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When Hank watches nature documentaries he always comes away with one big question: how is that not killing you? In today's episode of SciShow he looks at three unusual ways that animals manage not to get killed by nature.

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Hank Green: Have you ever watched a nature show and come away feeling like a little bit of a wuss, I mean, these animals, here they are doing their thing, swimming in crazy cold water, pounding their heads against trees, like getting smacked in the face by deadly snakes, and like, you're thinking, I cry when I get stung by a bee, complain about caffeine headaches, how is that not killing you?

[SciShow intro]

Well, let's look at three unusual ways that animals manage not to get killed by nature. 1) How are you not freezing to death? The ocean around Antarctica is super cold, like, below freezing cold, yes, because the water is so salty it can stay liquid a few degrees below zero Celsius. But even though seawater has a lower freezing point, it is still full of floating ice particles and if a fish swallows one, since they're cold blooded, it can kick off a deadly internal freezing process. So how do fish survive without turning into fish-cubes? Well, just like our cars run when it's below zero, they use antifreeze! Except they manufacture it themselves inside of their bodies. Certain fish species, like this icefish, produce antifreeze proteins, or AFPs, that attach to crystals that show up in their blood. By binding to these crystals, these proteins basically lower the freezing point even more, further reducing the temperature required for the ice to grow by about 2.2 degrees Celsius, 2 degrees less than it would take for a fish's blood plasma to freeze. Some cold climate insects, like the snow flea, produce AFPs that are structurally different from those found in fish, indicating that animal antifreeze is a product of convergent evolution. Now if only my car could start making its own.

2) How are you not getting brain damage? Woodpeckers can bang their faces against solid objects up to 12,000 times a day at an average of 20 times per second, with deceleration forces of 1200 G's. By comparison, humans may lose consciousness at just under 5G's, and so, why don't woodpeckers have messy mushballs for brains? Well, for one, they've got built in shock absorbers, the bone that encompasses their brain is spongy and thick and laced with lattice-like trabeculae, bits of tissue that act like a protective mesh. They've also got their tongues. Woodpecker tongues wrap all the way around the skull, going up the back and over the top, fitting snugly into one end of the Hyoid bone. This weird wishbone shaped bone also does a wrap around the skull, and together, it and the tongue help absorb the shock of the head-banging, so the bird doesn't shake its brains loose. But that's not even all of it! They also have super powered eyelids. Just before a woodpecker's beak strikes wood, their thick nictitating membranes, or like second set of eyelids, slide into place to keep the eyes from popping right out of their skull on impact, kind of terrible to think about, but useful.

3) How is that cobra not killing you? By now, we've probably all seen Randall's infamous video narration of that nasty honey badger raising cane on neighborhood cobras without getting killed, so why doesn't a cobra strike to the face kill these guys? Well, we're not actually sure, but we do know what's going on with its fellow snake-slaying friend, the mongoose. As you may recall from our episode on venomous animals, snake venoms work in a couple of different ways. Cobras use neurotoxins, which work by binding to the victims' acetylcholine receptors, wreaking havoc on the nervous system. But the mongoose can produce a special sugar chain that links to these receptors preventing the snake's neurotoxins from binding to them, so basically, the sugars on these receptors just bounce the venom molecules away, enabling the animal to get all Rikki-Tikki-Tavi. So there you have it, some animals are just really good at not dying.

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