If you think learning another human language lacks ambition, now is your chance to learn gibbon. A new paper in BMC Evolutionary Biology reveals the basics of gibbon language. Better still, this is an open access journal so all the information you need is ready and waiting.
There are four genus of gibbons, which means there is no more reason to assume there is a common gibbon language than there is to expect a single human tongue. The language Dr. Esther Clarke decoded for her doctorate belongs to the lar gibbon (Hylobates lar), of which there are five subspecies.
Clarke, now of Durham University, spent almost four months recording hundreds of what are known as “hoo” calls from gibbons in Thai forests. Unlike the gibbons' more famous loud songs, hoo calls sound like whispers to the human ear, and are therefore hard for us to distinguish. However, it has been suspected since the 1940s that gibbons use subtle differences in these calls to refer to different things. Clarke says the “quieter, close range vocalizations have received almost no empirical attention,” compared to their louder forms of communication.
The sounds were subjected to computer analysis to find patterns, and were then compared with careful records of events that happened before the calls to determine what might have inspired them. Clarke and her co-authors were able to identify hoo calls that related to foraging, predators, meeting the neighboring gibbons and even romantic duets.
The calls were found to display considerable subtly. For example, upon spotting a raptor (or model raptor), the gibbons made a shorter hoo at a lower frequency than any of their other calls. Raptors hear best at frequencies higher than even the normal hoo, but clearly the gibbons have learned not to take any chances. The adaptation of the use of pitch for context-specific calls is thought to have played a major part in the evolution of human speech, and Clarke's work suggests they may be more widespread than previously recognized.
"These animals are extraordinarily vocal creatures and give us the rare opportunity to study the evolution of complex vocal communication in a non-human primate. In the future, gibbon vocalizations may reveal much about the processes that shape vocal communication, and because they are an ape species, they may be one of our best hopes at tracing the evolution of human communication."
As well as helping to explain our own speech, an understanding of animal languages may help us see their world through their eyes, an extension of the observation that to truly understand a culture, one must learn to speak the language.
Last year saw the publication of a paper on the meaning of chimpanzee gestures, and scientists have now identified distinct regional dialects among Campbell's monkeys and even a possible elephant word for human. Nevertheless, Clarke's work makes lar gibbon one of the most documented animal languages.