Iced In, a Story of the Wood Frog

by Meredith Naughton

He started this year off like he has every other—frozen solid. While people may dress in layers of wool and down to deter the chill, the wood frog simply lets the cold in. Sitting on the ground or tucked under the leaves, the wood frog spends each winter motionless, his body frozen through with ice. Each spring he thaws and leaps into the woods towards another season of life.

It’s November in the Richmond Town Forest, and like many of us, this frog is getting ready for winter. In contrast to the sleep-like hibernation of many animals, the wood frog’s winter routine is much more bizarre. It happens quickly, as if a spell is cast and the freeze crackles across his back, catching him between hops. Remarkably, he’s still alive. Perhaps it’s the bandit mask over his eyes that grants this Richmond resident such rule-bending biological mischief, or perhaps it’s the ice-inducing agents in the wood frog’s skin. Triggered by the cold, these specialized cellular particles activate the spread of ice throughout the water under the skin and between the organs, leaving him stiff and cold.

Like a full bottle in the freezer, living cells usually burst when frozen. But the wood frog dodges that deadly eruption. Sugars produced by his liver are pumped into every cell, and his blood forms to the consistency of a thick grape jelly.  His heart doesn’t beat, but inside his frozen shell the wood frog’s cells remain supple.

Spring arrives, and the frog thaws. He is on a mission: to mate and lay eggs as quickly as possible. He hops directly into the party of the year: the annual amphibian breeding bender. This is no polite spring gathering of estranged neighbors after a long winter. The wood frogs are frenzied; their breeding grounds are seasonal waters. More than a puddle but not quite a pond, vernal pools fill up for only part of the year and host frogs and salamanders as they wake from winter. Throughout the Richmond Town Forest, and from Maryland to the Arctic Circle (they are the only amphibian that can survive that far north), wood frogs assemble in the small forested pools of water to distribute their genes.

The male wood frog also has one complication: he cannot tell apart males from females. In fits of splashes and croaks, the male wood frog squeezes each frog he encounters. If they’re not fat enough to be a female, he releases and hugs their neighbor. After this immodest trial and error is complete, adult wood frogs forget about each other and their thousands of new babies. They spend the summer and fall eating insects alone and lounging near the shady pools of water.

Since rounding the corner from early to late fall, the wood frog has finished his lounging for the year. Snow has descended on the Richmond town forest. If he hasn’t already, one day soon the wood frog will cease hopping for the year.