Oldest bird hears like an emu

14 January 2009

The earliest known bird, Archaeopteryx, had hearing similar to an emu, Natural History Museum scientists report today.

A reconstruction of an Archaeopteryx

A reconstruction of an Archaeopteryx

They demonstrate that Archaeopteryx was more bird-like than reptilian - this ancient bird had some dinosaur-like features and may be the link between dinosaurs and birds.

The research shows for the first time how the length of the inner ear of birds and reptiles can be used to accurately predict their hearing ability. This could help us understand more about how hearing evolved.

CT scans of inner ear

The team used a CT scanner to accurately reconstruct the inner ear anatomy of various intact bird and reptile specimens. They studied 59 species of bird and reptiles including lizards, raven, gecko and owl (an owl example is shown at the top of the page).

CT scan image of barn owl skull showing inner ear, coloured orange

CT scan image of barn owl skull showing inner ear, coloured orange

Museum palaeontologist, Dr Paul Barrett, explains, ‘In modern living reptiles and birds, we found that the length of the bony canal containing the sensory tissue of the inner ear (cochlea duct) is strongly related to their hearing ability.’

Animals with a long cochlea duct tend to have the best hearing and vocal ability and modern birds have relatively longer ones than living reptiles.

Predicting hearing ability in extinct animals

Barrett continues, ‘We were then able to use these results to predict how extinct birds and reptiles may have heard, and found that Archaeopteryx had an average hearing range of approximately 2,000 Hz.’

‘This means it had similar hearing to modern emus, which have some of the most limited hearing ranges of modern birds.’

Previously, scientists could only estimate how extinct animals may have heard by comparing the brain region size from damaged fossil skulls with their modern-day counterparts.

Museum palaeontologist Dr Stig Walsh adds, ‘By examining the 3D CT scans we were able to see for the first time the real relationship between hearing ability and behaviour in extinct reptiles and birds.’

Bird-like Archaeopteryx
Rare fossil archaeopteryx looked after at the Museum

Rare fossil archaeopteryx looked after at the Museum

Archaeopteryx lithographica was a magpie-sized insect-eating bird with feathers and dinosaur-like features such as teeth, a long bony tail and clawed hands. It is the first known bird, living around 147 million years ago during the Upper Jurassic period.

Museum palaeontologist Dr Angela Milner explains how this research adds yet more information about how bird-like Archaeopteryx was.

‘Our previous research has shown that the part of the ear that controls balance was just like that of modern birds. Now we know that Archaeopteryx had bird-like hearing, too.’

Hearing, habitat and behaviour

A long cochlea duct also indicates that an individual uses complex vocal communication. This suggests that it lives in groups and may also influence habitat choice. This is true for both mammals and birds.

‘Species living in large social groups have more complicated vocal communication which is understandably influenced by an individual’s ability to hear,’ says Dr Barrett.

‘Species living in a closed environment, such as forests, where visual communication is ineffective often possess more complex vocal abilities, so now we can more accurately predict the habitat types that extinct animals lived in by examining their ability to hear and communicate,’ Dr Barrett concludes.

The research received funding from the Natural Environment Research Council (NERC) and is published in the latest issue of the Proceedings of the Royal Society B.

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