These adolescents and juveniles have started to kidnap the infants of another monkey species, seemingly just for kicks.
That’s what scientists think after watching a bunch of male white-faced capuchin monkeys walking around with baby howler monkeys clinging to their backs.
Island innovators The capuchins that have started kidnapping howler monkey babies live on Jicarón island, which is part of Panama’s Coiba National Park.
These capuchins had gotten ahold of at least seven different howler monkey babies, and carried them for stretches of two to eight days.
Plus, researchers could hear adult howler monkeys calling back and forth with the infants, who would sometimes try to crawl away.
A trend that one researcher described as “viscerally disturbing” has recently gained popularity among a group of young male monkeys on an island in Panama.
As if for fun, these young and adolescent monkeys have begun to abduct the young of other monkey species.
After witnessing several male white-faced capuchin monkeys moving around with young howler monkeys clinging to their backs, scientists have come to that conclusion.
The confusing baby-snatchings, which were documented in the journal Current Biology, imply that intelligent species other than humans have offspring that engage in seemingly meaningless pursuits that can harm other living things.
“They’re merely doing it to pass the time and have something to occupy their lives, and to lessen their boredom. And I think it’s a little scary to see this happen in another species because it kind of mirrors what we do as humans,” says Brendan Barrett, a member of the research team and an animal culture specialist at the Max Planck Institute of Animal Behavior in Germany. Barrett is also a research associate at the Smithsonian Tropical Research Institute.
In many ways, he says, capuchin monkeys are like humans and chimps. He calls them “chaos agents” that roam the forest, tearing up and modifying everything they see.
He asserts, “They’re very inventive and exploratory.”. They do strange and fascinating things. “.”.
inventors on the island.
Howler monkey babies are being abducted by Capuchins from Jicarón Island, which is located in Panama’s Coiba National Park. These island monkeys, in contrast to mainland Capuchins, have learned to crack open hard foods like seeds, crabs, and coconuts using stone tools. For this reason, scientists have been using wildlife cameras to observe them there since 2017.
Zoë Goldsborough, a research associate at the Smithsonian and behavioral ecologist at the Max Planck Institute of Animal Behavior, was shocked to see a capuchin carrying a howler monkey baby while she was analyzing video footage.
We had never seen anything like it before. “I hadn’t heard of it happening,” Goldsborough says. “I think for a brief moment I questioned whether it was just a strange-looking Capuchin monkey. However, it became immediately apparent that it was a different species. “.”.
She began to watch more of the video out of curiosity. And it became clear that this was not an isolated incident. It occurred repeatedly beginning in January 2022, when the researchers believe that a certain immature male known as “Joker” was the “innovator” of this novel activity.
“A small scar on the Joker’s face makes him recognizable,” Goldsborough says. Additionally, over the course of several months, the cameras captured him holding onto four separate babies for up to nine days at a time.
As a result of their lack of nutrition, the baby howlers suffered a terrible fate and gradually declined.
According to Barrett, who points out that these infants require their mother’s milk and that several were actually captured on camera dead, “they’re probably dying from dehydration or lack of nutrition.”.
But after witnessing Joker’s unique behavior, other young male Capuchins chose to emulate it.
The researchers observed four other immature males—two subadults and two juveniles—carrying around howler infants beginning in September and continuing for six months. These capuchins had taken in and carried for periods of two to eight days at least seven different howler monkey babies.
One monkey sees, one does.
Animals occasionally take in the young of other species that have been lost or abandoned, but this doesn’t appear to be the case in this instance, partly due to the large number of babies.
Moreover, the infants, who occasionally attempted to crawl away, could be heard calling back and forth with the adult howler monkeys. On one occasion, an adult howler attempted to retrieve a baby, but Capuchins scared it away, according to camera footage.
Camera footage did not document the actual abductions because they most likely took place in the trees. However, the researchers point out that adult howlers weigh almost three times as much as young capuchins, so a potential kidnapper could be in grave danger.
Since only a few small groups of howler monkeys live nearby, Goldsborough says, “I personally really want to know how they’re getting them, but mostly also how much effort are they putting into that?” The number of stolen babies raises the possibility that these capuchins may be traveling a considerable distance to find them. And that they would go to such lengths to go get these babies would be absolutely strange to me. “.”.
The other capuchins who imitated Joker appeared to be mainly unconcerned with the infants they carried, and occasionally even irritated, in contrast to his apparent loving and caring attitude toward the babies.
And the group’s adult Capuchins appeared blasé.
“Social interest isn’t very strong. They’re not behaving like they would if I were carrying a baby lion on my shoulders, Barrett explains.
The fact that Joker’s behavior was imitated by his peers, according to Goldsborough, shows how strong these monkeys are motivated to learn from others, even when the behavior doesn’t make perfect sense or have a clear, immediate advantage.
“There’s a period of time, especially when you’re young, that you are just copying this behavior with very little payoff,” she says, referring to the stone tool use of these monkeys, which requires some time to master. “..”.
On camera.
In the past, animals have been seen to participate in seemingly pointless activities that appear to spread among their groups.
For instance, chimpanzees have been observed sporting grass blades in their ears, seemingly as a fashion accessory. Furthermore, dead salmon have been observed worn by orcas on their heads in the shape of hats.
However, it is uncommon to use only remote camera footage to document the emergence and growth of a new trend. Barrett explains, “So that was kind of an exciting thing,” discovering a new method for researching animal culture. “..”.
He hopes that their cameras will document the disappearance of this pastime for the benefit of the howler monkeys.
Given that howler monkeys only have one baby at a time and don’t breed frequently, the local population must be severely impacted by the baby snatchings.
Whether the howler monkeys will begin to adapt their behavior to this frightening and unexpected new threat on an island that has long been a sort of safe haven, with no large predators and plenty of food, is one of the things the researchers are currently trying to figure out.
The researchers speculate that because of the island’s easy lifestyle, the Capuchins may have more time and freedom to engage in sporadic activities that result in activities like tool use or kidnappings.
In humans, “we know that boredom is incredibly conducive to creativity and innovation,” Goldsborough says. “.”.
Grabbing howler monkey babies might just become “something to do to pass the time” for these island capuchins, Barrett says, “in a kind of a boring environment where it’s relatively safe to come up with these potentially controversial innovations.”. “.
Not on this research team, Christopher Krupenye, a Johns Hopkins University primate cognition expert, claims to have witnessed other captive primates catching and tinkering with non-food items.
Krupenye says, “The innovator may have been motivated by interest and curiosity in this instance.”. Furthermore, considering how social and cultural Capuchins are, it’s possible that other onlookers have begun imitating their actions. “.”.
Though he considers the camera trap footage to be a “huge asset to this research program,” more in-person observations of the capuchins and their interactions with howlers would be beneficial in order to gain a better understanding of how these infant captures take place and how they spread.
“Notoriously cultural species, showing all kinds of adaptive cultural traditions, like using tools to obtain food, but also many arbitrary ones,” he says of the Capuchins. In one community, it was customary for people to stick a groupmate’s fingers in their own eyes. “.”.
