Forest Preserve District of Cook County, Illinois
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Tree Frogs
Nature Bulletin No. 79   August 17, 1946
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation

The tree frog, or "tree toad", is popularly supposed to forecast rain; probably because he prefers humid weather and, after the mating season, sings only on warm sultry or rainy nights and occasionally on dark rainy days. Seldom seen, its clear melodious trill is usually supposed to be that of sore bird.

They spend most of the summer in trees and thickets, feeding on many kinds of insects, and winter in hollow trees, under stumps, or in other cavities.

Like all frogs and toads they must mate and lay their eggs in water. In late spring or early summer the tree frogs seek a woodland pool or quiet backwater containing aquatic plants and protected by high vegetation along the banks. Each female lays 1000 to 2000 eggs in a series of small blobs that stick to submerged stems and leaves. In 4 or 5 days small tadpoles hatch out. Equipped with gills, they live in the water. In 45 to 65 days these change into young frogs that promptly go up in the trees.

This "metamorphosis" is a gradual and complicated process. They lose their rows of horny "baby teeth". The tiny mumbling mouth stretches into a grinning gape that can swallow bugs as big as the frog itself. The intestine, as the diet changes from algae "hay" to insect "meat', shrinks to a fraction of the length that it was in the tadpole. The gills are absorbed and the lungs begin to breathe air. The tail is absorbed; it does not drop off. The front legs break through the skin that has grown over the gills; the hind legs grow long and powerful: so powerful that the frog's tremendous leaps make it appear to fly. Its four toes on each front foot and the five on each hind foot all have moist discs like suction cups at the tips which enable it to cling to smooth surfaces or perform astonishing acrobatics.

They are remarkable for their ability to change color but these changes, requiring an hour or two, are not made at will to harmonize with their surroundings. Apparently these changes are influenced by the temperature and humidity. The under side of the thighs is bright yellow or orange but the back of the body and legs may be various shades of brown, gray or green -- some of them mottled.

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