Woodpeckers' heads look more like stiff hammers than hard hats

Woodpeckers’ heads look more like stiff hammers than hard hats

Frame sequence from a high-speed video of pecking by the Helmeted Woodpecker (Dryocopuspileatus). Photo credit: Erica Ortlieb & Robert Shadwick (University of British Columbia)

Scientists have long wondered how woodpeckers can repeatedly bang their beaks against tree trunks without damaging their brains. This led to the notion that their skulls should act like shock-absorbing helmets. Researchers are now reporting in the journal Current Biology on July 14 have refuted that notion, saying their heads look more like stiff hammers. In fact, their calculations show that any shock absorption would affect the woodpeckers’ ability to peck.

“By analyzing high-speed videos of three woodpecker species, we found that woodpeckers do not absorb the shock of impact with the tree,” says Sam Van Wassenbergh of Universiteit Antwerpen, Belgium.

Van Wassenbergh and colleagues first quantified the impact delays during pecking in three woodpecker species. They used the data to build biomechanical models, leading them to conclude that any shock absorption of the skull would be detrimental to the birds.

Slow-motion clips of high-speed video of head impact during pecking (Dendrocopos major, Dryocopuspileatus, and Dryocopus martius illustrate the anatomical landmarks tracked in the kinematic analysis). Recognition: Current Biology/Van Wassenberg het al

But if their skulls aren’t acting as shock absorbers, does the angry pecking endanger their brains? It turns out that is not the case. While the deceleration shock with each pick exceeds the known threshold for concussion in monkeys and humans, the woodpeckers’ smaller brains withstand it. Van Wassenbergh says that woodpeckers can make a mistake if, for example, they peck at metal with full force. But their usual log pecking is generally well below the threshold to inflict concussion, even if their skull doesn’t act as a hard hat.

“The lack of shock absorption doesn’t mean their brains are at risk during what appears to be violent impacts,” says Van Wassenbergh. “Even the strongest shocks from the more than 100 analyzed picks should still be safe for the woodpecker’s brain, as our calculations have shown that the brain load is lower than that of people who suffer a concussion.”

The results disprove the long-held theory of shock absorption that’s been popularized in the media, books, zoos and more, says Van Wassenbergh. “While filming the woodpeckers in zoos, I’ve seen parents explain to their children that woodpeckers don’t get headaches because they have shock absorbers built into their heads,” he says. “This shock absorption myth in woodpeckers is now shattered by our results.”

From an evolutionary perspective, the results could explain why there are no woodpeckers with much larger heads and neck muscles. While a larger woodpecker might provide more powerful picks, concussions would likely cause him major problems.

The findings also have some practical implications, he adds, as engineers have previously used the anatomy of the woodpecker’s cranial skeleton as a source of inspiration for the development of shock-absorbing materials and helmets. The new findings show that this isn’t such a good idea, as the woodpecker’s anatomy minimizes shock absorption.

Van Wassenbergh notes that another recent study by his team showed that woodpeckers’ beaks often get stuck, but the birds quickly free themselves by alternately moving the top and bottom halves of their beak. They are now investigating how the beak shape adapts to pecking.

How do woodpeckers avoid brain injuries?

More information:
Sam Van Wassenbergh, Woodpeckers minimize cranial shock absorption, Current Biology (2022). DOI: 10.1016/j.cub.2022.05.052. www.cell.com/current-biology/f… 0960-9822(22)00855-7

Quote: Woodpeckers’ Heads Act More Like Stiff Hammers Than Safety Helmets (2022, July 14), retrieved July 14, 2022 from https://phys.org/news/2022-07-woodpeckers-stiff-safety-helmets.html

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