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Uploaded:2016-07-23
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How do they do it? Penguins standing on ice, not only for days, but their whole lives! And their feet don’t hurt like ours would. It has something to do with blood and an amazing twist that penguins have developed.

Hosted by: Hank Green
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Sources:
https://seaworld.org/en/animal-info/animal-infobooks/penguin/physical-characteristics
http://www.independent.co.uk/environment/nature/by-the-left-quick-march-the-emperor-penguins-migration-1212420.html
http://www.coolantarctica.com/Antarctica%20fact%20file/science/cold_penguins.php
http://www.theanswerbank.co.uk/Animals-and-Nature/article/why-dont-penguins-feet-freeze/
https://www.youtube.com/watch?v=3tqjITi8S8s
http://minerva.union.edu/linthicw/concurrent.htm
http://www.biology-pages.info/H/HeatTransport.html
http://shima-miabadi.com/ECOPHYSIOLOGICAL-ARCHITECTURE
http://www.arkive.org/emperor-penguin/aptenodytes-forsteri/image-G53700.html

Images:
countercurrent heat exchange: https://en.wikipedia.org/wiki/File:Countercurrent_exchange.png
Penguin Feet: https://www.flickr.com/photos/cmichel67/16739668936
Adelie Penguins: https://www.flickr.com/photos/10004136@N05/3212303306
Penguins lifting feet: https://www.flickr.com/photos/elisfanclub/5955799837
Antarctica: https://www.flickr.com/photos/61172192@N00/5884680232
Antarctica 2: https://commons.wikimedia.org/wiki/File:Antarctica_(7),_Laubeuf_Fjord,_Webb_Island.JPG
Penguin Swimming: https://commons.wikimedia.org/wiki/File:Gentoo_Penguin_Swimming.jpg
[SciShow intro plays]

Hank: It's like really really cold in Antarctica, it can get way below negative 30 degrees Celsius, plus everything is covered in ice and snow, so how about taking a hike across it barefoot? That is a day in the life of a penguin. In fact, the whole life in the life of a penguin and yet somehow, their feet don't get hurt, or freeze. The trick is they have special adaptations to keep the blood in their feet just barely above zero degrees Celsius while keeping the rest of their tissues nice and warm.

Antarctic penguins keep their bodies warm with thick layers of fat and downy feathers, but their feet are designed for swimming and walking on slippery ice. They're webbed with lots of surface area and no feathers, so it's really easy for them to lose heat, but penguins have a couple of tricks to keep their feet safe in a cold: First the muscles that control their feet are tucked up in their warm body for protection and are controlled by strong tendons to the feet bones kind of like a foot puppeteer.

Not to mention penguin feet are tough. They're mostly made of bone and keratin, the same protein as our fingernails, and when it gets really cold, some penguins will lean back onto their heels and curl their toes to keep them off the frozen ground, but the real secret is, penguins keep their feet just above freezing temperatures using something called counter-current heat exchange.

At the top of each foot a Penguin's blood vessels wrap around each other, so different temperatures of blood are flowing in opposite directions, or counter current this allows heat to transfer from the warm blood entering the feet to the cold blood headed back to the central body. So by the time the blood gets down to the feet with all the oxygen for the cells, most of the heat has already been carried back up, to keep those important muscles and organs warm.

This way the Penguin's feet stay just warm enough to keep them from freezing, and they're not wasting a bunch of energy trying to heat up their feet to body temperature. Humans actually use counter current heat exchange too, although our blood vessels don't actually wrap around each other. This means that on a cold day the blood going to your fingers and toes is actually a little cooler to save a little heat and keep their central body warm.

But our skin, of course, isn't as tough as penguin feet so your fingers and toes can get damaged by the cold much more easily. So even for the Daredevils among us, I would not recommend any barefoot trecks across Antarctica.

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