WEBVTT - How Do Cold-Blooded Animals Survive the Winter?

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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>I'm Lauren folk Bomb, and you and I can complain

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<v Speaker 1>about seasonal chills all we want, but at the end

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<v Speaker 1>of the day, we're basically walking furnaces. Humans are endotherms,

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<v Speaker 1>meaning that our bodies produce heat internally. We're also able

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<v Speaker 1>to maintain a body temperature that stays more or less constant,

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<v Speaker 1>so we should count our blessings. Not all animals have

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<v Speaker 1>these physiological advantages. Apart from a handful of species like

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<v Speaker 1>the monstrously big leather back sea turtle, very few reptiles

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<v Speaker 1>or amphibians are able to keep their bodies at a

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<v Speaker 1>constant temperature, and since they can't warm themselves up, these

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<v Speaker 1>creatures must extract heat from their environment. But what happens

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<v Speaker 1>when that environment gets colder? How to frogs, snakes, and

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<v Speaker 1>turtles make it through the winter months in places that

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<v Speaker 1>see blankets of snow, iced over lakes and subfreezing temperatures

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<v Speaker 1>year after year. A lot of reptiles and amphibians undergo

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<v Speaker 1>periods of extreme seasonal inactivity. When the weather gets colder.

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<v Speaker 1>They may experience decreased heart rates, slowed metabolisms, and lower

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<v Speaker 1>overall body temperatures. Scientists disagree over what to call this state.

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<v Speaker 1>Everyone accepts that it's some kind of dormancy, but while

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<v Speaker 1>some experts classify it as hibernation, others referred to it

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<v Speaker 1>as brumation. Dormant snakes generally hold themselves up in winter dens.

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<v Speaker 1>These shelters may take the form of an abandoned rodent burrow,

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<v Speaker 1>an exposed crevice on a rock face, or some naturally

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<v Speaker 1>occurring hole underneath a tree. Various snakes have also been

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<v Speaker 1>known to turnhousehold basements or garages into winter lodges in

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<v Speaker 1>seasonally cold areas like Canada and the northern United States.

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<v Speaker 1>Snakes must choose their dens with care. Ideally, a winter

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<v Speaker 1>hangout spot will descend below the local frost line, the

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<v Speaker 1>maximum depth beneath the ground at which soil freezes. Hiding

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<v Speaker 1>out underground is the survival strategy of choice for lots

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<v Speaker 1>of tortoises and turtles as well. Some species, such as

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<v Speaker 1>the gopher tortoise, dig their own burrows, but it's not

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<v Speaker 1>uncommon to find the shelled reptiles occupying pre dug unoccupied

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<v Speaker 1>rodent holes. Now, a hibernating lack bear can sleep for

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<v Speaker 1>more than one hundred days straight without consuming any food

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<v Speaker 1>or water. Reptiles tend to be more active during hybernation

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<v Speaker 1>or romation. When a midwinter warm spell comes along, they'll

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<v Speaker 1>use it as an opportunity to crawl up to the surface,

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<v Speaker 1>bask in the sunlight for a little while, and maybe

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<v Speaker 1>grab a quick drink. Reptiles are perceived as loaners, a

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<v Speaker 1>reputation that isn't entirely deserved. Consider the Eastern diamond back rattler,

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<v Speaker 1>who doesn't seem to mind collaborating with gopher tortoises. Members

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<v Speaker 1>of both species will sometimes go dormant together inside the

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<v Speaker 1>same burrow. Likewise, snakes often share their dens with other snakes.

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<v Speaker 1>Garter snakes are famous for hibernating in huge groups that

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<v Speaker 1>may consist of hundreds or even thousands of individuals. One

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<v Speaker 1>Canadian den reportedly contained no fewer than eight thousand snakes.

