In the wild, monkeys need to watch out for all sorts of dangers，like leopards (豹），eagles and snakes. But the green monkeys studied by Julia Fischer of the German Primate Center have an additional challenge: they also have to scan the skies for drones (无人机). "Why do we fly a drone over green monkeys?" one may ask. The answer is that Fischer and her colleagues are interested in how monkeys communicate.
In a classic study back in the 1980s, scientists showed that African vervet monkeys (长尾黑频猴) produce alarm calls that are specific to the hunters they meet. For example，vervet monkeys hearing a leopard alarm might climb up a tree hurriedly, whereas the eagle call sends them running for cover under the closest bush.
Now，the green monkeys that live in Senegal share a similar system to warn of leopards and snakes. But they aren’t known to raise much noise in response to bird hunters. Therefore，the researchers decided to fly a drone over them. They treated 80 green monkeys to a show of drones. How did the animals react to these unfamiliar drones? “These monkeys did respond. And they responded with alarm calls，and they responded by running away,” Fischer said.
Here’s where things get really interesting: the calls the green monkeys made after spotting the drones were different from the ones they used to signal leopards or snakes. But what's even more interesting is that when the researchers did an analysis of the sound，they found that these alarm calls were almost strangely similar to the ones of the African vervets. And the findings are described in the journal Nature Ecology & Evolution.
The fact that the two monkey species seem to speak similar language, even though they separated from their last common ancestor some 3 million years ago，suggests that this kind of warning system is unchanged. So if you hear a monkey make alarm calls like that, watch out for a hungry bird, or check to see if your drone has delivered your package.
【小题1】What did the study in the 1980s find about vervet monkeys?| A．They could meet a variety of hunters in Africa. |
| B．They separated from their very close cousins early. |
| C．They could hide themselves very well from the hunters. |
| D．They made particular alarm calls according to the hunters. |
| A．By shouting and climbing up trees. | B．By making noises and playing dead |
| C．By sending alarms and running away. | D．By hiding themselves under shelters. |
| A．The alarm calls green monkeys made after spotting the drones. |
| B．The alarm calls the African vervets made after spotting the drones. |
| C．The alarm calls green monkeys used to signal leopards or snakes. |
| D．The alarm calls the African vervets used to signal leopards or snakes. |
| A．Survival of the Fittest— the Choice of Nature |
| B．The Application of Drones in Scientific Studies |
| C．Green Monkeys and Their Habits Are Back to Nature Finally |
| D．Green Monkeys and Their Cousins May Share Similar Language |
