January 2020: Frozen Frogs
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The gray tree frog can change colors from dark gray to light gray to a bright green.

Our own local wonder – the wood frog (Lithobates sylvaticus) and the gray tree frog (Hyla versicolor) can freeze in winter.

Once an ice crystal makes contact with one of these frogs while in brumation (like hibernation but for reptiles and amphibians), it triggers a cascading formation of ice particles. The frog’s liver converts stored glycogen into glucose. This sugar is carried through the bloodstream to all the tissues to prevent desiccation of the frog. As much as seventy percent of the water in the frog can freeze into ice without the frog dying. The heart stops. All organs cease functioning. The amphibian appears dead. And it undergoes cycles of freezing and thawing all winter as the temperatures fluctuate.


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The wood frog is an early riser, sometimes appearing in ponds as soon as February.

As spring nears, reanimation occurs. The frogs thaw and though sluggish at first and a little worn, their bodies work hard at cell repair from any winter damage. It isn’t long before they raise their voices in joyous mating calls, a cacophony of sound among the still cold wetlands that says, “Life, Life, Life is here.”