Frogs are amphibians, they have backbones, are cold-blooded, have an aquatic gill breathing larval stage – that means when they are in the water as tadpoles they have gills to breathe, and when they become adults they have lungs to breathe.
Scientists who study reptiles and amphibians are called herpetologists. Herpetologists decide how to classify or group these animals. They give a Latin scientific name to a specific group of animals. The scientific name is the genus and species. This helps so if people have different “common” names, or like many of us have nicknames, they can refer to the genus and species to see if they are talking about the same animal. Funny thing is with the wood frog has two Latin names, Lithobates (the word means “stone”) sylvaticus or Rana sylvaticus, seems like the scientists cannot agree on this one.
Wood frogs are considered to be a “biological miracle”. The reason is, in winter they shelter under leaf litter and logs in woodlands and are able to go into a deep hibernation and can freeze solid. They stop breathing and their heart stops. When the temperature drops they can produce high concentrations of sugar glucose that acts like a special anti-freeze. Although the water around their cells freezes the “anti-freeze” prevents the cells from freezing. When the weather warms up the frogs thaw out and head for “vernal” pools to mate and lay eggs. Because of this ability to freeze, wood frogs are the only frogs found north of the Arctic circle (North Pole).
Wood frogs have a distinctive “mask” over their eyes and two folds (dorsolateral folds) of skin that run from the back of the eyes along the sides of its back. The color varies from a pinkish-tan to dark brown to green or grey. They don’t have webbed feet in the front, but the back feet are webbed and you can tell the difference between the male and females by the webbing. Females have “concave”, curves inward, webbing. Males have webbing on their hind toes that curves outward, “convex”. The males also have brighter colors on their thighs. Adults are 1.5 – 3.25″ in length.
Males are heard making quack like calls. While hiking in the woods and might hear something that sounds like a bunch of quaking ducks. As you get closer to a vernal pool to observe you discover wood frogs instead of ducks! Wood frogs and spring peepers are often the first frogs to breed, usually starting in early March. Males search for a mate by hugging other frogs, females are rounder because they are carrying eggs. Females lay eggs masses with 1,000 to 3,000 eggs. The egg masses are usually attached to plant stems or sticks, sometimes they are free floating. Algae grows on egg masses causing the egg masses to look like pond scum. The algae helps to camouflage them. Depending on the water temperature it can take 10 – 30 days for the eggs to hatch. Tadpoles are mostly herbivores, feeding on algae and decaying plant material, some eats eggs and larvae of other amphibians. Wood frog tadpoles are able to recognize their brothers and sisters and will often group together with them.
Adult wood frogs will eat insects, spiders, worms, slugs and snails by shooting out their sticky tongues. “Predators” include snakes, snapping turtles, raccoons, skunks, coyotes, foxes and birds. Their lifespan in the wild is no more than three years.
Currently the numbers of wood frogs seem to be relatively stable across North America, but in Connecticut as they lose their habitat due to development, especially the vernal pools where they breed, the numbers have seen a decrease.
Once again we can help wood frogs by learning more about them and telling others about how amazing they really are!
Stokes Guide to Amphibians and Reptiles by Thomas F. Tyning
Amphibians and Reptiles of Connecticut and Adjacent Regions by Michael W. Klemens