Civil War Among Chimpanzees

Carl Zimmer, These Chimps Began the Bloodiest ‘War’ on Record. No One Knows Why. NYTimes, Apr. 9, 2026.

Near the end:

And the researchers are still trying to figure out what set off the conflict in the first place. “All of a sudden, yesterday’s friend becomes today’s foe,” said Dr. Mitani.

Within any group of chimpanzees, violence will flare from time to time — when apes converge on a tree full of fruit, for example, or when lower-ranked males vie to replace an old alpha male.

But this aggression can be dampened by the friendships that form over years. Some chimpanzees are especially social, jumping between many cliques. “They’re these important social bridges,” Dr. Sandel said.

In 2014, five adult males died, perhaps because of disease. Dr. Sandel speculated that these deaths ripped away some of the bridges that previously held the Ngogo groups together. Low-level conflicts blew up into something akin to civil war.

The Ngogo conflict could offer a glimpse at the kind of violence that might have flared up in our ancient forebears, given that chimpanzees and humans descend from common ancestors that lived about six million years ago.

“These findings tell us indeed that these civil-war-like types of conflicts were possible in the course of human evolution,” said Sylvain Lemoine, a primatologist at the University of Cambridge who was not involved in the study.

The Ngogo chimpanzees show how our ancestors could have gotten dragged into years of lethal fighting without ideology or cultural identity — let alone the language to talk about them.

Instead, shifting social bonds might have been enough to light the fire.

There's more at the link.

One study shows that male bonobos engage in violence more often, though less intensely, than male chimpanzees

Phie Jacobs, Bonobos, the ‘hippie chimps,’ might not be so mellow after all, Science, April, 12, 2024.

Chimps (Pan troglodytes) and bonobos (Pan paniscus) are the closest surviving relatives of modern humans. That makes them interesting subjects for scientists studying how aggression evolved in our own species. But the two apes are very different in their behavior. Chimps are patriarchal, forming all-male coalitions that patrol their territory; they react violently when they happen upon an outsider or neighboring clan. “Chimpanzee intergroup encounters are not possible,” Mouginot explains. “They will kill each other.”

Bonobos—which some have called “hippie chimps”—are far more peaceful, says Brian Hare, an evolutionary anthropologist at Duke who wasn’t involved in the new research. Their societies are dominated by females, and amicable interactions between communities are commonplace—and frequently marked by displays of enthusiastic sexual activity. And although bonobos are no strangers to conflict, scientists who study the apes have never witnessed a lethal encounter. As far as we know, Hare says, “no bonobo has ever murdered another bonobo.” [...]

Field researchers tracked 12 male bonobos from three communities—from the moment they woke until they settled down for the night—at the Kokolopori reserve, located deep within the Democratic Republic of the Congo. They did the same with 14 male chimps from two communities at Gombe Stream National Park in Tanzania. Every time an ape attacked or charged an adversary, or was on the receiving end of such aggression, a researcher was there to document it.

The results, Mouginot says, “really came as a surprise.” Overall, male bonobos turned out to be about three times as likely as chimps to engage in aggressive behavior. Although none of the encounters were lethal—and the team didn’t track the severity of injuries—bonobos weren’t afraid to push, hit, and bite their foes. Their aggression didn’t appear to be a turn-off for female bonobos, who actually preferred to mate with aggressive males. [...]

But whereas male chimpanzees frequently ganged up to or defeat rivals or bully females, bonobo males mainly participated in one-on-one fights and rarely attacked members of the opposite sex. In fact, males were far more likely to be on the receiving end of violence from groups of aggressive, dominant females.

There's much more at the link.

H/t Tyler Cowen. 

More –

• about the bonobos in the NYTimes. 
• The original research: Differences in expression of male aggression between wild bonobos and chimpanzees.

Handshakes in chimpanzee culture

Chimp Groups Have Their Own Distinct “Handshakes” https://t.co/LhNth6KQiY

— Bill Benzon, aka The Danish Space Laser (@bbenzon) June 22, 2021

From the article linked in the Tweet:

Over a 12-year span, two groups of chimpanzees maintained distinct, consistent styles of clasping hands while grooming one another, according to a study published May 26 in Biology Letters. The study findings represent a step forward in understanding chimp sociality and chimp culture—the behavioral patterns that are learned from others in a social group.

“The fact that different groups of chimps have different repertoires of gestures is something we’ve known for some time,” says Mary Lee Jensvold, the associate director of the chimp sanctuary Fauna Foundation, who was not involved in the research, but it was not clear how stable these behaviors were. “The longevity of [this study] is new,” she adds, noting that the semi-wild setting of the Chimfunshi Wildlife Orphanage Trust in Zambia where the research was conducted means that the study’s findings likely apply to wild chimps, too.

Chimp researcher William McGrew, then affiliated with the University of St. Andrews in Scotland, first reported observing handclasp grooming in wild chimps in 1978, and this behavior among chimp dyads has attracted increasing research interest in recent years. While the function of handclasping is not known, University of Antwerp researcher Edwin van Leeuwen, the study’s author, says he’s not bothered by the ease of comparing these handclasps to human handshakes, themselves a cultural behavior.

“We now have a lot of evidence of cultural differences across wild chimpanzee study sites, but much of that is about tool use and foraging behavior, so this evidence concerning a social custom is particularly valuable,” Andrew Whiten of the University of St. Andrews, writes in an email to The Scientist. He was not involved in this latest work but collaborates with van Leeuwen.

