One of the most remarkable aspects of life in the Amazon basin noticed by every visitor almost from the moment they first enter the rainforests of South America is the cacophony of bird and animal calls that fills the air by day and night.
Scientists now believe that at least one of the calls that fill the Amazon may be used for what they have termed “tactical deception”.
According to a study published in 2009 by the behavioral ecologist Brendan C. Wheeler (*), the tufted, or brown, capuchin (Cebus apella nigritus) uses alarm calls in what appears to be a deceptive manner in order to monopolize food sources. The brown capuchin monkey has an extensive range, and is found in South American forests from Colombia to northern Argentina, including Tambopata National Reserve. Capuchin monkeys have been studied extensively by a number of primatologists, both in the wild and in captivity, who have focused upon their remarkable tool-making abilities.
To test his theory, the American-born researcher, currently based at the UK’s University of Kent, set up an experiment in the Amazon habitat contained within Iguazú National Park, in Argentina.
He erected platforms in the forest canopy upon which he placed slices of banana, a highly valued food source among primates. As troops of brown capuchins ate together as a group, including individuals low down in the social hierarchy, he observed that low status individuals, which regularly experienced difficulty in accessing food, emitted loud alarm calls normally employed to warn the group of the presence of a common predator. However, while Wheeler was able to confirm that no such predators were present in the area, he also observed how when nearby monkeys dropped their food and fled, the individual which had sounded the alarm call would remain, calmly picking up and feeding upon its “prize”.
While Wheeler acknowledges that this practice of apparently “crying wolf” may not be intentional, he suspects that it may be a learned process. He believes that while subordinate individuals may have begun by emitting alarm calls as an outlet for the stress of being unable to access a food source monopolized by dominant individuals, once they realized that as other group members fled they would be left alone with their bounty, they learned to repeat the behavior.
Given the brown capuchin’s widely studied skills in tool making, including the use of stones to open nuts which it has left to dry for up to a week, the use of containers for holding water, and the employing of sticks to reach food, it certainly does not seem impossible that this highly social, cognitively complex primate may have developed the ability to deceive in pursuit of personal gain.