Common Tree Frog — Part 2

Hyla versicolor Le Conte

In September, when we climb the apple tree to get more perfect apples than those which have fallen to the ground, we put our hand on a lichen-covered branch only to find it soft and alive under our touch. We go hazel-nutting along the country road, and the first cluster of nuts that we pull from under its umbrella of leaves has a green tree frog on it.

And so we know this tree frog well. We learn to expect him in the orchard and about the house in early summer and to miss him again early in September, when he disappears for his long winter's sleep in some cozy hollow among tree roots or in a tree trunk.

We know his voice also, though perhaps we have never actually watched him sing. At dusk or on rainy days a loud resonant trill comes from the trees and vines. The sound has the charm of contentment in it; in fact it is much like the purring of a cat, only louder. At a distance it sounds something like the bleating of a lamb. The pitch is uniform, but may vary with the individual, from G above middle C to E above. It continues for two or three seconds at a time, then ends abruptly. It may be given several times in rather close succession. If we see the tree frog trilling, we are surprised that the whole body is so greatly agitated and that the throat extends into so large a sac. The size of the sac decreases between each two trills and at the end collapses, leaving a very wrinkled throat.

The fact that the tree frog calls during damp weather, and therefore often before storms, has made him accepted as a weather prophet; however, he can scarcely be called a reliable one.

The Common Tree Frog measures about two inches in length. The head is broad and blunt, the body is fat and squat. The skin is granular and has the appearance of being much too large for the frog. The tree frog is like the frogs in having teeth on the upper jaw. The eye is large; the ear is inconspicuous. The fingers and toes have their ends extended into broad disks that secrete a sticky substance on their lower surfaces. The toes are webbed as far as the disks; the fingers are webbed nearly one-third of their length. The male and female are more nearly alike than is usual among tree frogs. They may not differ in size or color, except that the throat of the male is dark. They can be distinguished from one another by the ears, which are always smaller in the female than in the male.

The colour varies greatly at different times and in different conditions. (See Colour Plate VI) In bright light and high temperature it may be yellowish white with no markings. In a dark, moist or cool place, it may be a deep stone-grey or brown. Most often, perhaps, it is bright grey with dark markings. The most conspicuous of the markings are the two bands on each leg and each arm, and the irregular star on the upper part of the back. There is usually a conspicuous lighter spot just below the posterior half of the eye. This tree frog can always be distinguished from tree frogs resembling it by the vermiculations of brown and yellow on the concealed leg surfaces. (See Colour Plate VI.)

However, we have not exhausted this tree frog's possible change of dress when we have considered all gradations between white and stone-grey or brown. There is almost as wide a range between white and green. When the background of colour is green, his characteristic markings may or may not appear. Also, there may be various combinations of the green and the grey. One of the most attractive of his suits is bright grey, with dark grey markings broadly bordered with bright green.

The underparts are light. There is much orange-yellow on the body and legs where they fold against one another. This colour is very conspicuous when the tree frog leaps.

The changes in colour are not rapid, an hour at least seeming necessary to create any radical difference. But it is usually true that the given dress--whatever it may be--harmonizes so perfectly with the surroundings--whatever they may be--that the tree frog is as invisible as though he were Perseus in his charmed helmet. Whether his resting-place be a green leaf or a plant stem, the bark of a grey birch or a lichen-covered oak, (Figs. 134 to 137), his dress and his ability to keep perfectly still for hours at a time form an excellent protection. Chance may bring him to our hands many times in a summer, but he is very difficult to find if we make definite search.