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♪ Everyone knows this sound.

[rattling] It means danger.

Rattlesnakes inspire fear.

I mean, just look at that face.

But for the most part, they really don't deserve it.

Okay, yeah, a single venomous bite would send you to the hospital, but rattlesnakes really don't want to bite you, which is where the rattle comes in.

It's a polite way to say, "Back the heck off."

So how do they make that sound, that loud buzz you just can't ignore?

It's not just the snake version of a maraca with little bits shaking around inside.

The rattle is actually a bunch of loosely interlocking segments.

Check out the inside.

The segments are made of the same hard protein that your fingernails are made of, called keratin.

You can see how they hook together.

Undulating waves travel down the length of the rattle.

The snake shakes its tail so quickly it just looks like a blur, unless you slow it down.

The segments are all loose and jiggly, so they click against each other.

Rattlesnakes get a new segment every time they shed their skin.

Each new segment grows inside the last one.

So when it sheds, they stay hooked together.

So the older the snake, the longer the rattle, unless it gets broken, which is what usually happens in the wild.

Rattlesnakes can move their tails back and forth 50 to 100 times every second.

It's one of the fastest sustained muscular contractions in nature, right up there with a hummingbird's beating wings.

And rattlesnakes can keep that buzz going nonstop for up to two hours.

But despite that ability, they don't want to rattle at all if they can help it.

Rattlesnakes are ambush predators, so they want to keep a low profile.

To get within striking distance, they need to stay hidden and silent.

Rattling blows their cover, letting anyone in the area know exactly where they are.

So they only use it to scare off their enemies.

And when they slither around, they keep the rattle in silent mode, holding it up in the air to stay quiet.

Yep, this viper that gets all the attention really doesn't want any attention at all.

If you think Deep Look is wild, check out America from Scatch.

It's a show from PBS Digital Studios that asks, "What might the United States be like if it was founded today?"

Like, what if there were no states?

Link is in the description.