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Why Don't Woodpeckers Get Brain Damage?

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Hit your head really hard on something, and it’ll smart for a while. In worse cases, you might get a concussion, fracture your skull, or receive a brain injury that leaves you impaired or kills you (traumatic brain injuries account for nearly one third of injury-related deaths in the US).

Good thing you’re not a woodpecker, then. The lives and livelihoods of these birds revolve around slamming their heads into things. Whether it wants to get at an insect hiding in bark, excavate a space to build a nest, claim a bit of territory, or attract a mate, the woodpecker has one simple solution: bang its head against a tree trunk at speeds reaching 13 to 15 miles per hour. In an average day, a woodpecker does this around 12,000 times, and yet they don’t seem to hurt themselves or be the least bit bothered by it. This is because, after millions of years of this type of behavior, they’ve evolved some specialized headgear to prevent injuries to their heads, brains, and eyes.

To figure out what goes into woodpecker head trauma prevention, a team of Chinese scientists took a look at the birds’ skulls and brains and their pecking behavior. They watched as woodpeckers pecked at force sensors while recording them with high-speed cameras so they could see the strikes in slow motion and know how hard each blow was. They also scanned the birds’ heads with x-rays and an electron microscope to get a better look at their bone structure. Finally, they squished a few preserved woodpecker skulls in a material testing machine and, using their scans, built 3D computer models of the birds’ heads to smash in a simulation.

When all was said and done and both the virtual and actual woodpeckers' heads had taken a sound beating, the researchers found that there are a few anatomical features and other factors that come together to keep a woodpecker safe and healthy while it rat-a-tat-tats the day away.

First, a woodpecker’s skull is built to absorb shock and minimize damage. The bone that surrounds the brain is thick and spongy, and loaded with trabeculae, microscopic beam-like bits of bone that form a tightly woven “mesh” for support and protection. On their scans, the scientists found that this spongy bone is unevenly distributed in woodpeckers, and it is concentrated around the forehead and the back of the skull, where it could act as a shock absorber.

Woodpeckers' hyoid bones act as additional support structures. In humans, the horseshoe-shaped hyoid is an attachment site for certain throat and tongue muscles. Woodpeckers’ hyoids do the same job, but they’re much larger and are differently shaped. The ends of the “horseshoe” wrap all the way around the skull and, in some species, even around the eye socket or into the nasal cavity, eventually meeting to form a sort of sling shape. This bizarre-looking bone, the researchers think, acts like a safety harness for the woodpecker’s skull, absorbing shock stress and keeping it from shaking, rattling and rolling with each peck.

Inside the skull, the brain has its own defenses. It’s small and smooth, and is positioned in a tight space with its largest surface pointing towards the front of the skull. It doesn’t move around too much, and when it does collide with the skull, the force is spread out over a larger area. This makes it more resistant to concussions, the researchers say.

A woodpecker’s beak helps prevent trauma, too. The outer tissue layer of its upper beak is longer than the lower beak, creating a kind of overbite, and the bone structure of the lower beak is longer and stronger than the upper one. The researchers think that the uneven build diverts impact stress away from the brain and distributes it to the lower beak and bottom parts of the skull instead.

The woodpecker’s anatomy doesn’t just prevent injuries to the brain, but also its eyes. Other research using high-speed recordings has shown that, in the fraction of a second just before their beaks strike wood, woodpeckers’ thick nictitans—membranes beneath the lower lid of their eyes, sometimes called the “third eyelid”—close over the eyes. This protects them from debris and keeps them in place. They act like seatbelts, says ophthalmologist Ivan Schwab, author of Evolution's Witness: How Eyes Evolved, and they keep the retina from tearing and the eye from popping right out of the skull.

There’s also a behavioral aspect to the damage control. The researchers found that woodpeckers are pretty good at varying the paths of their pecks. By moving their heads and beaks around as they hammer away, they minimize the number of times in a row that the brain and skull make contact at the same point. Older research also showed that the strike trajectories, as much as they vary, are always almost linear. There’s very little, if any, rotation of the head and almost no movement immediately after impact, minimizing twisting force that could cause injury.

Earlier this year, another group of researchers in China found that, with all of these adaptations, 99.7 percent of the impact energy from striking a tree is absorbed by the body, but a little bit—that last 0.3 percent—does go to the head and the brain. That mechanical energy gets converted into heat, which causes the temperature of a woodpecker’s brain to increase, but the birds seem to have a way dealing with that, too. Woodpeckers usually peck in short bursts with breaks in between, and the researchers think that these pauses give the brain time to cool down before the head banging starts again and brings the temperature back up.

This story was originally published in 2012. It was updated with new information in 2014.

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Big Questions
Where Should You Place the Apostrophe in President's Day?
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Happy Presidents’ Day! Or is it President’s Day? Or Presidents Day? What you call the national holiday depends on where you are, who you’re honoring, and how you think we’re celebrating.

Saying "President’s Day" infers that the day belongs to a singular president, such as George Washington or Abraham Lincoln, whose birthdays are the basis for the holiday. On the other hand, referring to it as "Presidents’ Day" means that the day belongs to all of the presidents—that it’s their day collectively. Finally, calling the day "Presidents Day"—plural with no apostrophe—would indicate that we’re honoring all POTUSes past and present (yes, even Andrew Johnson), but that no one president actually owns the day.

