Wood frogs: Early spring singers tune up in the Berkshires
For some, it's the first pussy willow that marks spring. Not me. I have seen them in all their fullness in January and February. For others, it is seeing the first robin or bluebird. Not me. These birds are with us all winter. Yet others claim the spring peeper to be the true harbinger of spring. Not quite, but close. It is hearing the first wood frog issuing his quacking-like, mate-attracting song that marks spring for me.
I first encountered the wood frog sometime in the 1960s while looking for early spring birds. In the open woods of the Sheffield flats, thick with shrubs and young trees, I heard ducks calling in the distance. Heading toward the sound, I was stunned at how close the "ducks" were, yet I could not see them. On my noisy arrival at the place where I was sure they must be, that they "just disappeared." Somewhat frustrated, I sat on a log, and after a few quiet moments passed the "ducks" began quacking again, only they weren't ducks but frogs -- 2-inch beige-colored wood frogs with a dark, raccoon-like mask over the eyes.
Tom Tyning, Berkshire Community College professor and noted authority on amphibians and reptiles, explains, "Frog and salamander movement is all based on temperature and rainfall. If it's above 40 degrees, but the ground is still frozen, then only peepers and wood frogs will move -- they have freeze-tolerance mechanisms that let them spend the winter just in the leaf litter on the forest floor. They can freeze and thaw several times a winter before getting going for the season.
Peepers, historically, have been heard every month of the year in New England.
"Once the ground thaws, and it's above 40 degrees, and it's very humid or raining, then many of the spring amphibians (especially the vernal pool users) will undergo their great migrations. (Sadly, many won't make it across the roads).
"If it stays warm, but we have little or no rainfall, then wood frogs will migrate anyway, especially in the daytime. They can't wait too long to get to the pools. They migrate, court, lay eggs and leave the pool in a matter of a few days; typically less than a week. Then the eggs have to incubate, embryos develop, then hatch, then try to simultaneously avoid predators and find food, then grow big enough to metamorphose [change to adult form] before the vernal pool evaporates."
Wood frogs have always been kinder to early springtime frog enthusiasts. This frog does not care about temperature, provided it is above 40 degrees, or whether it is day or night, provided some open water allows for mating and egg laying.
They spend winter below woodland leaf litter, protected from the deep-freeze during their long winter's sleep by producing high concentrations of glucose, an anti-freeze. The first warm rains call them to order. Listen for their "quacking" in woods, where they will call from shallow ponds.
For this species. successful breeding is a race against time. After a dry winter and equally dry spring they may not have enough water in the snow-melt pools they favor for eggs to hatch and tadpoles to develop into froglets before the pool dries. In such years they experience 100 percent offspring mortality.
These temporary woodland pools, called "vernal" because they appear in the spring, have no outlets and usually fill because of melting snow and winter's freezing rain.
Of the 10 species of frogs and toads that call Massachusetts home, the best known, besides the bullfrog, is the tiny, less-than-an-inch, spring peeper.
And it is always motivating to hear their first chorus, proving that a new season has come.
Anyone lucky enough to actually see a peeper can easily identify it by size and the "X" mark on the back. Unlike the wood frog, this species can be found in wooded wetlands, along shores of beaver ponds and almost anywhere shrubs and water mingle.
The American toad is another early spring songster that trills rather than peeps or quacks. Its continuous call or trill can last nearly half a minute. Together, a cluster of eager toads produce a pleasant din that appears to last for hours.