Feature: The secret way gibbons of Thailand talk to each other revealed

The secret way a community of gibbons communicate with each other can provide vital clues on the evolution of human speech, a British academic revealed Wednesday.

Esther Clarke, a research fellow from Durham University, led a team that spent months studying the way a community of white-handed or lar gibbons (Hylobates lar) in Thailand converse with each other.

For the first time, researchers were able to interpret the meaning of distinct whispers or 'hoo' calls made by gibbons using sophisticated technology.

Their report, published in the British-based journal BMC Evolutionary Biology, reveals the 'hoo' calls are a distinctive form of communication, responding differently to particular events, even alerting group members about predators such as tigers and snakes.

They say acoustic variations they detected in gibbon 'hoos' may be similar to human speech in the way sound and pitch are important carriers of meaning.

In their report, the team say while gibbons are mainly known for their loud and conspicuous songs, they can also produce a number of soft call types known as 'hoos'.

These subtle calls have been alluded to in studies dating back to 1940, but due to the volume of gibbons' voices, they are virtually indistinguishable to the human ear and have been difficult to record and analyze.

Researchers used modern recording technology and computer analysis to interpret the meanings of the distinct hoo calls.

Clarke said: "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. Gibbon vocalizations may reveal much about the processes that shape vocal communication, and because they are an ape species, may be one of our best hopes at tracing the evolution of human communication."

The research team spent almost four months following lar gibbon groups around the forests of North-eastern Thailand, extracting over 450 hoo sounds which were then put through computer analysis.

The team investigated responses to a range of predators, including clouded leopards, tigers, pythons, and raptors, including eagle owls and crested serpent eagles.

Clarke, from the Evolutionary Anthropology Research Group at Durham University, added: "The gibbons produced individual hoo calls for different contexts, including foraging, predator detection, encountering neighbors, and as part of duet songs by mated pairs."

The researchers say their study will be of direct relevance to the debate about the evolution of human speech, demonstrating the ability of gibbons to produce context-specific calls as a necessary communication tool when attention is being drawn to something specific happening. Endit