Peepers: freeze protection strategies

When the temperature dropped below forty degrees, the frogs shut up. A few hours later, we hit the twenties, the pond was ice and the rocks from which the frogs had called were snow-covered.

The only sound was the creak of a Virginia pine’s knotty entrails, twisted by the weight of ice on its needles and branches. (Like other sounds on this blog, you’ll need to be on the website not the email summary, to hear.)

How do these crazy little frogs survive such temperature swings? Surely they’re all frozen to death by now?

A thermometer inserted just below the crust of snow and ice suggests the peepers’ first strategy. It is ten degrees warmer just an inch under the soil. By creeping into holes, bark crevices, and cracks in rocks the frogs find microclimates that, if not toasty, are more temperate.

2015-03-05 ice snow 010The peepers’ other defense is not so obvious. Their livers gush glucose into the blood, flooding their organs with sugary antifreeze. The bodies of these candied frogs can freeze without damage to their cells. Peepers can move in and out of this sugar-high within hours, making them well-adapted to the ill temper of the spring weather goddesses in eastern North America. After the last ice age, they were one of the first frog species to hop up north.

(For those wondering after my last post how a “spring pepper” might differ from a spring peeper, see here. Apologies for my many typos…)

18 thoughts on “Peepers: freeze protection strategies

  1. James

    Living in peeper land myself (far western NJ), I’ve always wondered how they survive the cold. They definitely haven’t come out here yet. (BTW, that last link is to a pepper grinder. Did I miss a joke?).

  2. pathdoc70

    David, interesting info on the Spring Peepers which I have here in NE Alabama. Funny you should mention the Spring Pepper, I have that too with crushed red pepper in it. 😊
    Mike O’Brien

  3. Minyon Bond

    I’ve tried, and tried again, but cannot shake my image of you popping a peeper into your mouth to actually check that effective percentage of glucose.

  4. batesvillian

    Do I detect a Pythonesque flavor to your description of the peepers’ freeze protection strategies?

    “Lovingly frosted in glucose” indeed.
    Seriously, we’re set to have a record low tonight in Piedmont Virginia (7F) though our peepers have yet to emerge. I expect we’ll hear them by next week, with highs in the 50s and 60s during the day.

  5. april minkler

    We heard them over here (between Monteagle and Tracy City (TN) the other night, and I was apprehensive for them when the temps dropped so precipitously. Glad to know they’ve got this built-in safeguard. Makes me wonder if someone who was inebriated might freeze to death a little slower than someone with no alcohol in their system?

    1. David George Haskell Post author

      Excellent question. Perhaps, but alcohol sends blood to the extremities, so the reverse is likely true. I also think you’d need soooo much alcohol that you’d be poisoned and dead before the antifreeze kicked in. Same for sugars: our bodies could not tolerate the concentrations that these frogs pump into the blood.

  6. Scott

    We’re weeks from hearing peepers here in the northern Piedmont. In fact, we had a peeper walk scheduled for tonight in our natural area preserve, but everything’s buried under a foot of snow, and the breeding puddles are frozen solid.


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