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If you’ve ever watched a woodpecker at work,
you may have found yourself wondering how a bird can repeatedly
pound their head against tree trunks without damaging their brains in the process.
Well you would not be the only one to wonder this.
Scientists have spent a lot of time investigating this question,
and they don’t always arrive at the same conclusion.
There are several hypotheses floating around,
and the leading one is that woodpecker skulls
act like little shock-absorbing helmets.
We’ve even made a video about that.
But as the research rolls in, it looks like their skulls
don’t do much of any shock absorbing.
Instead, their skulls come with a whole assortment of specialized features…
to let them both take a proverbial punch, and deliver one.
Newton’s first law of motion tells us that objects in motion like to stay in motion,
so when a moving head smashes into a tree, the brain inside wants to keep going.
And that energy can send the brain bouncing around
inside the skull for a little while longer, too.
In a human, this would most likely lead to a concussion.
But woodpecker skulls are not built like my skull.
The front of them is made of a spongy kind of bone,
which scientists hypothesized acted as a shock-absorbing material
that kept the birds safe.
But there’s another one of Newton’s laws that gets in the way of that hypothesis.
Every action comes with an equal and opposite reaction.
If a woodpecker’s skull were absorbing the brunt of the impact,
that would also mean that the skull is applying less force to the tree.
And that’s not what they want.
In order to make that hole, woodpeckers would have to work
even harder than their tiny heads already do.
Back in July 2022, one team used high-speed videos of three different woodpecker
species to confirm that there was basically no shock absorption going on.
Instead, they found that woodpecker heads are specialized to
deliver as much force into their pecking target as possible.
In other words, these birds come equipped with built-in hammers.
But that also means that an equal force is being delivered back into their heads.
So how are their brains surviving all of this pecking?
It seems to be a combination of a few factors.
For one, woodpecker skulls are pretty small.
Researchers estimated that if their heads were larger, the amount of pressure
each peck would exert on the brain could be enough to cause a concussion.
The team also hypothesized that woodpeckers protect their brains
by not pecking too quickly, and not pecking wood that’s too stiff.
Meanwhile, that patch of spongy bone is there to add a little bit of elasticity
so that part of the skull is less likely to shatter on impact.
But other research has clarified the role of the skull’s unique structure…
not just having a bit of spongy bone, but the fact that different parts of the skull
have different mineral compositions and bone densities.
In a different study, another team of scientists 3D printed several models
of woodpecker skulls, and then smashed them into a metal target
to reproduce what they called a “worst-case scenario”.
Based on those experiments, it appears the skull’s internal structure helps
redirect the equal and opposite force that the birds generate while pecking.
That force gets converted into a pressure wave that travels through their heads.
But instead of heading toward the brain cavity, the waves are sent down
through what’s known as the jugal bone at the bottom of the skull.
The team also observed how the skulls move
through 3-dimensional space in response to a collision.
It turns out that movement can help dampen the specific pressure waves
that would be most harmful to a woodpecker brain.
You know how like if you move back and forth in a bathtub at just the right speed
you can get the water sloshing so intensely that
a bunch of it will just spill out of the bathroom floor?
Or how about, like, finding just the right note to make a wine glass shatter?
These are the result of resonance frequencies, which are specific frequencies
that amplify the movement of whatever the wave is moving through.
Every object has a set of resonance frequencies
that are determined by what it’s made of and its shape.
And that includes objects like wine glasses and bathtubs,
and also bird brains and skulls.
So if the pressure wave traveling through a woodpecker’s head
has the same frequency as one of the head’s resonance frequencies,
the brain could start sloshing around until it smashes into the skull.
The woodpecker wants to avoid that happening,
so it can move its head during the peck to try and cancel out
any pressure wave that matches its head’s resonance frequencies.
In fact, their relatively small brain cavities may help with that, too,
by keeping any brain sloshing to a minimum.
It’s harder for the brain to build up the speed it needs
to produce a concussion-grade smash.
And there may be other ways a woodpecker’s specialized biology keeps it healthy.
Like, these birds might have a way to pinch off the veins in their necks to
build up some blood-based padding up in there.
Or they might have special proteins in their brains that help repair damage.
So it’s really far too simple to say that woodpeckers
come pre-equipped with fancy helmets.
At the very least, they’re more like fancy helmets with a built-in hammer.
I guess it shows just how complicated nature can get
when there is a very specific and important job to do.
And if these woodpeckers were to read Annie Murphy Paul’s book,
“The Extended Mind,” they will probably be relieved to learn that thinking
can go beyond the brain and doesn’t have to stay within the confines of a skull.
You might be thinking, “woodpecker’s can’t read!”
Well then it’s a good thing that Blinkist also has an audio version of the book
available to download and listen to offline, because I know your next concern
would be the woodpecker’s have a lack of consistent internet access.
None of that is a problem when you use Blinkist, an app that takes the best insights
and need-to-know information from over 5,000 nonfiction books and podcasts
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