Wood Frogs: Forest Friends With a Secret Power!

Hello, Geek Parents! If you’ve hiked in the forests of northern North America, chances are you’ve seen a wood frog on your travels. Or, maybe you haven’t. They are one of the most common frogs in the area, but they are also very well camouflaged, as you can see from the photo above. The only way I knew this frog was there was because it hopped. These frogs are everywhere. But just because an animal is common doesn’t mean it’s not special. This forest friend has a secret power.

Wood frogs are indigenous to North America, especially in the northern parts of the continent. They are amphibians, which means they can live on land and water. Their smooth skin is generally brown or tan, but they can also be gray, green, and even shades of red. Unlike birds, where the male is generally more brightly colored, the female wood frogs are brighter colored. Wood frogs can be identified by the black patch just below their eyes. They are usually between 1.5-3.5 inches long.

Female wood frogs lay anywhere between one thousand and three thousand eggs in a season. They lay them in vernal pools, pools of water in forests that appear in the spring after the winter thaw and gradually disappear as the summer goes by. These eggs take between nine and thirty days to hatch, depending on temperature and other conditions. The tadpoles eat algae and other plant material for the most part. Once they go through their lifecycle and become young frogs, they go on to eat insects, spiders, worms, slugs, snails, and more. Sometimes they even eat tadpoles. It takes around one or two years for the wood frogs to become mature enough to lay eggs of their own.

Wood frogs have several predators, including snakes, birds, and snapping turtles. Their tadpoles are often eaten by large beetles, salamanders, turtles, and other frogs. While wood frogs aren’t endangered, their habitats are being threatened by urbanization as well as climate change.

These amphibians are the only frogs to live north of the Arctic Circle. How do they survive the bitter cold winters of the arctic? Like other frogs, wood frogs hibernate. They bury themselves in leaves and other matter that is on the forest floor. When they hibernate, they stop breathing and their hearts stop beating. Yet they don’t freeze. Their secret power is in their pee.

Wood frogs can hold their pee for several months. I guess it stands to reason that if your heart isn’t beating, the rest of your system isn’t working either. The main ingredient in pee, urea, has a lot of nitrogen in it–that’s why pee smells like ammonia. Instead of excreting this urea out of their bodies, like we would when we pee, wood frogs store it in their cells when they hibernate. This acts as a sort of antifreeze, and prevents ice from forming inside the cells, which would be very bad. If ice formed in the cells, the cells would rupture as the water in them crystalized and expanded. While ice does form between the cells in their bodies, the cells themselves are safe. When the weather starts to warm up again, the frogs thaw out and their bodies start to function normally again. Their hearts beat, they breathe, and yes, they pee.

Want to learn more about vernal pools, where wood frogs lay their eggs? Go read my article about them, and then see if you can find one!