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Why don't woodpecker brains get damaged from pecking? They're tiny, scientists say

AILSA CHANG, HOST:

A woodpecker's brain takes a big hit with every peck, but these birds don't experience brain damage. And NPR's Jon Hamilton reports on a team of scientists who think they have figured out why.

JON HAMILTON, BYLINE: The brain of a woodpecker goes through a lot.

(SOUNDBITE OF WOODPECKER PECKING)

HAMILTON: Just ask Sam Van Wassenbergh of the University of Antwerp in Belgium. He's been studying precisely what happens to a bird brain when beak eats wood.

SAM VAN WASSENBERGH: When you see these birds in action, hitting their head against the tree quite violently, then as humans, we start wondering how does this bird avoid getting headaches or brain damage?

HAMILTON: Scientists have been trying to answer that question for decades. And one very popular idea has been that the woodpecker's skull absorbs some of the shock to protect the brain inside. Van Wassenbergh wasn't convinced.

VAN WASSENBERGH: Nobody has ever explained it very well, in my opinion.

HAMILTON: So he and an international team decided they could do better using high-speed video.

VAN WASSENBERGH: We went to four different zoos in Europe where they had woodpeckers, and we recorded them at very high frame rates while they were pecking.

HAMILTON: Van Wassenbergh says the videos revealed some remarkable details.

VAN WASSENBERGH: They close their eyes at the moment they impact the wood. And this is to protect that there are any splinters that are jumping up the tree would hit their eyes.

HAMILTON: The videos also show that woodpeckers' beaks often get stuck in the wood. But a clever two-part design allows them to break free almost instantly. What the videos did not show is any sign that the woodpecker's brain is somehow cushioned.

VAN WASSENBERGH: The way we see the head behaving is very rigid, like you would use a hammer hitting wood.

HAMILTON: So the woodpecker's brain takes the full impact of every peck. Van Wassenbergh says that means the organ experiences deceleration five times higher than what it would take to cause a concussion in a human brain. But he says a woodpecker's brain is protected, not by cushioning but by its tiny size and weight.

VAN WASSENBERGH: An animal that has a smaller size, it can withstand higher deceleration. That's a biomechanical law.

HAMILTON: And he says a woodpecker's brain is about 700 times smaller than a human brain.

VAN WASSENBERGH: So that's why even the hardest hits that we observed are not expected to cause any concussion.

HAMILTON: Or even a headache. The study appears in the journal Current Biology. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.

Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.