Why Woodpeckers Don’t Mind Hitting Trees With Their Faces

Why Woodpeckers Don't Mind Hitting Trees With Their Faces
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When you watch a woodpecker repeatedly slam its face into a tree, it’s hard not to wonder how intact its brain is.

For years, the prevailing theory has been that the structures in and around the woodpecker’s skull absorb the impact of pecking. “Blogs and bulletin boards at zoos present it as fact – shock absorption occurs in woodpeckers,” he said. Sam Van Wassenbergh, a biologist at the University of Antwerp. Woodpeckers have even inspired engineering shock absorbing materials and equipment such as football helmets.

But now, after analyzing high-speed footage of woodpeckers in motion, Dr. Van Wassenberg and colleagues challenge this long-held belief. They found that woodpeckers don’t absorb shock when hammering and probably don’t get concussions using their heads as hammers. Their work was published Current Biology Thursday.

When a woodpecker hits a tree with its beak, it creates a shock. If something in the woodpecker’s skull absorbed these impacts before they reached the brain—the way a car’s airbag absorbs the shock before it reaches the passenger in a crash—then the woodpecker would decelerate more slowly on impact than with its beak.

Credit…Van Wassenbergh et al., Current Biology

With this in mind, the researchers analyzed high-speed videos of six woodpeckers (three species, two birds each) crashing into a tree. They traced two points on each bird’s beak and one point on its eye to mark the location of its brain. They found that the eye decelerates at the same rate as the beak, and in a few cases faster, which means that – at the very least – the woodpecker is not absorbing any impact when biting.

Dr. If woodpeckers were to absorb some of the impact they were trying to deliver to the tree, it would be a waste of valuable energy for the birds, Van Wassenberg said. Woodpeckers have evolved over millions of years to minimize shock absorption. Maja MielkeLike the hammer, the woodpecker’s skull is “really optimized for suction performance,” added the University of Antwerp biologist and co-author of the study.

But once one mystery was solved, another was revealed: how do woodpecker brains withstand repeated shock?

To calculate the pressure in the birds’ skulls, the researchers created a computational model based on breaststroke, skull shape and size, and they found that the pressure created was much lower than the pressure that would cause a concussion in a primate. In fact, the birds would have to hit the tree twice as fast as they are now, or hit the tree four times as hard, to get a concussion. “We forget that woodpeckers are much smaller than humans,” said Dr. Van Wassenberg said. “Smaller animals can withstand higher decelerations. Think of a fly that hits the window and then flies back again. “

“Traditionally, when people hypothesized about how animals function, they often didn’t even look at the living animal; they would just pull a bone out of the drawer,” he said Michael Granatosky who studies evolutionary biomechanics at the New York Institute of Technology and was not involved in the research.

Dr. Granatosky sees this work as an example of how much remains to be discovered. “There are all these things we think we know, but we don’t,” he said.

But the findings don’t answer all the questions about birds — like how a woodpecker maintains such rigidity between its skull and beak during pecking, and what other factors might be involved that might reduce possible damage to the brain.

“You have to think about the complexity of these systems Ryan Felice, an evolutionary biologist at University College London who was not involved in the research. “It’s not just bones and muscles, but maybe the amount of fluid in the brain and blood pressure, and even the ability to heal damaged neurons.”

Mrs. Mielke sees this work as a call to action for scientists in any field of research. “It’s always worth looking at things we think we already understand, because sometimes there can be surprises,” he said. “Intuition can deceive us.”

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