The Illinois chorus frog is a fossorial amphibian. I think it should be our state fossorial amphibian, but I’ll get back to that later.
After a few days Brown emptied the aquaria and counted the mealworms. There were still 500 in the control aquarium, but only about 450 in the other two tanks. And when he “sacrificed” the frogs (scientists always use that term when they have to kill an animal in an experiment; I imagine them operating with obsidian knives, but they probably use stainless steel) he found the missing mealworms, partially digested, in their stomachs. The frogs had fed underground. They lived without coming to the surface.
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I have been in this nature-writing game for many years, but I must confess that I didn’t know there was such a thing as a fossorial frog. I knew about toads hopping about on the ground, and tree frogs living in trees. I knew that frogs and toads could dig into the ground to find a good place to hibernate, but all this aside I figured the rest of the froggy race hung about ponds, lakes, and streams, either hiding in the reeds and rushes or sitting on lily pads.
Since I began looking into the habits of frogs and toads, I have found that there are quite a few members of the order Salientia that burrow either for safety or to look for food. Most of them dig with their back legs. Spadefoot toads, for example, have a sharp-edged structure on the inside of their hind feet that helps them dig.
The problems of the Illinois chorus frog are very closely related to its mode of locomotion. Since it spends its life digging in the earth, it needs earth that is easily dug. In fact, it is found only in very sandy soils. Ellen Beltz, who just completed a population survey of the species along the lower Illinois River, thinks it is tied almost exclusively to Parkland sands, a particular kind of very fine sandy soil found on the floodplain of the Illinois River.
Beltz surveyed her frogs on cold March nights, driving down back roads that sometimes vanished beneath her car and left her stuck in the sand. She drove about six miles an hour with the windows open, and listened. It was cold, arduous work, and the fact that she was doing it suggests how little we know about this frog. We are still in the stage of learning where it lives. We know almost nothing about how it lives.
