Monkeys Whisper, Too: Humans Aren't the Only Primates Who Lower Voices

Humans aren't the only primates that whisper to keep from being overheard. It turns out that tamarin monkeys do the same thing. Scientists have discovered these animals lower their voices to keep others from hearing what they're saying.

Whispering in the animal kingdom is nothing new. Gophers sometimes whisper and bats employ the behavior to avoid detection by moth prey, according to National Geographic. Yet none of these animals use whispering in the same way that humans do--in order to avoid being overheard by an unwelcome listener or predator. The cotton-tailed tamarin monkey, though, is another matter entirely.

Researchers first noticed these primates whispering in New York's Central Park Zoo. They were hoping to learn a little bit more about the kinds of calls that these creatures make to one another under different circumstances. Previous research had indicated that these monkeys are capable of making a wide range of noises, according to Phys.org.

During the course of their experiment, the researchers hoped to record the alarm call of these monkeys. When a distrusted zoo worker walked in, though, the tamarins didn't make any loud calls. Instead, the monkeys seemed to fall silent, according to io9. It was only later when scientists listened to the recordings made at the time that they realized the primates weren't actually silent. Instead, they had lowered their voices to "whisper" to one another.

The behavior is what is known as "low amplitude signaling," which, in the case of the monkeys, meant very soft chirps. While it's impossible to know what these monkeys were "saying" to one another, the researchers do have some theories. Most likely, the monkeys were reminding each other of the threat the man posed and were doing it in a way that wouldn't alert him, according to Phys.org.

The findings are important for better understanding the behavior of these monkeys. In addition, it reveals that even non-human primates can whisper to one another to keep from being overheard. It's likely that this behavior occurs in other species as well--we just haven't heard them yet.

The findings are published in the journal Zoo Biology.