Tamarins in the Central Park Zoo Are the First Monkeys to Be Caught Whispering

A supervisor at the Central Park Zoo was experiencing something familiar—when he walked into a room, voices became hushed—but it wasn’t his coworkers who were quietly gossiping about him. It was a family of cotton-top tamarins, the first non-human primates who were observed to whisper.

Cotton-top tamarins are small monkeys with distinctive Beethoven or Einstein-like shocks of hair. Weighing about a pound, they're native to the jungles of Colombia, where they live in “highly cooperative” communities. They also are some of the animal kingdom's most interesting talkers. Even compared to other monkeys, cotton-top tamarins have a high degree of vocal control and variation: they chirp, whistle, squeal, and shriek. And, to their own surprise, researchers discovered that they whisper too.

Psychology researchers from City University of New York were trying to study the tamarin’s “mobbing” behavior, which they do in the wild in the presence of predators, and involves not only myriad growls and barks, but also lunging at the predator and flicking their tongues.

The zoo staff knew that a family of five tamarins had it in for a certain zoo supervisor, and they guessed it was due to his involvement in the tamarin’s capture and medical procedures. In the past, he had brought out a strong mobbing reaction, including loud vocalizations, from the group. The plan was to have the supervisor come in and watch how the monkeys reacted. Then once they lunged at the supervisor, as the researchers assumed they would, have him leave and study the response.

But in the observation phase, the monkeys didn’t mob the supervisor. Even as their hair stood up and they quickly withdrew, the monkeys didn't make loud noises. They weren't cowering or paralyzed with fear either. Upon closer examination the researchers realized that the monkeys were actually making low amplitude vocalizations. They were whispering.

The study, published in the journal Zoo Biology, notes that other species have been found to “whisper” to fellow members of the species in the presence of threats or during mating time. Richardson’s ground squirrels quietly alert each other about threats, while the barbastelle bat lowers its voice so it can get the jump on potential prey. Asian corn borer moths and croaking gourami fish use softer calls while mating, so as to avoid both predators and would-be rivals.

But the cotton-top tamarin is the first non-human primate to be caught whispering.  It’s possible that other primates have been doing the same, but thanks to their gift for it, we’ve never noticed. Naturally, researchers hope to look at other primates and see if there’s anything that they would like to share with everyone.