You would think that in the nearly 140 years since "Washington’s Birthday" was declared a holiday in 1879, someone would have officially declared a way to spell the day. But in fact, even the White House itself hasn’t chosen a single variation for its style guide. They spelled it “President’s Day” here and “Presidents’ Day” here.


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Maybe that indecision comes from the fact that Presidents Day isn’t even a federal holiday. The federal holiday is technically still called “Washington’s Birthday,” and states can choose to call it whatever they want. Some states, like Iowa, don’t officially acknowledge the day at all. And the location of the punctuation mark is a moot point when individual states choose to call it something else entirely, like “George Washington’s Birthday and Daisy Gatson Bates Day” in Arkansas, or “Birthdays of George Washington/Thomas Jefferson” in Alabama. (Alabama loves to split birthday celebrations, by the way; the third Monday in January celebrates both Martin Luther King, Jr., and Robert E. Lee.)

You can look to official grammar sources to declare the right way, but even they don’t agree. The AP Stylebook prefers “Presidents Day,” while Chicago Style uses “Presidents’ Day.”

The bottom line: There’s no rhyme or reason to any of it. Go with what feels right. And even then, if you’re in one of those states that has chosen to spell it “President’s Day”—Washington, for example—and you use one of the grammar book stylings instead, you’re still technically wrong.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
How Do You Steer a Bobsled?
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Quinn Rooney, Getty Images

Now that the Olympics are well underway, you might have developed a few questions about the games' equipment. For example: How does one steer a bobsled? Let's take a crack at answering this pressing query.

How do you steer a bobsled?

Bobsled teams careen down an icy, curving track at up to 90 miles per hour, so steering is no small concern. Drivers steer their sleds just like you steered your childhood sleds—by manipulating a pair of ropes connected to the sled's steel runners. The driver also gets help from the rest of the crew members, who shift their weight to aid with the steering.

Why do speed skaters wear glasses?

speed-skating

Speed skaters can fly around the ice at upwards of 40 mph, so those sunglasses-type specs they wear aren't merely ornamental. At such high speeds, it's not very pleasant to have wind blowing in your eyes; it's particularly nightmarish if the breeze is drying out your contact lenses. On top of that, there's all sorts of ice and debris flying around on a speed skating track that could send you on a fast trip to the ophthalmologist.

Some skaters also say the glasses help them see the track. American skater Ryan Bedford recently told the Saginaw News that his tinted shades help him focus on the track and filter out distracting lights and camera flashes from the crowd.

What kind of heat are the biathletes packing?

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As you might guess, there are fairly strict rules governing what sort of rifles biathletes carry on the course. They are equipped with guns chambered for .22 LR ammunition. The gun must weigh at least 3.5 kilograms without its magazines and ammunition, and the rifle has to have a bolt action or a straight-pull bolt rather than firing automatically or semi-automatically.

Is a curling stone really made of stone?

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You bet it is, and it's not just any old stone, either. Curling enthusiasts swear by a very specific type of granite called ailsite that is only found on the Scottish island of Ailsa Craig. Ailsite supposedly absorbs less water than other types of stone, so they last longer than their competitors.

Ailsa Craig is now a wildlife sanctuary, so no new ailsite has been quarried since 2002. As a result, curling stones are incredibly expensive. Kays of Scotland, which has made the stones for every Olympics in which curling has been an official event, gets prices upwards of $1,500 per stone.

What about the brooms?

The earliest curling brooms were actual brooms made of wood with straw heads. Modern brooms, though, are a bit more technologically advanced. The handles are usually made of carbon fiber, and the heads can be made of synthetic materials or natural hair from horses or hogs. Synthetic materials tend to be more common now because they pull all of the debris off of the ice and don't drop the occasional stray bristle like a natural hair broom might.

What are the ski jumpers wearing?

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It may look like a ski jumper can pull on any old form-fitting bodysuit and hit the mountain, but things are a bit more complicated than that. Their suits have to be made of a spongy material and can't be thicker than five millimeters. Additionally, the suits must allow a certain amount of air to pass through them; jumpers wearing suits without sufficient air permeability are disqualified. (This rule keeps jumpers from wearing suits that could unfairly act as airfoils.) These rules are seriously enforced, too; Norwegian skier Sigurd Petterson found himself DQed at the 2006 Torino Games due to improper air permeability.

Those aren't the only concerns, though. In 2010, judges disqualified Italian jumper Roberto Dellasega because his suit was too baggy.

What's up with the short track speed skaters' gloves?

Gloves
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If you watch a bit of short track speed skating, the need for gloves quickly becomes apparent. When the skaters go to make passes or careen around a turn, they need the gloves to keep from cutting their hands due to incidental contact with other skaters' blades.

There's more to the gloves than just safety, though. Since the skaters' hands often touch the ice during turns, they need hard fingertip coverings that won't add friction and slow them down. The tips can be made of any material as long as it's hard and smooth, but you've got to give American skater Apolo Ohno some style points for the gold-tipped left glove he broke out in 2010.

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