Chorus frogs are singing. Even after cold nights that leave a skin of ice on the breeding ponds you can hear this lovely sound of spring as the sun begins to do its warming work. The songs of chorus frogs–to be precise, our local animals are western chorus frogs–are like the rasping noise made by somebody dragging a thumbnail across the teeth of a comb. This is a generalized description. According to Conant and Collins’s A Field Guide to Reptiles and Amphibians, the “sound may be roughly imitated by running a finger over approximately the last 20 of the small teeth of a good-quality pocket comb, rubbing the shortest teeth last.” Your cheap pocket combs are not going to fool anybody.
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Their principal habitat in ages past was undoubtedly the prairie, a place that offers few opportunities for climbing, but they have been able to move into farm fields and even suburban neighborhoods where pesticides are not used too heavily. You can hear chorus frogs in the city at North Park Village and in various parks and cemeteries. They’re the most likely frogs to hang on in an urban environment, though how potential mates can hear the songs of the males over all the traffic noise is beyond me.
Male frogs sing to attract females, and females seem to respond strongly to large choruses. A single chorus frog in a tiny pond may get no response at all. A massed chorus of a large number of males apparently signals listening females that the pond is a really great place to have a family. The massed chorus also makes it impossible to tell where one frog’s song leaves off and another’s begins. Imagine 50 people with good-quality pocket combs all simultaneously scraping their thumbnails along the last 20 teeth.
You often hear complaints these days about how the government is forcing landowners to preserve tiny wetlands, the implication being that vernal ponds that cover only a couple of acres can’t be of much use. But the frogs I heard last Sunday were singing in ponds of less than an acre. One was only a few thousand square feet. The value of these tiny wetlands is considerable, and it increases if the small wetlands are part of a complex of scattered wetlands. Frogs are mobile enough to get from one of these wetlands to another, and so are turtles. A couple of years ago a female Blanding’s turtle with a small radio transmitter attached to her carapace was tracked wandering north from Bluff Spring Preserve, a Lake County forest preserve north of Zion, into the Chiwaukee Prairie in Wisconsin. The animal covered about half a mile from one marshy pond to another, and in the process became a threatened species. Blanding’s turtle is considered “threatened” in Wisconsin but not in Illinois.
