Spring fever hits just as the air begins to warm above freezing. Sunny days beg you to get out to explore your local woodlands, and you gratefully soak up the warmth through the leafless trees. As you amble along an old logging road you become aware of a sound a short distance away. You know there is a wetland up ahead, but it is far too small to hold the vast number of ducks you hear quacking. As you approach, a closer inspection reveals a seemingly empty, and now silent, vernal pool. What’s going on?
The wood frog (Rana sylvatica), as its name implies, lives in woodlands, not water, and spends the winter hibernating beneath logs, rocks or leaf litter. Two to three inches long, it is a brown frog, not green, and individuals vary from chocolate to tan to rust. A distinguishing characteristic is the black mask that runs through the eye – a bandit frog. Another cool thing about this frog: antifreeze compounds in its body allow it to survive freezing during the winter months. It is amazing to think that this frozen amphibian will thaw in the spring to once again go about its business.
The first “warm” rains of the season compel the wood frog to migrate to its natal vernal pool where it congregates with dozens, or hundreds, of other wood frogs. It is a race against time for these frogs to breed, their eggs to hatch and the tadpoles to develop into land-dwelling froglets before the vernal pool dries up in the summer. This is the one brief time in the year when you will find these frogs in water. While there, the males use an “advertisement call” to lure the females in. This call is very similar to the quack of a duck and when many wood frogs are calling, the sound can be deafening. But when disturbed, they dive to the pool’s bottom until the coast is clear.
If you can be patient, find a dry place to sit still for a bit. Eventually the wood frogs will pop up to the surface to resume their courtship and mating. You may see a smaller, darker male clasping onto the back of a large rust-colored female. She is laden with eggs. As she lays a small gelatinous mass that contains hundreds of eggs, she attaches it to a submerged twig and the male fertilizes it. Over time the ping pong ball-sized egg mass will expand to about the size of a softball. By then the adults have left the water to resume their quiet, solitary lives among the leaf litter on the forest floor.