BrainStuff Classics: How Do Cold-Blooded Animals Survive the Winter?

Reptiles and amphibians have all sorts of adaptations for surviving cold weather, even in places where temperatures dip below freezing. Learn how they manage the cold in this classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio.

Speaker 2 (00:06):
Hey brain Stuff, Lauren Vogel Bomb here with a classic
episode from our archives. But with the weather turning colder
here in the Northern Hemisphere, I was thinking about all
of the cold blooded critters out there that depend on
sunlight and warm temperatures to keep their bodies going. Here
are some of the ways that they survive the winter.

Speaker 1 (00:28):
Hey brain Stuff, I'm Lauren Vogelbomb, and you and I
can complain about seasonal chills all we want, but at
the end of the day, we're basically walking furnaces. Humans
are endotherms, meaning that our bodies produce heat internally. We're
also able to maintain a body temperature that stays more
or less constant, so we should count our blessings. Not
all animals have these physiological advantages. Apart from a handful

(00:50):
of species like the monstrously big leather back sea turtle,
very few reptiles or amphibians are able to keep their
bodies at a constant temperature, and since they can't warm
themselves up, these creatures must extract heat from their environment.
But what happens when that environment gets colder? Out of
frogs snakes and turtles make it through the winter months
in places that see blankets of snow, ice over lakes,

(01:11):
and sub freezing temperatures year after year. A lot of
reptiles and amphibians undergo periods of extreme seasonal inactivity. When
the weather gets colder. They may experience decreased heart rates,
slowed metabolisms, and lower overall body temperatures. Scientists disagree over
what to call this state. Everyone accepts that it's some
kind of dormancy, but while some experts classify it as hibernation,

(01:33):
others refer to it as brumation. Dormant snakes generally hold
themselves up in winter dens. These shelters may take the
form of an abandoned rodent burrow, an exposed crevice on
a rock face, or some naturally occurring hole underneath a tree.
Various snakes have also been known to turn household basements
or garages into winter lodges in seasonally cold areas like

(01:54):
Canada and the northern United States. Snakes must choose their
dens with care. Ideally, a winter hangout spot will descend
below the local frost line, the maximum depth beneath the
ground at which soil freezes. Hiding out underground is the
survival strategy of choice for lots of tortoises and turtles
as well. Some species, such as the gopher tortoise, dig
their own burrows, but it's not uncommon to find to

(02:15):
the shelled reptiles occupying pre dug unoccupied rodent holes. Now
a hibernating black bear can sleep for more than one
hundred days straight without consuming any food or water. Reptiles
tend to be more active during hibernation or breamation. When
a midwinter warm spell comes along, they'll use it as
an opportunity to crawl up to the surface, bask in
the sunlight for a little while, and maybe grab a

(02:37):
quick drink. Reptiles are perceived as loners, a reputation that
isn't entirely deserved. Consider the Eastern diamondback rattler, who doesn't
seem to mind collaborating with gopher tortoises. Members of both
species will sometimes go dormant together inside the same burrow. Likewise,
snakes often share their dens with other snakes. Garter snakes
are famous for hibernating in huge groups that may consist

(02:59):
of hundreds or even thousands of individuals. One Canadian den
reportedly contained no fewer than eight thousand snakes. Indiana Jones
and other videophiles will want to keep their distance as
snakes go. Garters are remarkably cold tolerant. One species can
even survive the unbelievable experience of having forty percent of
the liquid water inside its body freeze solid, but only

(03:21):
if it's allowed to thaw out after a few hours.
But the wood frog takes freeze tolerance to a whole
new level. A North American native, this cold weather warrior
has the distinction of being the only amphibian in the
Western hemisphere whose range extends into the Arctic Circle. Every autumn,
wood frogs bury themselves under a thin blanket of leaf
litter on the forest floor. There they will remain dormant

(03:43):
for up to eight months. In the process, the heart
temporarily stops beating and the frogs enter a state of
suspended animation. Left to the mercy of the elements. The
amphibians freeze at temperate and polar latitudes. Fortunately, the liver
pumps loads of glucose into the bloodstream, while urine is
retained than the body. All that helps keep the cells
from drying out, which is what would normally happen during

(04:05):
the freezing process. Therefore, a full sixty five percent of
all the water in a wood frog's body can become
frozen and the amphibian will still live to rib it
another day. Moreover, the frog may be kept frozen at
negative eighteen degrees celsius or about zero degrees fahrenheit, for
as long as two hundred and eighteen days. Another example

(04:26):
of this cool survival strategy can be found in far
North Russia. The Siberian salamander lives in areas that get
temperatures of negative fifty degrees celsius that's negative fifty eight
fahrenheit or lower. To stay alive, it hibernates underneath logs, vegetation,
and snowbanks. A compound in their bloodstream keeps the critters
alive when the majority of its body water turns to ice.

(04:47):
Terrestrial amphibians with poor digging skills, like the wood frog,
tend to either hibernate in pre existing burrows or fine
shelter at ground level. Good burrowers, such as the American
toad and spotted salamander, proactive dig winter holes from themselves
that extend below the frost line. For aquatically inclined amphibians,
there's another option. Bullfrogs are lake and pond denizens who

(05:09):
find oxygen rich bodies of water and spend their winters
imprisoned under the surface of ice that forms there. Painted
turtles employ a similar strategy. Reptiles generally use their lungs
to breathe, but some semi aquatic turtles can also absorb
water born oxygen through their skin overwintering. Painted turtles do
this extremely well, Plus they can lower their metabolic rates

(05:30):
to the tune of ninety five to ninety nine percent
each winter. That's how they stay alive beneath thick sheets
of lake ice for months on end. Sometimes you can
even see them swimming around under the frozen barriers. But
why go through the hassle of skin breathing when you
can turn your snout into a snarkel. In January of
twenty eighteen, the Internet was greatly amused by some North

(05:51):
Carolina alligators whose noses were seen poking up out of
a frozen pond. Gators can't survive being trapped in icy
water for much longer than a week or so. For
long term winter lodgings, they construct deep burrows out of
waterside mud. Today's episode is based on the article Weird
Ways Reptiles and Amphibians Survived the Winter on HowStuffWorks dot Com,

(06:15):
written by Mark Mancini.

Speaker 2 (06:17):
A brain Stuff is production of ihart Radio in partnership
with how stuffworks dot Com, and it's produced by Tyler Klang.
Four more podcasts from my heart Radio, visit the iHeartRadio app,
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