By Ellyn Lapointe Published May 21, 2025 | Comments (0) | A young male white-faced capuchin carries a baby howler monkey on its back, captured by a remote camera trap on Jicarón Island © Brendan Barrett / Max Planck Institute of Animal Behavior A young male capuchin named Joker may just be the world’s first primate influencer. But the trend he started—abducting babies belonging to a separate species—has deadly consequences. Joker is one of many white-faced capuchins living on Jicarón Island off the coast of Panama. Researchers had been using cameras to observe the behavior of these round-headed, stocky monkeys when, in 2022, something unusual caught the eye of Zoë Goldsborough, a doctoral researcher at the Max Planck Institute and a research associate at the Smithsonian Tropical Research Institute in Panama.  She was scrolling through camera-trap footage when she spotted a male capuchin carrying a baby monkey on its back. This was already an unusual sight—female primates are almost always the ones to carry the young. But upon closer inspection, it got even stranger. “I really quickly saw that the coloration was completely wrong,” Goldsborough told Gizmodo. “The capuchin monkeys have dark fur and light face, and this [baby] had lighter fur and a dark face.” The only other primates on the island are howler monkeys, and this infant’s coloration matched that species, she explained. “So it was really quickly clear that it could only be a howler monkey, but that just made no sense whatsoever.” This sighting inspired Goldsborough to sift through tens of thousands of images captured by all cameras deployed around the same time period, according to a statement from the Max Planck Institute. She found four different instances of the same capuchin, a male who she named Joker, carrying baby howler monkeys. “With everything we found, we had more answers, but also more questions,” Goldsborough said.  At first, she and her colleagues thought this behavior could be a form of adoption—when an animal assumes a parental role for an infant of another species. It’s relatively common among primates, but almost exclusively carried out by females who presumably do it to practice caring for young, according to the Max Planck Institute. So what was motivating Joker—a male—to kidnap these baby howlers? Before Goldsborough and her colleagues could begin to answer that question, new ones arose. They discovered video and images of four more young male capuchins carrying baby howlers, five months after Joker started doing it. They were copying him—it was a real-world case of “monkey see, monkey do.” The researchers’ study, published Monday in the journal Current Biology, details how the trend-setting Joker and his four followers carried 11 different howler infants over the course of 15 months. The babies clung to their backs or bellies as the capuchins went about their business, sticking together for up to nine days at a time. Aside from some occasional annoyance when the infants tried and failed to nurse, Goldsborough said the capuchins were gentle with their strange passengers—Joker especially. “He seems to be really interested in having these infants and carrying them for long periods of time,” she said.  But because these males could not produce milk, the infants didn’t fare well with their adoptive fathers. The researchers saw four babies die from apparent malnourishment, and suspect the others perished as well. In three cases, the capuchins continued to carry their dead infant for at least a day after it had passed. Based on their findings, the researchers determined that this was a case of interspecies abduction, not adoption. It’s not yet clear why the capuchins picked up this trend, as it is rare for primates to kidnap the young of other species, but it’s not uncommon for one individual’s behavior to spread to other members of the population through social learning. As for why Joker initiated the behavior in the first place, Goldsborough says there are a few possible motivations. His remarkably gentle interactions with the howler babies suggest he may have had some sort of caring motivation, she explained. “I think it’s possible that there was something a little quirky about him, or that he was kind of lonely in a way,” she said.  To get to the root of his behavior, Goldsborough wants to learn more about his social position. Determining whether Joker is a leader or a loner could provide further insights into how social learning manifests in primate groups, she said. Daily Newsletter You May Also Like By Ed Cara Published May 15, 2025 By Isaac Schultz Published May 6, 2025 By Isaac Schultz Published May 5, 2025 By Ed Cara Published April 25, 2025 By George Dvorsky Published March 21, 2025 By Ed Cara Published February 28, 2025

