Sunday, April 15, 2012

China - How Does A Woodpecker Avoid Brain Injury?

Chinese scientists have unraveled answers to a long-standing question – how do woodpeckers avoid head injury when they peck on wood at such high speed and frequency?

Professor Fan Yubo, together with colleagues from Beihang University and Wuhan University of Technology, believe that the woodpecker’s excellent resistance to head injury may be due to its distinctive cranial and beak bone structure and composition.

Head injury, caused by a sudden impact or by a change in the linear or angular velocity of the head, is estimated to account for 15 percent of the overall burden of fatalities and disabilities in people.

Unlike humans, woodpeckers are clearly adapted to managing impact forces, allowing them to peck rapidly without incurring brain or eye injury.

This intriguing ability has attracted wide attention not only by ornithologists and biologists, but also by researchers in the mechanical and electronic sciences.

Previous studies suggested that impact injury to the brain might be avoided by powerful muscles, or by drilling behavior, or by a special orientation of the brain within the skull compared with humans. However, there have been few systematic analyses of the properties of woodpecker’s skull.

In a study published in the journal Science China Life Sciences, the research team investigated the properties of the woodpecker’s cranial bone and beak – a remarkable example of nanofabrication and self-assembly perfected by millions of years of evolution.

The team also compared the woodpecker’s cranial bone and beak structure against that of the lark, a bird that does not exhibit the same pecking action on wood.

They found that the ultimate strength of woodpecker’s cranial bone was markedly higher than that of the lark; more plate-like spongy bone was present in the cranial bone of the woodpecker, while the cranium of the lark contained more rod-like structures.

The larger number of plate-like structures, greater thickness and numbers of trabeculae, and the closer spacing between individual trabeculae in the woodpecker cranial bone allows the bird to resist deformation during pecking, decreasing the stress on the brain.

Hence, taken together, the woodpecker’s unique cranial bone achieves a higher ultimate strength and resistance to impact injury compared with the lark.

The authors hope that the information gleaned from this study may someday inspire the design and optimization of protective headgear for humans.

Juliana Chan 

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