Northland Nature: Spring frogs wake, sing
Retired teacher Larry Weber, of Barnum, is the author of “Butterflies of the North Woods" and “Spiders of the North Woods," among other books. Reach him via Katie Rohman at email@example.com.
April is such an amazing month of change and we have seen it again this year. Early, we had temperatures of less than 10 degrees and a week later, we climbed to 70 degrees. In this warmth, melting of the ample snowpack formed high waters that we will remember. Warmth and longer daylight served as an alarm clock, waking those that slumbered through the cold.
Along with seeing the returning migrants at this time, we also noted the waking of others. While warm wandering, I noted the waking of a bear, chipmunk and bat among the sleeping mammals. (Earlier, raccoons and skunks were here, too.) In the afternoon sunlight April 14, I watched a groggy mourning cloak butterfly, recently awake from a hibernation of its own, spread its wings and bask in the vernal light.
Other hibernators, later to wake up, include bumblebee, other butterflies and caterpillars, snakes and frogs. This diverse group has in common that they went into the soil subsurface for the winter. Some go quite deep; others just slightly out of the weather. And they stayed below the long-lasting snowpack. (This year, the snowpack was 20 inches or more for nearly four months, mid-December to mid-April.)
Though it may feel cold to us, snow is a good insulator and remaining beneath is a safe wintering site. Some of these waking critters may not be noticed when they rise, but not the frogs.
Three of the Northland eight frog species winter in the bottom of lakes and ponds: leopard frog, green frog and mink frog. Due to the persisting ice, they will not emerge for a while. The other five kinds winter on land: wood frog, chorus frog, spring peeper, gray treefrog and the American toad. They go under the protection of logs, leaves or the soil itself. Many will emerge near wetlands.
As the temperatures rise and the moisture of the snowpack escapes to lower sites and forms vernal ponds, waking frogs respond. These bodies of water, often drying up in summer, serve a vital role in the lives of small amphibians. Quickly upon waking, they make their way to the closest vernal ponds and commence to their next phase of life: mating and laying eggs.
These ponds give the needed water for their reproduction, but the water is still quite chilly. The timing is important for the developing tadpoles. The early-rising males need to get the attention of females, mate and lay eggs. He does this by using his voice to attract her. Within days of waking, wood frogs and chorus frogs sing amorous tunes at the ponds.
Male wood frogs give a “quacking-like” sound, often described as “gluck, gluck.” It is easy to mistake this as coming from other animals. Chorus frogs give a creaking song that has been compared to running a thumb down the teeth of a comb.
They may be hard to view, but when seeing them, wood frogs are about 3 inches long, colored gray to reddish-brown, with a black patch below the eye. Chorus frogs, about 1 inch long, have gray to green stripes on the body.
While chorus frogs will continue to call for a couple weeks, wood frogs have a short breeding season. Both species go off to spend the summer in the woods.
Another small, 1-inch frog, the spring peeper, will quickly add its high-pitch notes to the sounds of the vernal ponds.
These singing frogs are a regular event of spring. They tell of surviving the winter and continuing the species in coming months.