How Arctic Frogs Survive Being Frozen Alive

When you think about hardy arctic creatures bracing for a cold winter, you’re probably thinking of something huge and furry and possibly antlered. Odds are you’re not thinking of … wood frogs. 

But it may be time to cast that amphibian prejudice aside in light of a new study in The Journal of Experimental Biology that examines the astounding ability of Rana sylvatica to freeze—and live through it. R. sylvatica is a species of wood frog with a range that stretches from the state of Georgia all the way through Canada and into the Arctic Circle.

The study was led by Jon Costanzo of the Department of Zoology at Miami University in Ohio. Costanzo’s research interest in wood frogs goes back 25 years, to when he first learned of their extreme freeze tolerance. (Read about an octopus that survives in extremely cold temperatures.)

“I wanted to understand how the frog could do that on a physiological and chemical level,” he said.

Deep-Frozen Frogs

There are a number of creatures, from reptiles and insects to marine life, that possess some level of freeze tolerance, but few can perform the trick quite like Rana sylvatica. The tiny amphibians can survive for weeks with an incredible two-thirds of their body water completely frozen—to the point where they are essentially solid frogsicles. (Related: “Antifreeze-Like Blood Lets Frogs Freeze and Thaw With Winter’s Whims.”)

Even more incredible is the fact that the wood frogs stop breathing and their hearts stop beating entirely for days to weeks at a time. In fact, during its period of frozen winter hibernation, the frogs’ physical processes—from metabolic activity to waste production—grind to a near halt. What’s more, the frogs are likely to endure multiple freeze/thaw episodes over the course of a winter.

To test the freeze tolerance of Alaskan populations of Rana sylvatica specifically, the researchers compared them with frogs of the same species taken from the local Ohio population. While both exhibited impressive freeze tolerance, there were some obvious differences as well. While the Ohioan wood frogs could be frozen at -4 degrees Celsius (24.8 degrees Fahrenheit) and revived, the Alaskan wood frog was frozen at temperatures as low as -16 degrees Celsius (3.2 degrees Fahrenheit) before being thawed out and returning to its normal healthy state.

And Costanzo is convinced that the small but sturdy amphibians can survive even colder temperatures.

Avoiding Death

The way wood frogs avoid freezing to death is due to so-called cryoprotectants—solutes that lower the freezing temperature of the animal’s tissues. These include glucose (blood sugar) and urea and have been found in much higher concentrations in the Alaskan wood frogs than in their southern counterparts.

Increased levels of cryoprotectants help the frogs’ cells survive. In most animals, prolonged exposure to subzero temperatures causes cellular shrinkage—a process in which the formation of ice in the tissues pulls water from the body’s cells, essentially sucking them dry and eventually killing the cell.  (Related: “Champions of the Cold.”)

But cryoprotectants help the cells resist that shrinkage.

“The solutes tend to depress the freezing point [of tissue],” said Costanzo. “It limits the amount of ice that actually forms in the body at any part. The more of that cryoprotective solute you can accumulate, the less ice will form and therefore the less stress there is on cells and tissues.”

Costanzo and his team also detected the presence of an additional mystery solute in the northern wood frogs, not shared by the local Ohio frogs, and are planning future research to determine its exact nature.

Applications for Medicine

Beyond being fascinating science, the ability to freeze and unfreeze living organs and tissues without damaging them has potentially profound implications for areas such as organ transplantation.

“There’s an obvious parallel between what these frogs are doing to preserve all of their tissues simultaneously and our need to be able to cryopreserve human organs for tissue-matching purposes,” said Costanzo, noting that attempts to successfully freeze human organs for transplants have so far proved unsuccessful, perhaps due to their relative size and cellular complexity.

“If you could freeze human organs even for a short period of time, that would be a major breakthrough because then these organs could be shipped around the world, which would greatly [improve] the donor-matching process,” noted Costanzo.

And that, ironically, is a heartwarming thought.

Follow Stefan Sirucek on Twitter.


Stefan Sirucek is a writer and journalist who reports from both sides of the Atlantic. He's written for the Huffington Post and Wall Street Journal. Follow him on Twitter at @sirstefan.
  • Adeel Hasan

    i belive its crhoprotectants fluid in them, which lowers the freezing point.. How about these frog when the sunny season start, they may have different mechanism for this, when the begin to rise how fluid get cold, how they accomplished homeostasis..

