Researchers noticed monkeys at New York's Central Park Zoo "whispering" to each other.
The scientists noticed the zoo's cotton-top tamarin (Saguinus oedipus) strange vocalizations when attempting to record the primate's alarm sound for a different story, i09 news reported.
The team believed the monkeys would sound the alarms when they were afraid of people, but instead the monkeys were quiet when a stranger walked into the room.
When the team played back the recording of the oddly silent tamarins, they noticed the primates were communicating in extremely hushed tones.
Rachel Morrison and Diana Reiss, the lead researchers of the study, believe the findings are "evidence of convergent evolution in communication strategies used by social and cooperative species," the Daily Mail reported.
Other animals have also developed the ability to whisper for various reasons. The barbastelle bat has learned to lower its voice in order to remain undetected by their insect prey, Global Animal reported.
"All of the other bats have a large call that travels far, [like] a bright torch," Holger Goerlitz, a biologist at the University of Bristol said, "But the barbastelle bats' sonar is like "a candle, only 'illuminating' the area just around them."
Not all moths have ears, so this ability gives the bats an advantage in catching eared snacks.
A past study asked the question: why don't apes have musical talent? Other animals such as birds and whales are capable of singing a tune, but apes are not as melodic, the Daily Mail reported.
Researchers at the Lung Clinic at Örebro University Hospital believe the ability to sing grows from the need to counteract disturbing outside sound when traveling in a group.
"In the middle of each stride we can hear our surroundings better. It becomes easier to hear a pursuer, and perhaps easier to conduct a conversation as well," researcher Matz Larsson said, the Daily Mail reported.
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