Monkey See, Monkey Snatch? Capuchin “Kidnapping” Fad Baffles Scientists – And Raises an Unsettling Question

Deep on a secluded island in Panama, a bizarre and frankly “viscerally disturbing” new trend has taken root among a group of young male white-faced capuchin monkeys. Scientists, initially there to study the monkeys’ clever use of stone tools, have stumbled upon a perplexing behavior: these capuchins have started “kidnapping” baby howler monkeys, carrying the infants of an entirely different species around on their backs. The findings, recently published in the journal Current Biology, have left researchers from institutions like the Max Planck Institute of Animal Behavior and the Smithsonian Tropical Research Institute scratching their heads and pondering some rather uncomfortable questions about animal behavior and its potential mirrors to our own.

The “kidnapping spree,” as observed through wildlife cameras between 2022 and 2023, wasn’t an isolated incident. Researchers documented at least 11 instances where young male capuchins, often led by an apparent “innovator” nicknamed “Joker,” were seen with tiny howler monkey infants clinging to them. This wasn’t a gentle adoption story. The howler babies, far too young to be weaned and receiving no nourishment from their capuchin carriers, invariably deteriorated. “They’re likely probably dying from dehydration or lack of nutrition,” said Brendan Barrett, a researcher with the Max Planck Institute, noting that several were actually seen dead on camera. Crucially, the capuchins weren’t eating the babies, ruling out predation, and researchers say they “don’t believe the capuchins harmed the babies on purpose.” Adult howler monkeys were even heard calling for their infants, and, in one instance, a howler parent attempting a rescue was scared off by the capuchins.

So, why this strange and ultimately fatal fad? “We’ve all spent hours racking our brains why they would do this,” admitted Zoë Goldsborough, a behavioral ecologist with Max Planck. The current scientific hypotheses are varied. Perhaps “Joker,” the first to exhibit the behavior, had a “confused caring motivation” or a misdirected parental instinct. Given that capuchins are highly intelligent, long-lived, and known for social learning (they even teach each other tool use on this very island), it’s plausible that other young males copied this novel, if perplexing, activity. Brendan Barrett also suggested it could be a case of “just for kicks,” a way to reduce boredom. He describes capuchins as “chaos agents” that roam their environment ripping up and manipulating everything in sight, especially on Jicarón island, which is a relatively “easy living” environment with abundant food and no large natural predators.

The behavior is baffling because there’s no clear evolutionary benefit to the capuchins; in fact, abducting a howler baby likely carries significant risk, as adult howlers are much larger. And if the howler babies were to somehow survive to adulthood with their captors, they would eventually outsize them, making the long-term “logic” even more obscure.

This leads to some deeper, perhaps more uncomfortable, considerations. Could it be that researchers, when faced with such disturbing actions in intelligent primates, sometimes lean towards “milder” explanations? After all, capuchins elsewhere are anecdotally known for their mischievous, sometimes thieving, ways with human belongings like purses and food. Presenting this island group’s more tragic “fad” as simple boredom or confused instinct might avoid painting the animals in a light that could cause public alarm or misrepresent their general nature. Does this cause us to wonder, however speculatively, if there could be more complex, even strategic, interspecies dynamics or cognitive drivers at play that we simply don’t grasp yet, or are hesitant to articulate? While current science doesn’t support darker interpretations for this specific behavior, the sheer oddity of it certainly makes one ponder.

Brendan Barrett himself noted that seeing this kind of seemingly pointless activity, which is destructive to another species, occur in capuchins is “somewhat terrifying because it kind of reflects a mirror on the actions that we do as people.”

And that, perhaps, is the most unsettling takeaway. This baffling, unprecedented behavior, with no clear advantage for the perpetrators and fatal consequences for the victims, leaves us with a lingering question. In a world where human influence, even indirectly, reaches the most remote corners, and where our own species is no stranger to perplexing or destructive fads, one can’t help but ask about these intelligent, observant primates: Where does such a new and disturbing ‘hobby’ truly originate? Are they, somehow, picking up our bad habits?