University of St. Andrews researchers have discovered that chimpanzees in two nearby groups in Uganda’s Budongo Forest utilize leaf motions in several languages to communicate with one another.
A community of chimpanzees will employ their own preferred way of leaf-modifying motion, and nearby groups can use different ones, resulting in each group having its own gestural language, according to research published on Jan. 5 in Scientific Reports.
Chimpanzee social interactions include a significant portion of gestural communication. Chimpanzees utilize gestures to communicate with one another, ask for food, and settle disputes. Gestures may take many different forms: some require merely the hands, others require touching another individual, and yet others involve manipulating ordinary things like twigs, trees, and leaves that are present in chimpanzees’ natural surroundings.
For instance, leaf gestures might involve altering the leaves by tearing, ripping, or pulling them off the stem with a unique sound. These leaf-modifying motions, which are observed in practically all of the chimpanzee populations surveyed from East to West Africa, exhibit a striking resemblance to one another. However, for the first time, researchers have demonstrated that each group still uses a distinct dialect or style of leaf-modifying gestures, and that these distinctions cannot be explained simply by variations in their genetic profile or forest habitat.
Gal Badihi, the lead author, said that the various gestures employed by the two communities have similar contexts and appear to represent the same meanings, much like human dialects.
In both human and non-human animal societies, dialects are frequently seen as a fundamentally cultural element. While it has been demonstrated that chimpanzees are excellent at acquiring social skills—such as how to construct the correct tool—from one another, researchers have rarely discovered any evidence that their social environment also affects their communication. This new research reveals that chimpanzees socially learn some parts of their gestural communication, just as other skilled animal communicators like songbirds, whales, and humans.
Dr. Cat Hobaiter, a senior author, said that these behaviors are fairly common, but it can be difficult to detect the details in the dense forest, so they had to try their hand at some chimpanzee “archaeology.” The researchers would follow along and examine the leaf remains after the chimpanzees had performed their gesturing. The researchers could determine who was using either technique by examining the patterns that each type of leaf tearing left behind.
The researchers said that chimpanzees use these leaf-modifying motions for a variety of reasons, but the most common purpose chimpanzees in Budongo use them is as a sort of gestural “pick-up line”—similar to chimpanzee flirting; however, they also need to know how to do it in the local way.
The researchers also added that females who traveled across groups seem to comprehend the dialect of the new community. This demonstrates that throughout their lifespan, even as adults, chimpanzees may adaptably learn to speak and comprehend foreign languages.
Badihi, G., Graham, K.E., Fallon, B. et al. Dialects in leaf-clipping and other leaf-modifying gestures between neighbouring communities of East African chimpanzees. Sci Rep 13, 147 (2023). https://doi.org/10.1038/s41598-022-25814-x