Scientists recently discovered that chimpanzees will send out exaggerated warning calls and gestures to other members of their group in dangerous situations—similar to the way humans behave. While we knew for some time that chimps tend to “look out for each other,” the new study revealed that the signals being used are more sophisticated that we once thought.
Previous research revealed that chimps in experiments with humans would modify their communication tactics for food depending on how the person feeding them was interacting. They would vocalize more if the human’s back was turned or gesture more if they were forward-facing. In the new study, researchers tested whether this same complex communication would be used to express a threat from a predator.
They modeled snakes from wire and plaster and painted them to resemble a local viper, concealing them where chimpanzees were likely to encounter them. In the first experiments, the scientists simply observed the chimps interact with the “snake” and each other. Chimps responded with an “alert hoo” and some used “marking” to show chimps where the threat was located.
In the next set of experiments, the researchers used concealed speakers to play recorded chimpanzee calls—either a “rest hoo” or the alert hoo. If the chimp heard a rest hoo before seeing the snake, their hooting and marking were more persistent. Because that increased reaction had no benefit to the signaler, scientists concluded that they were exclusively trying to help the chimps they heard but could not see.