When bonobos encounter a favorite food, like kiwi, they emit a series of long barks and short peeps. If that food is, say, an apple and not as well-liked, a bonobo makes other sounds, lower pitched yelps and peep-yelps. Researchers at the University of St Andrews in Scotland set out to discover whether other bonobos are able to extract information from those vocalizations. They studied four of the animals at the Twycross Zoo in central England.
The researchers started by training the bonobos that they would find kiwis on one side of their enclosure and apples on the other. In the morning, one group of animals would be let into the enclosure, and their responses to one of the fruits were recorded. That response was played later in the day when the second group of bonobos was let out. If the kiwi call was played, the bonobos were more likely to visit the kiwi side, and if the apple call was played, they were more likely to visit the apple side. If the call wasn't clear, then the animals were also more confused in their foraging.
"These animals are highly intelligent and this kind of study highlights their ability to extract meaning from listening to each other's vocalisations," study co-author Zanna Clay told BBC News.
This doesn't mean that bonobos have their own language---their communications lack syntax and structure---but "the way that the listening bonobos interpreted these sequences as meaningful shows some similarities with how we listen to language and understand it," Clay said.