The first example was observed in a group of tamarin monkeys in captivity in New York City's Central Park Zoo.
A group of cotton-top tamarins were being studied to learn more about their use of human-directed mobbing calls, but scientists saw that when a disliked member of zoo staff entered their habitation, the primates communicated with each other using "low amplitude vocalizations," the Independent reported.
The research concluded that the tamarins reduced their vocalization amplitude in the context of exposure to a potential threat.
The paper has been published in the journal of Zoo Biology.
--ANI (Posted on 26-09-2013)