A male white-faced capuchin monkey carrying a baby howler monkeyBrendan Barrett/Max Planck Institute of Animal Behavior Capuchin monkeys on a remote Panamanian island are abducting babies from howler monkey families, in a first-of-its-kind trend. The wild population of white-faced capuchins (Cebus capucinus imitator) living on Jicarón Island has been monitored with 86 motion cameras since 2017 to capture their sophisticated use of stone tools to crack open hard fruits, nuts and shellfish. Five years into recording the footage, in 2022, a researcher noticed one of the young male capuchin monkeys with an infant monkey from another species clinging to its back. This capuchin, nicknamed Joker, picked up at least four baby howler monkeys (Alouatta palliata coibensis) over four months, sometimes holding onto them for more than a week. Advertisement At first, the researchers thought it was a case of “one individual who maybe is a little weird or a little quirky”, says Zoë Goldsborough from the Max Planck Institute of Animal Behavior, who spotted the behaviour. “We didn’t expect to find this.” Then, five months after they saw Joker with an infant, four other young male capuchins were found carrying around howler babies. Over 15 months, the capuchin group took in 11 howler babies younger than four weeks old. The behaviour spread around the population through social learning, like a “primate fad or fashion”, says Andrew Whiten at the University of St Andrews, UK, who wasn’t involved in the study. Unmissable news about our planet delivered straight to your inbox every month. Sign up to newsletter While mature female monkeys sometimes adopt abandoned babies of other species, which may be a way to practise caring for their young, the Jicaròn monkeys doing this are all immature males. And instead of adopting abandoned infants, they seem to be actively taking the howlers from their families. There is no footage of the thefts, but they did document capuchins preventing the howler babies from escaping. Footage also shows howler monkey parents searching and calling for their infants in the canopy as the capuchins get defensive. The abducted infants probably all die from malnourishment, since they are too young to survive without their mother’s milk. Researchers saw at least three howler monkey infants being carried around even when dead. Two white-faced capuchins with a baby howler monkeyBrendan Barrett / Max Planck Institute of Animal Behavior Learning from others can be beneficial, which is why a trend can take off even when the behaviour has no real benefits to the monkeys, says Whiten. Since the Jicarón capuchins have no predators and very little competition, the craze could have arisen as a result of having spare time to try new things, and possibly out of boredom. There might also be something about the conditions of life on a remote island that are conducive to innovative behaviours arising and being spread. It is these same young male monkeys who most use tools on Jicarón, notes Goldsborough. “Maybe if you have a tradition already, you’re more likely to also copy their other behaviours.” Topics:

Young male capuchins have developed a strange trend of acquiring baby howler monkeys. It doesn't end well for the babies.

News Animals Juvenile capuchins are kidnapping infants of another monkey species Among primates, spending time with infants from another species is very rare Capuchins are highly intelligent primates with a penchant for quirky behavior. Their latest gaff? Kidnapping endangered infant howlers. Niki Harry/Getty Images By Freda Kreier 1 hour ago There’s a serious case of stranger danger unfolding on an island off the coast of Panama. A gang of five juvenile capuchin monkeys living on Jicarón Island has started abducting baby howler monkeys, researchers report May 19 in Current Biology. This bizarre fad, which has no clear purpose, is often deadly for abductees. Capuchins “do such interesting, weird, quirky and sometimes dark things,” says Brendan Barrett, an evolutionary behavioral ecologist at the Max Planck Institute of Animal Behavior in Konstanz, Germany. These behaviors “can offer a dark window of reflections into what we do.” Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday.

Capuchin Monkeys Caught on Camera ‘Abducting’ Baby Howler Monkeys in a Strange Tradition Seen for the First Time Scientists on Panama’s Jicarón Island were mystified by photos and videos of young male capuchins carrying howler monkeys on their backs for days at a time Lillian Ali - Staff Contributor May 19, 2025 11:00 a.m. A howler monkey infant, only a few days old, clings to a subadult white-faced capuchin monkey as it uses tools. Brendan Barrett / Max Planck Institute of Animal Behavior In June 2022, while watching footage from an island off the western Pacific coast of Panama, researchers spotted a strange wildlife behavior they’d never seen before. A young, male capuchin monkey walked past the camera with a baby howler monkey clinging to its back. “What am I looking at here?” Meg Crofoot, an ecologist at the Max Planck Institute of Animal Behavior and one of the researchers observing these capuchins, tells Smithsonian magazine about the first time she saw the footage. “It’s so weird.” As they played back more of the recorded videos, the scientists realized they were observing a new social tradition among young male capuchins: abducting baby howler monkeys. The kidnapped howlers were all less than four weeks old, and in some videos taken by the research team, adult howler monkeys can be seen or heard calling out for the missing babies. While the male capuchins did not directly hurt the babies, they could not provide milk to them, and several howlers died of malnourishment, the research team reports in a study published today in the journal Current