Researchers Puzzled by Bizarre Trend of Baby Monkey Kidnappings
Researchers Puzzled by Bizarre Trend of Baby Monkey Kidnappings
A perplexing and “viscerally disturbing” trend has emerged among a group of young male monkeys on a Panamanian island. These juvenile and adolescent white-faced capuchin monkeys have been observed kidnapping the infants of a different species, the howler monkey, seemingly for amusement.
This unsettling phenomenon, recently documented in the journal Current Biology, suggests that humans may not be the only intelligent species whose young engage in destructive and seemingly pointless activities.
“They’re just doing it for the sake of doing it, to reduce their boredom or have something to do to fill the time and space in their lives,” said Brendan Barrett, a researcher at the Max Planck Institute of Animal Behavior in Germany. He described capuchins as “chaos agents” that are highly innovative and exploratory, often engaging in “interesting, strange things.”
A Bizarre Island Trend
The capuchin monkeys exhibiting this behavior live on Jicarón island, part of Panama’s Coiba National Park. Researchers have been studying them since 2017, using wildlife cameras, because these island monkeys are a rare example of a species that uses stone tools to crack open tough foods like crabs and coconuts.
Zoë Goldsborough, a behavioral ecologist with the Max Planck Institute, first noticed the odd behavior while reviewing camera footage. To her surprise, she saw a capuchin carrying a howler monkey baby, a sight she had never heard of before. Further review of the footage revealed that this was not an isolated incident. The bizarre trend began in January 2022, with a particular young male the researchers nicknamed “Joker,” who appeared to be the “innovator” of the activity.
Over several months, cameras caught Joker carrying four different howler infants for up to nine days at a time. This was a tragic development for the babies, who, without their mothers’ milk, showed signs of deterioration. Several infants were later found dead.
After observing Joker, other young males in the group—four in total—began to mimic his actions. Over a six-month period, these other capuchins were seen carrying at least seven more howler infants for stretches of two to eight days.
Monkey See, Monkey Do
While animals sometimes adopt abandoned young, this does not appear to be the case here. Researchers noted that adult howlers would call out to the kidnapped babies, and in one instance, an adult howler was seen attempting to retrieve an infant only to be scared off by the capuchins.
The abductions were not caught on camera, but researchers believe the young capuchins likely face significant risks, as adult howlers can weigh nearly three times as much. The number of stolen babies suggests that the capuchins may be traveling a considerable distance to find them, a detail that researcher Goldsborough finds “completely bizarre.”
The researchers noted a key difference in behavior: while Joker seemed to treat the infants with affection, the other capuchins who copied him appeared indifferent, or even annoyed, by the babies they carried. The adult capuchins in the group showed little interest in the activity.
According to Goldsborough, the fact that the behavior spread so quickly highlights the monkeys’ strong drive to learn from their peers, even when the actions have no clear, immediate benefit. She likened it to their tool-use behavior, which also requires practice with little immediate reward.
This isn’t the first time an animal trend has been observed. Chimpanzees have been seen wearing blades of grass in their ears as a “fashion trend,” and orcas have been spotted wearing dead salmon on their heads. However, capturing the entire rise and spread of a new trend solely with remote cameras is a significant achievement.
The researchers now hope their cameras will capture the end of this cruel hobby, as the abductions are likely devastating the local howler monkey population, which reproduces infrequently. The scientists believe that the island’s safe, resource-rich environment may be what gives the capuchins the freedom to engage in such random and risky innovations.
“We know that in humans, boredom is incredibly conducive to creativity and innovation,” Goldsborough said. For these island capuchins, stealing howler monkey babies may be “something to do to pass the time” in a safe environment, where they can experiment with new behaviors.
Christopher Krupenye, a primate cognition expert at Johns Hopkins University who was not involved in the study, noted that capuchins are “notoriously cultural,” with a wide range of social traditions, from tool use to odd behaviors like putting a groupmate’s fingers in their own eyes. He believes the camera footage is a valuable asset to the research but stressed that more direct observation is needed to fully understand how these kidnappings occur and spread.