    And my main point is about their heart beat activity,how thier heat acticity is reduced or stopped for a days, have u study or researched about the harmones that reduces or stop activity for days.. And what chemical that again starts heart activity..

    Looking forwad to your reply..
    At my email..

  • Alex

    Enabling long-distance space travel could be killer app.

  • Alex

    Trying consanguinous experiments with a frog that is not freeze-tolerant could also be interesting to see if the cryoprotectants are transferrable (via blood)

  • Orbitcoin

    This is great news for Orbitcoin and space colinization.

    We was planning to research moss as that can come back to life after 1000’s of years, guess a combination of the properties of moss and the properties the Arctic wood frog, Could be massive for cryogenics.


  • joseph

    this is great! how about a whole human body eh would it work on humans alive wahahha

  • roel cagoco

    how about the genetic formation of this wood frog,are there any similar genetic formation to human?try to find out

  • stay curious

    amazing…I wonder what happens to the brain, like can it stop like the other organs or drift into a hybernation.

  • joson joy

    if we are able to determine the mystery solute it will be a great breakthrough.how about sythesising the solute,how it help humans? PLEASE I NEED A REPLY

  • Steve Novotny

    Joseph and space enthusiasts! This would not work on the human body because we need to maintain a specific temperature to be healthy (98.7) even if we had a lower freezing point we would be long dead before we were frozen. Frogs are cold blooded wich means that their temperature as a whole changes with the enviornment. We are warm blooded witch means that we maintain our own temperature unless we are sick.

  • chris c

    Costanzo talking about cell shrinkage in the cold….that’s one letter off from being a Seinfeld episode

  • Jon

    in order for this frog to survive these severe temperatures the frog had to make it so that its body so that the tissue can survive the freezing cold.

  • Teauna Gainwell

    In this article it’s saying that these frogs only come to life once they have un thowed and that they are known to be a antifreeze and they only survive through cold weather. wood frogs stop breathing and their hearts stop beating entirely for days to weeks at a time.

  • Alexis morris

    It’s amazing how the frogs freeze and unfreeze without dying when they completing stop breathing

  • alexis k

    When it freezes it pulls the cells and soaks up the water and kills the cell and it adopits in the tree so it can survive and when it freezes when it freezes it doesent. Breath at all

  • Laverga D’tu Papa

    I need cryoprotestants for mi Legomaiego. Please give me Juan

  • thomas gregg

    Cheek out the BLUE DIAMONDS On clash of clans were a international clan

  • mike d

    What is with these comments????

  • Joe DiSantis

    It is absolutely amazing that this species heart can stop for weeks at a time.What a marvelous specimen to study in so many ways in terms of advancing human breakthroughs.Perhaps preserving organs even temporarily for medical reasons to inject or explore tissue experimentation could someday be possible.Just knowing the pysiology of these creatures offers such huge potential scientific treasures for mankind.

  • Yyr hgf

    There are some super retarded posts on this thread.

  • Laiba Hasan

    Are they warm blooded or cold blooded?

  • Welmuhz Taehyung

    If this frog species can stop their hearth beat , how do they go back to life if the sun is 109 times larger than earth and the apple your aunty told you to buy is 10 as the 10 is equal to 5 to times.

  • Welmugz Taehyung

    i just spelled my name wrong on my first comment :O

  • taylor philips

    what exactly is the chromosome affected in the lithobates sylvaticus or wood frog

  • Dakota Dukes

    What is the affected or deleted chromosome to make this frog do this.
    And is it man made or a natural effect through mutation

  • kyleen wiloughby

    idk anything about this even after reading this


    See the BBC’s Show “Natures Weirdest Events”, Series 2, Episode 3 to see how they can survive and come back to life.
    Its Amazing!

  • James Lott

    Being able to ship organs around the world isn’t the only application for this kind of biology and technology. First thing that popped in my head is sending humans to other planets considering the fact that faster-than-light is probably never going to happen.

  • kate elliot

    Fascinating article. Thank you for sharing it.

  • Fatih Güneş

    I wonder what happens to this animals lifetime. When compared to another animal of the same specie which has never frozen, does it live longer or just the same?

  • Anushka

    Can human also behave like wood frog by inserting cryoprotectants in blood vessels of humans?

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