There are plenty of reasons to bang your head against a wall these days. But if you do, maybe don’t look to the woodpecker for inspiration. Scientists have long hypothesized that a spongy bone in the woodpecker’s skull cushions its repeated head slams like a well-designed safety helmet. (Indeed, engineers have modeled football helmets and shock-absorbing electronics after this idea.) But a new analysis shows the birds may be opting for power over protection. “Many studies heavily assume that there must be some sort of shock absorption—really because if we did something like that, we would need it,” says Thomas Roberts, a biomechanist at Brown University who was not involved in the research. “This study was really an advance because they put real data to the question.” Whether digging for food, constructing housing, or luring mates, woodpeckers bang their heads into trees about 20 times per second. And then they go about their day. When a football player rams into an opponent, their head comes to a stop but their brain continues forward, compressing in the front and stretching in the back, sometimes damaging the brain . But woodpeckers, despite smacking with accelerations three times the human concussion threshold, seem to escape unharmed, says Sam Van Wassenbergh, a biomechanist at the University of Antwerp and lead author on the study. This impressive resilience led previous researchers to search for a specialized structure protecting the birds. Some hypothesized its spongy skull bone could act as an airbag , whereas others proposed its elongated tongue could be a seatbelt for the brain . Van Wassenbergh and his colleagues took another approach: They analyzed whether the pecking birds were really cushioning their blows. The researchers recorded 109 high-speed videos of six woodpeckers from three species: the black woodpecker ( Dryocopus martius ), the pileated woodpecker ( D. pileatus ), and the great-spotted woodpecker ( Dendrocopos major ). Tracking points on their beaks and heads as the animals pecked on wood, the scientists found that all the woodpecker skulls remained stiff —that is, their heads didn’t come to a halt any slower than their beaks, the team reports today in Current Biology . A simulation based on the recordings showed adding shock absorption wouldn’t actually help protect the birds’ brains. If its head absorbed part of the impact, the bird couldn’t exert as large a force—meaning the woodpecker would peck less wood. In order to penetrate to the same depth with shock absorption, the birds would have to headbang harder, counteracting any built-in protection. Tracking points on the heads and beaks of woodpeckers shows the birds aren’t cushioning their blows. Van Wassenbergh et al ., Current Biology 2022 “The take-home makes a lot of sense,” Roberts says. “If you’re driving a nail with a hammer, you don’t want to put a pillow between the hammer and the nail.” So how does the woodpecker avoid concussions? The size and orientation of the bird’s brain safeguard it, the authors say. Even the strongest of wood pecks left the bird brains with less than 60% of the pressure needed to give a human brain a concussion. In addition, woodpeckers may contain specialized mechanisms to prevent and repair minor brain trauma . Some scientists aren’t ready to rule out the bird’s built-in pillow quite yet. Jae-Young Jung, a biomedical engineer at the University of California, San Francisco, notes that woodpeckers are known to brave opponents tougher than wood—including metal poles. Although he agrees the birds appear not to employ shock absorption for everyday hammering, he suggests they may need it for other scenarios. Still, he says, the study “will open up new questions and new ideas about how woodpeckers really do their job.” And it shows yet again how impressively adapted the birds are to their behaviors. As for humans, our big brains aren’t cut out for conking, no matter how frustrated we get. So, you should probably stick to wearing a helmet.
Published in: "Science".