WEBVTT - Why Don't Penguin Feet Freeze?

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<v Speaker 1>Welcome to brain stuff from how stuff works. Hey, brain stuff,

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<v Speaker 1>Lauren Vogel bomb here. How long could you stand on

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<v Speaker 1>Antarctic ice before your bare feet froze solid? A minute?

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<v Speaker 1>Maybe two? If you're an emperor penguin, you can do

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<v Speaker 1>it for two months, and in wind chills as low

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<v Speaker 1>as negative seventy five degrees fahrenheit that's about negative sixty

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<v Speaker 1>degrees celsius. Those naked bird feet may look positively frigid,

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<v Speaker 1>but their special circulation acts as a kind of anti

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<v Speaker 1>freeze to keep them just warm enough in environments where

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<v Speaker 1>we would get frost bite immediately. Penguins are adapted just

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<v Speaker 1>for cold temperatures. They have specialized super insulating feathers that

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<v Speaker 1>keep heat in. We humans would get frost bite in

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<v Speaker 1>penguins place, specifically because our bodies are adapted to a

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<v Speaker 1>wider range of temperatures. To keep our internal body temperature

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<v Speaker 1>right around in ninety eight degrees. In the heat and

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<v Speaker 1>the cold, the blood vessels inner skin expand or contract

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<v Speaker 1>to direct or restrict the flow of blood out to

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<v Speaker 1>our skin. Our organs stopped working. Some were above a

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<v Speaker 1>hundred and four degrees fahrenheit that's about forty degrees celsius.

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<v Speaker 1>So when we get warm, our blood vessels dilate to

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<v Speaker 1>circulate more warm blood to the skin, where hopefully that

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<v Speaker 1>heat transfers out into the environment. A sweating can help

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<v Speaker 1>with this, but our organs also stop working somewhere below

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<v Speaker 1>ninety degrees fahrenheit that's about thirty two degrees celsius. So

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<v Speaker 1>when we get cold, most of our blood vessels constrict

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<v Speaker 1>to limit the amount of warm blood going too the

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<v Speaker 1>skin where it would lose more heat, and thus keep

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<v Speaker 1>that warmth circulating in our core areas. Our hands, feet,

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<v Speaker 1>and limbs in particular are full of these tiny blood

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<v Speaker 1>vessels that can either warm up or chill off fast.

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<v Speaker 1>Your hands may even appear paler during exposure to freezing

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<v Speaker 1>weather because there's less blood in them. It's been redirected

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<v Speaker 1>to the core of your body to make sure those

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<v Speaker 1>vital organs stay warm. But penguin legs and feet have

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<v Speaker 1>evolved specifically to lose as little heat as possible. Penguin

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<v Speaker 1>feet hold onto heat by restricting blood flow in really

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<v Speaker 1>cold weather, keeping foot temperature just above freezing. Penguin legs

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<v Speaker 1>work like a heat ex change system. Blood vessels to

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<v Speaker 1>and from the feet are very narrow and woven closely together,

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<v Speaker 1>cooling the blood from the body on the way to

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<v Speaker 1>the feet and heating the blood as it returns to

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<v Speaker 1>the body. Feet get cool blood, so there's less heat

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<v Speaker 1>to lose while the body stays toasty. This special ability

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<v Speaker 1>is part of how penguins keep their eggs warm until

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<v Speaker 1>they hatch. Male emperor penguins incubate a single egg on

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<v Speaker 1>top of their feet for two months in the dark

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<v Speaker 1>of winter while females are out feeding at sea. They

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<v Speaker 1>also cover the egg with a flap of warm belly

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<v Speaker 1>skin called a brood pouch to keep it out of

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<v Speaker 1>the elements, and nurturing doesn't stop there for these dedicated dads.

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<v Speaker 1>If females haven't returned with food by the time the

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<v Speaker 1>chicks hatch, male emperors feed their babies for a few

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<v Speaker 1>days on a kind of milk made from special cells

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<v Speaker 1>inside their throats. Today's episode was written by Lori and

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<v Speaker 1>Fick and produced by Tyler Clang for iHeart Media and

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<v Speaker 1>How Stuff Works. To learn more about this and lots

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<v Speaker 1>of other core topics, visit our home planet, how stuff

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