The latest studies by an international team of researchers show that the previous assumption that a woodpecker's skull acts as a shock absorber is incorrect. On the contrary: woodpecker skulls are evolutionarily optimized to function as energy-saving hammers without this leading to serious brain injuries. In addition to gaining scientific knowledge, these new research results are likely to have consequences for materials researchers and product developers all over the world ( HERE ).
Woodpeckers do hard work
Anyone who sees woodpeckers in action will ask themselves the same question. How do they manage to hammer a tree with their beak at this extremely high frequency without sustaining serious head injuries or at least developing headaches?
The raw numbers are extremely impressive: To build nesting holes, find food, mark their territory or attract a mate, the small birds hit the tree at a speed of 25 km/h, around twenty times per second and around 12,000 times during the day. ( HERE )
And with every single blow, the head is decelerated with a thousand times the acceleration due to gravity. ( HERE )
So much for the numbers. But how does this work without serious negative consequences for the bird?
Head should act like a shock absorber
For many years, researchers have agreed that a woodpecker's skull acts like a shock absorber, and the structures in the woodpecker's skull absorb the shock. This is intended to minimize the damaging slowdown of the woodpecker's brain when it hits trees.
HERE , Korean researchers recently provided evidence for the previously valid hypothesis that spongy structures, so-called cancellous bone, can be found in strategic places in the skull, which cushion the impact. The cancellous bone provides a lightweight supporting structure in the bone that is stable against pressure loads. This declaration has influenced the development of shock-absorbing materials and products worldwide.
This explanation was reinforced by a 2020 study by Chinese researchers, according to which the woodpecker's hyoid bone, a bone between the beak and the skull. It is said to have a similar effect as it absorbs some of the energy. ( HERE )
This explanation of the skull as a shock-absorbing shock absorber can be found worldwide on display boards in zoos or in school textbooks and was considered to be sufficiently scientifically proven. Until now!
New study: Woodpecker head is not a shock absorber
In mid-July 2022, a multinational team led by biologist Sam van Wassenbergh from the University of Antwerp published a study that turns previous thinking on its head. The research group concludes that the shock absorber hypothesis is even paradoxical, as this mechanism of action “would probably impair the bird’s striking performance.” In short, if the kinetic energy were absorbed, the woodpecker would not be able to peck at the tree trunk with such force.
In the current study, hammering by three different woodpecker species was quantitatively examined. High-speed recordings in which key points on the woodpecker's head were marked with markings showed that the area between the beak and the skull remains stiff and therefore does not have a dampening effect. However, if a structure in the woodpecker's head absorbed the kinetic energy, the woodpecker's head would have to decelerate more slowly than the beak upon impact and everything would have to slide into one another. However, this is not the case, as the video recordings impressively show. (Source: University of Antwerp )
On the contrary, the construction of a woodpecker's head acts like a stiff hammer to transfer maximum energy to the tree trunk. Lt. According to Prof. Wassenbergh, the shock-absorbing effect would be a complete waste of energy and why should evolution produce such an inefficient solution?
“The biomechanical model showed that a build-in shock absorber is just a waste of precious energy for the bird.”
Sam van Wassenbergh ( HERE )
Hammer mechanism
Modeling the effects of cranial shell size and shape on intracranial pressure shows that woodpeckers' brains are still safe from concussion well below the concussion threshold known for primate brains when hammering on a tree trunk ( HERE ). In biomechanical simulations, the research team was able to show that the system consisting of head and beak functions like a stiff hammer. And although the birds peck at the tree trunk with enormous frequency and persistence, the shock that their brain has to withstand is harmless.
How does the woodpecker protect itself?
But if the hypothesis of the shock-absorbing mechanism in the woodpecker skull has now been refuted, the question remains, how does the bird protect itself?
This is where boring mathematics and physics come into play. The researchers created a calculation model and entered all the data they knew about the pecking movement, skull shape and size, etc. The result was surprising. Contrary to what we would expect from our human perspective, they found that the pressure on the skull caused by hammering is far below what would cause a concussion in a human or other primate.
Miracle brain
The reason lies in the brain itself. It is extremely small and light and therefore hits the skull bone with significantly less force in the event of an impact than would be the case with a primate such as humans. The simulations showed that, due to its small mass, the brain only hits the inside of the skull with 39 to 60 percent of the force as it would in a comparable situation in humans.
So the birds would have to pound twice as fast or the surface of the tree would have to be four times as hard for them to suffer a concussion. But evolution wisely prevented this because there are no woodpeckers with larger heads or stronger neck muscles. Woodpeckers are anatomically incapable of exerting themselves to such an extent that they cause themselves a concussion.
“We forget that woodpeckers are significantly smaller than humans. Smaller animals can withstand higher delays. Think of a fly hitting a window and then just flying back again.”
Sam van Wassenbergh ( HERE )
And what does that mean for the engineers?
The new findings clearly show that the woodpecker is not a suitable role model to inspire engineers or product developers in the development of shock-absorbing materials, materials or equipment such as bicycle helmets. A cyclist's skull cannot be adjusted at short notice. Creativity is now required to find other examples in our magnificent flora and fauna from which important lessons can be drawn that can be implemented in application research.
Source: National Geographic , Germanic News , cell.com , cell.com , Taylor&Francis online , IOP Science ,
You might also be interested in : The photo of the “man-sized” flying fox (fact check)
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Notes:
1) This content reflects the current state of affairs at the time of publication. The reproduction of individual images, screenshots, embeds or video sequences serves to discuss the topic. 2) Individual contributions were created through the use of machine assistance and were carefully checked by the Mimikama editorial team before publication. ( Reason )

