sciencetech-blog

comments

A dictionary that decodes the calls produced by gibbons is being developed by scientists.

Researchers at Wisconsin University in Madison have been using computer algorithms to analyse the whoops and songs produced by the apes.

Gibbons have one of the loudest calls in the natural world, creating whoops that can travel for miles through the dense the forests where they live in south east Asia.

The researchers studied the calls of white-handed gibbons like the one above to decode what the calls mean

Some species even have enlarged throat sacks that serve as a resonating chamber to amplify their call.

Now after hours of studying the animals, zoologist Dr Angela Dassow believes she can recognise what the gibbons are saying to each other.

Building on work started by primate biologist Dr Esther Clarke, from the University of St Andrews, she has identified 26 basic sounds like 'wa', 'hoo', 'oo' and 'waoo' that white handed gibbons use to communicate.

Working with Professor Michael Coen, a computer scientist at Wisconsin University, Dr Dassow is now attempting to unpick how these sounds are used to form rudimentary 'words' and 'phrases', much like in human language.

For example, a series of 'woos', 'hoos' are used by gibbons in the group to warn that a predator such as a leopard or snake is in the area.

Miss Dassow and Professor Coen have found that these calls also contain information about what the predator is doing - standing still, walking or climbing.

They have also found that dominant females also tend to use more of these basic sounds than others in the group and believe it may be because they are issuing instructions.

Speaking to New Scientist, Professor Coen said: 'If the predator is stationary, there's an extra "adjective" afterwards.

'A male may be saying, "We're being attacked", but the females are the alphas, so maybe they're the ones giving instructions on what to do.'

Writing in her PhD thesis, Dr Dassow added: 'Gibbon vocal productions that are unexpectedly governed by rules and statistical distributions common in human speech.'

Professor Coen and Dr Dassow created a computer algorithm that is able to analyse the sounds produced by the gibbons by measuring subtle variations in the frequency of the calls.

The technique, called Cepstral Self-Similarity Matrices, has enabled them to unpick the 'language' being used by white handed gibbons in far more detail than has been possible in the past.

White handed gibbons, like the one above, are endangered in the rain forests they inhabit in southeast Asia

The algorithm is able to detect 25 different sounds in this way.

However, while most humans would struggle to detect these subtlety different calls, Dr Dassow says he can hear 26 different sounds as the software fails to detect a variation in one of the calls.

Dr Dassow said: 'For example, predator alarm calls share basic properties, statistical phonemic distributions and overall structure but each displays unique sequences associated with a particular predator. 

'We view these as semantic units within the calls identifying the predator, as opposed to behavioral exhortations intended to trigger responses within the social group.' 

Professor Coen has also programmed a piano keyboard to play the different components of gibbon song, opening up the possibility of being able to 'talk' back to the gibbons. 

They have yet to test it as they have concentrated on predator warning calls and want to examine some of the more intimate interactions between the gibbons before they do.

The researchers hope to study the calls white handed gibbons like the one above in the wild in Thailand

An example of a white handed gibbon singing at while in an enclosure at a zoo

The researchers are also planning to apply the technique to other animals such as rats and dolphins in the hope of producing a kind of Rosetta Stone for animal communication.

They claim to have already identified 29 different sounds produced by rats.

Their work could also provide a new way of looking at how humans developed their own language skills.

Whoops and similar calls are thought to have been used by our ancestors to communicate before they developed more complex language.

Dr Esther Clarke, who first started the work studying the meanings of gibbon song and now works at Durham University, said: 'Not unlike humans, gibbons assemble a finite number of call units into more complex structures to convey different messages.

'Our data show that distant individuals are able to distinguish between different song types and infer meaning.'

A film of a white handed gibbons singing loudly at an animal park in Devon in 2011