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In the verdant forests of Jicaron Island, near Panama, an extraordinary behavioral phenomenon among white-faced capuchin monkeys has captured the attention of primatologists from around the world. Young male capuchins have been observed systematically kidnapping baby howler monkeys, an unprecedented behavior in the animal kingdom documented by researchers in May 2025. This peculiar tradition involves the capuchins abducting infants from their mothers with no apparent predatory intent.

The initial discovery occurred in 2022 when behavioral ecologist Zoë Goldsborough, analyzing footage from motion-sensor cameras on the island, noticed a capuchin carrying a baby howler monkey. The capuchin, distinctive with a scarred mouth and nicknamed "Joker," was documented abducting four different howler infants. Initially thought to be an isolated case of cross-species adoption, this behavior soon spread among the capuchin population. Within fifteen months, five capuchins were seen carrying eleven baby howlers, while frantic adult howler monkeys were captured on camera searching for their missing young.

What baffles scientists is that the capuchins do not consume or play with the kidnapped infants. Instead, they carry them for several days, during which the infants often die from dehydration or starvation, unable to nurse. Unlike previously known instances where orphaned animals are taken under care by others, these abductions do not appear nurturing in any way.

The actual mechanics of these kidnappings remain elusive, primarily because the motion-sensor cameras are ground-based, while the primates dwell high in the canopy of Coiba National Park. Despite the considerable size difference, with adult howlers being three times larger than capuchins, the capuchins have mastered separating very young infants from their mothers without causing visible injuries.

By July 2023, researchers had documented another similar incident, although the frequency seemed to decline. This decrease might be attributed to the dwindling population of howler monkeys on the island, who are already classified as an endangered species, raising concerns for their conservation.

This behavior is believed to be a social tradition or fad among young male capuchins, akin to other observed arbitrary behaviors within animal populations. Previous studies have noted similar instances, such as capuchins in Costa Rica grooming porcupines, and marine mammals like orcas balancing dead salmon on their heads, showcasing how cultural practices can spontaneously evolve and spread among animal groups.

Initially studying Jicaron's capuchins for their notable tool-use abilities in 2017, researchers found these primates using stones to crack open nuts and shellfish—a testament to their intelligence. With an abundance of food and absence of predators, these capuchins have substantial leisure time, leading to an array of behaviors both practical and puzzling.

The detailed observations of this behavior were published in "Current Biology" in May 2025, with Zoë Goldsborough as lead author. This study marks the first documented instance of one species systematically kidnapping another's young, expanding scientific understanding of primate behavior and social learning.

These findings emphasize the remarkable behavioral adaptability of primates and contribute to the broader comprehension of animal cognition and social structures. Each newly documented behavior enhances our grasp of the complex and, at times, astonishing world of animal societies.