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Learn how some animals have adapted to survive in some of the hottest and driest environments in the world, by covering themselves in mucus and calling it good.

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[Intro]   Add this to my growing list of things I’m really glad humans don’t do.   Imagine if, every time you got a little dehydrated, your body started oozing mucus from every pore … until you were coated with it.   Then your body shut down. And when you finally woke up -- when it rained, or some other source of water came along -- the first thing you’d have to do is fight your way out of a lovely cocoon made of your own boogers.   If that’s what happened to humans, I would take pains to never do anything that would make me even break the tiniest sweat.    But for some animals, that’s the only option if they want to stay alive in a dry spell.   These organisms have adapted to survive in some of the hottest and driest environments in the world, by going dormant in a process called estivation.   It might sound a lot like hibernation, and it is a similar process – the animal’s body is basically shutting down for a while so that it consumes fewer resources.    But when animals hibernate, it’s usually because of lack of food, and it’s typically cold outside. Estivation is different because an animal’s main focus is conserving water, and it’s usually very hot out.   Estivation, just like hibernation, works differently for each animal, depending on its needs, but the basics are the same. Its heart rate slows, it takes in way less oxygen than usual, and it doesn’t consume any food or water.   But water doesn’t usually hang around for long, of course, especially when it’s hot. And, dormant or not, an animal won’t survive if its tissues dry out.   So estivating animals prevent water loss usually by forming a crusty mucus coating.   Case in point: the African lungfish. Which is exactly what it sounds like – a fish with lungs and also gills...but lungs!   Normally, it lives in swamps and marshes, mostly absorbing oxygen with its gills and surfacing a couple of times an hour to breathe air. With its lungs. Even though it’s a fish.   But in drier times, when the swamps turn to mud, it burrows into the mud and oozes out what’s known as a mucus cocoon, leaving an airway open so that it can keep breathing air.    While it’s in there, its body consumes its own muscle tissue for the tiny bit of energy that it needs.    And since it’s not peeing, urea builds up in its system to a concentration about twice of what’s fatal for most other animals.    Then, when it comes out of estivation, the African lungfish has the pee of a lifetime.     Other estivating animals use slightly different techniques.   Dry seasons are hard for frogs, for instance, because they don’t drink water; they absorb it through their skin, so drying out can be especially dangerous.    For the young West African reed frog, surviving a dry spell requires climbing to the highest plant it can find, curling its limbs up into the folds of its skin, covering itself in mucus, and exposing itself to the sun.   Might seem like an odd way to keep from dehydrating, but its skin cells contain iridophores, which reflect light; this helps keep it from absorbing heat from the sun.    Meanwhile, its mucus coating stops most of the water in its body from evaporating.   And finally, we have the Australian water-holding frog which has developed an estivation method so successful that humans have even found a way to exploit it.    The Outback gets less than 30 centimeters of rain a year. So just before the dry season comes, the frog soaks up as much water as it can through its skin. Then, it uses its hind legs to burrow nearly a meter into the mud, where it produces a delightful skin-and-mucus cocoon.    And it can stay in there for years.   When heavy rains start to fall again, a hormone trigger wakes up the frog. It surfaces, emerging from the dried-up skin bag… which it eats for breakfast.    But if you’re ever lost in the Australian outback without water, you can take advantage of your newfound knowledge of estivation – aboriginal people have been doing it for centuries.    Just stomp on the ground as hard as you can until you hear croaking. Dig in that spot, and you’ll catch yourself a water-holding frog. Then, simply place your mouth on the frog’s rear end and squeeze.    Voila! Perfectly drinkable water...type stuff.    If I had the option, I'd rather just coat myself in mucus, I think.   Thanks for watching this SciShow Dose, and thanks especially to our latest President of Space, Tab for a Cause, which lets you raise money for a charity every time you open a new tab in your browser. Visit to learn more.   And don’t forget to also  go to and subscribe!