Taking a Pounding: How Woodpeckers Avoid Concussions

I recently watched a woodpecker pound its beak against the metal edge of a building. A woodpecker finds a suitable tree (or in my bird’s case, a piece of metal) that greatly amplifies its drumming. They need to be heard throughout their territory so they can attract females and warn other males to stay away. As a birdwatcher, I take this territorial drumming for granted. But as someone interested in learning from nature, I have to be impressed that these birds don’t give themselves traumatic brain injuries.

A woodpecker drums 18 to 22 times per second with a deceleration of 1200 G’s. For comparison, that’s more than 12 times the G-force that results in a brain concussion for a human. Four recently added strategies on AskNature describe woodpecker adaptations that collectively protect the brain from injury.

Each adaptation or strategy can inspire ways to prevent impact and vibration damage to devices such as micro-machined electronics, computer casings, bicycle helmets, children’s car seats, wheelchairs, car and truck bumpers, high speed boat hulls and their occupants, shoes to protect knees and joints — especially for people suffering from arthritis — and packaging to protect all breakable items such as glass, eggs, etc.

One woodpecker strategy has to do with beak shape and its material composition. A second strategy is the combination of the small volume of the woodpecker’s cranial space and the smooth surface area of the brain. A third strategy uses a plate-like spongy bone in the frontal area of the skull itself to absorb shock. The last strategy features a long, flexible bone that wraps around the head of the woodpecker and secures and directs vibrational forces away from the brain.

I’m just going to talk about the first strategy and show how, when you do biomimicry, you can take a biological strategy and translate it into something a designer or engineer can use.

As explained on AskNature, the woodpecker’s beak is comprised of two layers: An inner layer of strong, dense bone and an outer layer of more flexible material. The outer layer is the first to encounter any impact forces. The flexible tissue allows the beak to bear high amounts of stress and reduces the risk of shock by bending and flexing with each vibrational transmittance. Once forces reach the hard bone, the upper beak intersects with a very thin, long bone called the hyoid bone that goes over and behind the skull. Forces then travel along the hyoid bone, diverting around the skull and back out through the tongue.

As forces continue to travel along the upper beak, those that have not been diverted then encounter the lower beak. Following the path of least resistance, vibrational forces follow the downward slope of the beak’s shape and away from the cranial space where the brain is.

In biomimicry, it’s important to take that kind of biological information and put it into non-biological terms. We call that restatement a “design principle.”

So, here’s how I interpret this woodpecker strategy as a design principle: Protection from impact, particularly from sudden horizontal forces applied to one end of a structure, can be achieved by having a structure made up of an outer flexible layer and an inner, stiffer layer. When a rapid horizontal force is applied perpendicular to the end the structure, the force is absorbed by the flexible layer first, and then transferred to the inner, stiff layer. From there, the force is diverted upward and downward where it dissipates.

The biology is gone and it’s now in terms that might not scare off a designer. That amount of detail might be enough or some applications, like for use on the protective casing of a laptop computer. However, for something more complicated, like a bicycle helmet designed to protect your own brain, a more detailed design principle might be valuable, such as one that includes the description of the long, flexible bone.

Biomimicry is a multidisciplinary process. The biologist helps others on the team understand the biology, but developing the design principle and coming up with possible applications works best with the other disciplines involved. I presented these four strategies to biomimicry practitioners on one of the biomimicry LinkedIn groups and they came up with most of the potential applications mentioned earlier in the article. I’d love to hear your ideas for this or the other three strategies.