Biology. Capuchin monkeys are abducting baby howlers. But why? Watch on The research started on Panama’s Jicarón Island in 2017, when scientists obtained enough funding to set up a project there. They placed camera traps, which took photos or videos when they detected motion, and discovered the island’s white-faced capuchin monkeys regularly use stone tools. That marked the first known population of tool-using capuchins. But after several years of monitoring the monkeys, Max Planck Institute of Animal Behavior researcher Zoë Goldsborough observed the new behavior from the group, spotting the first instance of a young male capuchin carrying around a baby howler monkey. “This has never been observed anywhere else, not on this island, or in any other populations of capuchin monkeys,” Goldsborough says in a statement from the Max Planck Institute of Animal Behavior, which, along with the Smithsonian Tropical Research Institute (STRI), funded the research. Because the researchers used motion-sensing cameras, they could easily jump back and forth in time to look for new sightings and retroactively check if they missed old ones. They traced the first instances of this behavior to one monkey, who they nicknamed “Joker,” initially seen carrying a howler infant in January 2022. But at the start, Joker’s antics didn’t seem to catch on. A howler infant carried on the back of Joker, the first capuchin to "innovate" the carrying tradition. A juvenile capuchin looks at them from the side. Brendan Barrett / Max Planck Institute of Animal Behavior Five months after the first sighting, however, researchers saw even more capuchins seemingly copying Joker and carrying howlers. Over 15 months of footage, they observed 11 infant howlers carried by young capuchins, each for up to nine days at a time. While Joker “paid more attention to the babies that he carries,” and was generally more interactive, the capuchins that later adopted the behaviors “really don’t interact with the babies,” says Crofoot, who, along with Goldsborough, is also a research associate at STRI.  Researchers do not know how the capuchins got the howlers in the first place. Howler monkeys primarily live in trees, so Crofoot assumes that is where the capuchins found them. Why capuchins appear to be abducting baby howlers is still unclear, but the team examined multiple possibilities. Since howlers and capuchins have different diets, the researchers ruled out competition for food. They also did not see the “carrier” capuchins getting positive social attention from their peers, though sometimes one capuchin would lose interest in the howler he was carrying and drop it for another capuchin to scoop up. The team’s suggestion? Boredom. Life on Jicarón Island has few competitors and no predators for the capuchin monkeys. This low-stress and potentially under-stimulating environment might lead the monkeys to create new behaviors, the researchers say. “Capuchins appear to carry howler infants solely for carrying’s sake,” they write in the paper. A white-faced capuchin monkey uses stone tools at a streambed while carrying a baby howler on its back. Brendan Barrett / Max Planck Institute of Animal Behavior Susan Perry, a primatologist at the University of California, Los Angeles, who has studied social behaviors among capuchins and was not affiliated with this research, suggests the carrying behavior stems from capuchin males wanting to alloparent other infants, or take care of babies that are not their own offspring. “Male capuchins frequently steal capuchin infants,” Perry writes in an email to Smithsonian magazine. “I think this is because they are trying to develop relationships with infants that are going to be their sidekicks/henchmen when they immigrate.” Georgia State University primatologist Sarah Brosnan, who was also unaffiliated with the research, compares the behavior to the use of a “toy,” especially because it was primarily observed among juvenile and immature capuchins. “These are juveniles,” Brosnan says. “I don’t think that they are grabbing [howlers] because they’re kidnapping, I think they’re grabbing it because it’s an interesting and engaging toy. It makes noise, it moves.” This isn’t the first time a hard-to-explain social tradition has been recorded in capuchin monkeys. More than 20 years ago, Perry observed capuchin groups demonstrating social behaviors, like “hand-sniffing,” when one capuchin sticks a finger up another’s nose for several minutes, and turn-taking “games,” such as when monkeys try to retrieve objects hidden in each other’s mouths. “It suggests that capuchins are really, really interested in these social traditions—really strongly socially motivated—and easily developed these social traditions,” Brosnan adds. To Crofoot, the findings show that humans are not alone in having “arbitrary” social traditions, born from boredom-fueled innovation. Just as humans tend to compare our species to other primates in positive terms, such as with tool use and intelligence, our primate relatives can share hard-to-explain social dynamics that might harm other species as well. “I think that’s a really interesting, important thing for understanding ourselves, even if it also has this kind of grim side to it,” Crofoot says. Get the latest stories in your inbox every weekday.