Noisy monkeys keep their predators at bay.
Monkeys are highly vocal animals, so when they perceive a threat, they will often alert other nearby monkeys to the potential danger by emitting alarm calls.
These alarm calls are surprisingly specific, and other monkeys pay close attention. In 1980, researchers played recordings of different types of alarm calls to vervet monkeys to test out their responses.
When a “leopard” alarm call was played, monkeys on the ground climbed to the safety of the treetops. When they heard an “eagle” alarm call, they scrambled out of the canopy and hid on the ground below. When a “snake” alarm call was played, monkeys on the ground stood up straight and carefully scanned the ground.
It was clear that those monkeys could decipher the meaning behind each distinct alarm call.
A new study published in the journal Behaviour suggests that predators listen to the alarm calls too. With more than a year’s worth of sound, camera, and GPS data gathered from the sleeping site of a troop of vervet monkeys in Kenya and the leopards that frequent the surrounding areas, researchers found that when the monkeys detected an approaching leopard and let out an alarm call, the leopard would quickly retreat.
The leopards appeared to be taking their cues from the monkeys, deterred by their alarm calls. Though a leopard could overpower a noisy monkey just as easily as a silent one, study lead author Lynne Isbell from the University of California Davis explained to The Science Explorer that once an alarm call is given “other species are more vigilant, making it harder for leopards to hunt. They are stealthy hunters and typically use the element of surprise.”
When the monkeys were not lucky enough to spot one in time, the leopard would continue its approach, which probably ended badly for at least some of the monkeys. Another study has shown that roughly 11 percent of vervet monkeys at a nearby site are killed by predators each year, and hungry leopards are to blame for most of those deaths.
That is strong incentive for monkeys to sound their alarms when they notice a leopard on the prowl.
Listen to vervet monkeys emit their “leopard” alarm call here:
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