Capuchin monkeys kidnap babies of another species — and the deadly abductions are caught on camera

CBS News

19-05-2025

A baby howler monkey clung to the back of an older male monkey, its tiny fingers grasping fur. But they're not related and not even the same species.
Scientists spotted surprising evidence of what they describe as monkey kidnappings while reviewing video footage from a small island of Panama. The capuchin monkeys were seen carrying at least 11 howler babies between 2022 and 2023, researchers said Monday.
"This was very much a shocking finding," said Zoë Goldsborough, a behavioral ecologist at the Max Planck Institute of Animal Behavior in Germany. "We've not seen anything like this in the animal kingdom."
The monkeys' motivations remain under investigation. Capuchins are house cat-sized monkeys found in South America and Central America. They are long-lived, clever and learn new behaviors from each other. One group of capuchins in Panama has even learned to use stone tools to crack open nuts and seafood.
This photo provided by researchers shows a baby howler monkey clinging onto a young adult male capuchin monkey on Jicarón Island, Panama in September 2022.
Brendan Barrett/Max Planck Institute of Animal Behavior via AP
Goldsberg and other researchers at Max Planck and the Smithsonian Tropical Research Institute had set up more than 80 cameras to study capuchin tool use but were surprised to see the first howler babies appear in early 2022.
Goldsborough initially found four different howler infants being carried. In nearly all cases, the culprit was the same subadult male. The scientists nicknamed the capuchin Joker because the small scar at the side of its mouth reminded them of the "Batman" villain.
At first, the scientists thought this was the "heartwarming story of a weird capuchin adopting these infants", Goldsborough said.
Then the researchers started finding other cases not involving Joker. The scientists were puzzled because the capuchins did not eat or prey on the babies, nor did they seem to enjoy playing with them.
Goldsborough said they eventually realized these abductions were a social tradition or "fad" among the island's young male capuchins.
Grim fate for abducted babies
The footage showed the capuchins walking and pounding their stone tools with baby howlers on their backs. But cameras did not capture the moments of abduction, which scientists said likely happened up in the trees, where howlers spend most of their time.
"Our window into this story is constrained," said co-author Margaret Crofoot of Max Planck and the Smithsonian. The findings were published Monday in the journal Current Biology.
In most or all cases, the baby howlers died, researchers said. Infant howler monkeys would normally be carried by their mothers while still nursing. All the babies in the video — from a few weeks to a few months in age — were too young to be weaned.
"A hopeful part of me wants to believe some escaped and went back to their mothers, but we don't know," said Crofoot.
The videos recorded a few instances of young capuchin males still carrying howler babies that had died, likely from starvation. Many animals -- from gorillas to orcas -- have been observed carrying their dead offspring, though scientists aren't sure the reasons.
Why did the capuchin males do it? There were no signs of deliberate aggression toward the babies and they weren't eaten, ruling out predation.
"We've all spent hours wracking our brains -- why they would do this?" said Goldsborough.
The first baby-snatcher may have had a confused "caring motivation," or parental instinct, because he showed gentleness interacting with the infants, she said. Then four other males copied his actions.
The researchers said they don't believe the capuchins harmed the babies on purpose. So far, only one group of capuchins has been known to kidnap.
The research shows the "remarkable behavioral variation across social groups of the same species," said Catherine Crockford, a primatologist at the CNRS Institute for Cognitive Sciences in France, who was not involved in the study.
Cultural fads spreading among animals is rare but not unheard of.
Barrett has previously studied capuchins in Costa Rica that suddenly started grooming porcupines, before growing bored of the trend.
And back in the 1980s, killer whales took to donning dead salmon on their heads off the northwestern U.S. coast. This trend returned decades later when orcas were again spotted wearing these "salmon hats" last year.
Agence France-Presse contributed to this report.