most essential rivals. They had been the neighbors who took away the meals they needed,” says Wood, who has not been involved in the new work, in an email. And he relies on Darwinian theory to explain its violence: “Darwinian fitness is not limited to counting how many offspring are produced throughout life, but is a relative measure; a comparison between the number of one’s own offspring and those of competitors,” he says. This means that fitness can be increased by increasing one’s own survival, but also by decreasing that of competitors. “And that is precisely what Western chimpanzees have done: they have decimated the core group, significantly reducing their survival,” he adds.

In fact, Wood provides information presented at a recent conference. “The central chimpanzees, after facing attack by Western chimpanzees, now have the lowest survival rate ever documented in a community of wild chimpanzees,” he highlights.

The authors are reluctant to name what is occurring a civil warfare, one thing that the primatologist on the University of St. Andrews (United Kingdom), Josep Call, who is just not concerned within the analysis, agrees with. “The lethal phase is happening when there are already two groups,” he remembers. And he compares it to the battle that existed (and continues to rage) between Pakistan and India, which collectively grew to become impartial from the British metropolis. For him, the hot button is how some people “with whom you have lived all your life, now you treat them as strangers, are now the other.”