Handclasping behavior is unique among cultural characteristics of chimp groups in the sense that it does not appear to directly promote chimp survival. “To the best of my knowledge, this handclasp grooming is the only convincing evidence of social conventions in chimpanzees,” Susan Perry, an evolutionary anthropologist and field primatologist at the University of California, Los Angeles, who was also not involved in the work, writes in an email to The Scientist.

There's more at the link.

Apes with 'language' skills, Koko has died

"Koko — the gorilla known for her extraordinary mastery of sign language, and as the primary ambassador for her endangered species — passed away yesterday morning in her sleep at the age of 46. "https://t.co/QgGKaz9kyi

— Marc Kissel (@MarcKissel) June 21, 2018

Here's a post where I talk about other linguistic apes, Taboo, abstraction, and living with animals.

Koko had pet cats.

Koko wanted a birthday party celebration with her family, which included her cats! pic.twitter.com/r4XFa2gcNy

— Gorilla Foundation (@kokotweets) July 8, 2016

More Chimpanzee Grief

Pansy dies:

When the scientists at the park realized Pansy’s death was imminent, they turned on video cameras, capturing intimate moments during her last hours as Blossom [a close friend], Rosie [oldest daughter] and Blossom’s son, Chippy, groomed her and comforted her as she got weaker. After she passed, the chimps examined the body, inspecting Pansy’s mouth, pulling her arm and leaning their faces close to hers. Blossom sat by Pansy’s body through the night. And when she finally moved away to sleep in a different part of the enclosure, she did so fitfully, waking and repositioning herself dozens more times than was normal. For five days after Pansy’s death, none of the other chimps would sleep on the platform where she died.

Lippo dies:

[Brian Hare] was at a bonobo orphanage in the Democratic Republic of Congo when Lipopo, a newcomer to the orphanage, died unexpectedly from pneumonia. Although the other bonobos could have moved away from his body and traveled anywhere in their very large, heavily forested enclosure, they chose to stay and groom Lipopo’s corpse. When their caretakers arrived to remove the body, the vigil morphed into a tense standoff.

In the video Hare took, Mimi, the group’s alpha female, stands guard over Lipopo’s body. When the caretakers try to push the corpse out of the enclosure with long poles, Mimi fights them, viciously. She grabs the poles with both hands, wrenching them away from Lipopo. She calls to other bonobos, who help her fend off the humans from two sides. Even when the vet arrives with a tranquilizer gun, Mimi stands her ground, her mouth open wide in a scream that’s inaudible in the silent film. Mimi wasn’t related to Lipopo. In fact, she barely knew him, Hare told me.

From the NYTimes HERE.

Our Relatives the Chimps and Bonobos

Here's an interesting NPR interview with Franz de Waal in which he talks about chimpanzees and bonobos. It's relatively brief (12 and a half minutes). If you know relatively little about ape behavior, it's well worth your time.

The dimensions of chimpzanzee personality

Reported in Science Daily:

June 3, 2013 — While psychologists have long debated the core personality dimensions that define humanity, primate researchers have been working to uncover the defining personality traits for humankind's closest living relative, the chimpanzee. New research, published in the June 3 issue of American Journal of Primatology provides strong support for the universal existence of five personality dimensions in chimpanzees: reactivity/undependability, dominance, openness, extraversion and agreeableness with a possible sixth factor, methodical, needing further investigation.

Shazam!! Dog adopts chimp and my blog gets lots of visitors

I woke up this morning to discover that an old post, Two Puzzles Concerning the Self, have catapulted from nowhere to being the 10th most popular post on the site. How'd THAT happen?

The obvious hypothesis is that someone put up a link somewhere and that link was feeding the site. Sure enough I found a link from a Reddit discussion about a dog that had adoped a baby chimp. The discussion turned to "things chimps do" and that lead to this remark linking to my post. Lots of discussion about chimps in there.

But it was a dog that did the adopting. What about dogs?

Here's the photographs that sparked the discussion. I bet it isn't the dog that put the diaper on the chimp.

What's (a) Google wave?

1. A secret gesture Google employees use to identify one another when they’re on a spy mission in, say, China.

2. A unisex hairstyle available free of charge to Google employees in on-site styling salons.

3. Modeled on ‘the wave’ at sporting events, it’s gesture of solidarity among thousands upon thousands of people in a public place, such as Times Square in New York City, Piazza San Marco in Venice, or Tiananmen Square in Beijing.

4. Like microwaves, except very much higher in frequency. Used to carry the net traffic of ‘preferred’ users. Or perhaps it’s used in weapons designed to vaporize communications satellites.

5. A super tsunami created when an asteroid plunges into the ocean.

6. A special weave in the fabric of the jerseys required of all ‘inner circle’ Google employees.

7. The pattern of revisions to history books as a consequence of changes in the page-rank algorithm.

8. Earth tremors resulting from the explosion of a Goggle data center as a consequence of a massive viral attack.

9. The gesture Sergy and Larry make to the remaining inhabitants of earth when they set course for Mars in their solar sailer.

Chimpanzees Grieve

I’m not surprised. Both the BBC and Discover Magazine are reporting accounts of how chimpanzees deal with deaths of the old (Blair Drummond Safari and Adventure Park in Stirlingshire, Scotland) and the young (Bossou, Guinea).

I am, of course, glad that this behavior is being documented. But I’m a bit dismayed that it is being reported as news. Of course, chimpanzees grieve. They’re only human, no? Well, I suppose that’s the problem. We mustn’t anthropomorphize. And so we have to study and verify.

Still, I have this vague memory of having read that not so long ago doctors believed that neonates had no sense of pain. And so surgeons didn’t use anesthesia when operating on them. Did the little ones not scream?