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<v Speaker 1>Indiana Jones and other videophiles will want to keep their

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<v Speaker 1>distance as snakes go. Garters are remarkably cold tolerant. One

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<v Speaker 1>species can even survive the unbelievable experience of having of

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<v Speaker 1>the liquid water inside its body freeze solid, but only

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<v Speaker 1>if it's allowed to thaw out after a few hours,

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<v Speaker 1>but the wood frog takes freeze tolerance to a whole

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<v Speaker 1>new level. A North American native, this cold weather warrior

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<v Speaker 1>has the distinction of being the only amphibian in the

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<v Speaker 1>Western hemisphere whose range extends into the Arctic Circle. Every autumn,

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<v Speaker 1>wood frogs bury themselves under a thin blanket of leaf

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<v Speaker 1>litter on the forest floor. There they will remain dormant

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<v Speaker 1>for up to eight months. In the process, the heart

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<v Speaker 1>temporarily stops beating and the frogs enter a state of

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<v Speaker 1>suspended animation. Left to the mercy of the elements, the

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<v Speaker 1>amphibians freeze at temperate and polar latitudes. Fortunately, the liver

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<v Speaker 1>pumps loads of glucose into the bloodstream, while urine is

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<v Speaker 1>retained within the body. All that helps keep the cells

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<v Speaker 1>from drying out, which is what would normally happen during

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<v Speaker 1>the freezing process. Therefore, a full six of all the

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<v Speaker 1>water in a wood frog's body can become frozen, and

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<v Speaker 1>the amphibian will still live to rib it another day. Moreover,

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<v Speaker 1>the frog may be kept frozen at negative eighteen degrees

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<v Speaker 1>celsius or about zero degrees fahrenheit, for as long as

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<v Speaker 1>two hundred and eighteen days. Another example of this cool

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<v Speaker 1>survival strategy can be found in far North Russia. The

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<v Speaker 1>Siberian salamander lives in areas that get temperatures of negative

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<v Speaker 1>fifty degrees celsius that's negative fifty eight fahrenheit or lower.

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<v Speaker 1>To stay alive, it hibernates underneath logs, vegetation, and snow banks.

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<v Speaker 1>A compound in their bloodstream keeps the critters alive when

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<v Speaker 1>the majority of its body water turns to ice. Terrestrial

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<v Speaker 1>amphibians with poor digging skills, like the wood frog, tend

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<v Speaker 1>to either hibernate in pre existing burrows or fine shelter

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<v Speaker 1>at ground level. Good burrowers, such as the American toad

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<v Speaker 1>and spotted salamander, proactively dig winter holes from themselves that

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<v Speaker 1>extend below the frost line. For aquatically inclined amphibians, there's

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<v Speaker 1>another option. Bullfrogs are lake and pond denizens who find

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<v Speaker 1>oxygen rich bodies of water and spend their winters imprisoned

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<v Speaker 1>under the surface of ice that forms there. Painted turtles

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<v Speaker 1>employ a similar strategy. Reptiles generally use their lungs to breathe,

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<v Speaker 1>but some semi aquatic turtles can also absorb waterborne oxygen

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<v Speaker 1>through their skin over wintering. Painted turtles do this extremely well,

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<v Speaker 1>Plus they can lower their metabolic rates to the tune

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<v Speaker 1>of each winter. That's how they stay alive with the

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<v Speaker 1>thick sheets of lake ice for months on end. Sometimes

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<v Speaker 1>you can even see them swimming around under the frozen barriers.

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<v Speaker 1>But why go through the hassle of skin breathing when

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<v Speaker 1>you can turn your snout into a snarkle. In January,

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<v Speaker 1>the Internet was greatly amused by some North Carolina alligators

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<v Speaker 1>whose noses were seen poking up out of a frozen pond.

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<v Speaker 1>Gators can't survive being trapped in icy water for much

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<v Speaker 1>longer than a week or so. For long term winter lodgings,

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<v Speaker 1>they construct deep burrows out of waterside mud. Today's episode

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<v Speaker 1>was written by Mark Nancini and produced by Tyler Clang.

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<v Speaker 1>For more on this and lots of other warm topics,

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<v Speaker 1>visit our home planet, how Stuff Works dot com