Earlier today, my wife came over to me, hands clasped, excited to show me her find—a wood frog! It turned out there was more than just one, too. As I looked around the grass, I spotted at least 3 or 4 more. I took a couple pictures, logged it on iNaturalist, and decided it was about time I sat down to write about these frogs which are far more interesting than the name Wood Frog might have you believe.
The Wood Frog is a sort of rusty-tan color with a dark band across the eye like a raccoon, distinguishing itself from all other North American frog species. If you are ever in the woods and see a frog wearing a Zorro mask, it’s a Wood Frog—that or another frog trying to rob someone, but since frogs don’t typically do that sort of thing, the latter isn’t likely.
The Wood Frog has a range extending pretty much diagonally from Alaska, across Canada and the Great Lakes region, down to the Appalachians in the eastern US. In their range, they inhabit forests, favoring wet woodlands, bogs, ravines, and tree-filled swamps. Here, they feed on small invertebrates of the forest floor and other dwellers of the leaf litter. In the springtime, however, Wood Frogs use vernal ponds and ephemeral wetlands for creating the next generation. In the fall, the Wood Frogs begin a migration to upland habitats to overwinter. These winter habitats, or hibernacula, tend to be under the leaf litter or in the upper layers of the soil. That’s where things get interesting.
Like other frogs of the north such as the Gray Tree Frog, the Wood Frog is incredibly cold tolerant. As the frog prepares to go dormant for the winter, urea is accumulated in the body tissues and glycogen from the liver is converted into absurd amounts of glucose. That’s right. Sugar. The Urea and glucose act as an antifreeze, helping to protect the bodies cells by limiting the amount of ice crystals which can form within the body and prevent the shrinkage of cells. This adaptation allows for up to 65% of the frogs body to be completely frozen without issue. During this time, if you were to dig one up, you would almost certainly think it was dead. Or perhaps a piece of wood shaped like a frog. As winter comes to an end and spring begins, the Wood Frog begins to thaw and its heart begins to beat. Their bodies are a little rigid at first, and their movements sluggish, but hey, you would be too if you’d spent the winter as a frozen block.
Their emergence is one of the earliest, along with Spring Peepers, and they quickly begin their chorus. I use the term chorus because that’s what it is called, not because of the beauty of their sound. In fact, their call is most aptly described as if a duck and a chipmunk had a baby that couldn’t stop laughing, or that noisemaker toy that you may of had as a kid that made a weird throaty chuckly sound when you shook it. Honestly, I have no idea how to explain it. Take a listen below.