A new study led by researchers from the German Primate Center, a division of the Leibniz Institute for Primate Research focuses on how West African green monkeys can interpret unknown sounds and its significance for language evolution. Other studies showed that East African vervet monkeys use a specialized call which signals the presence of predators like the eagle, leopard or snake. These special alarm calls can be interpreted by fellow animals, which are then able to rush to safety before the threat arrives.
The team of researchers observed the West African green monkeys, which are closely related to the vervet monkeys. During an experiment, the researchers sent a drone in an area where a group of monkeys was present. At a later time, they played the sound of the drone and observed the reaction of the monkeys.
As expected, the monkeys were alerted by the foreign presence. However, instead of creating an alarm call, they decided to adopt a call borrowed from the East African vervet monkey. That particular call is used to signal the presence of aerial predators, including eagles.
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This discovery infers that the vocal call structure follows a rigid pattern established in the course of evolution. The East African vervet monkeys use three distinct calls to signal the presence of their arch enemies: snakes, leopards, and eagles. In the case of each enemy type, the call is accompanied by a specific protective action to counter that particular threat.
When the signal for leopard is heard monkeys in the immediate area will climb into a tree. If the presence of an eagle is signaled, they will look at the sky and hide. Last but not least is the dangerous presence of a snake, which prompts the monkeys to stand on two legs and remain motionless.
The researchers concluded that the alarms calls are heavily linked to the wider evolution of the vervet monkey. The study was published in a scientific journal.