Southern Tree Frog

Hyla squirella Bosc

Colour: Green or brown; bright or dull, of light or dark shade. There is a dark patch from the eye to the shoulder, including the ear; a dark line from the nostril to the eye; a light line along the jaw from under the eye to the shoulder. This light line may be continued along the sides half-way or all of the way to the posterior part of the body, and may be margined below by dusky colour. There may be a V-shaped dark mark between the eyes and round or elongated spots on the back. There may be much orange-yellow on the throat, under the arm at the place of its insertion, on the two inner fingers, and posteriorly on the concealed parts of the body, femur, tibia, and tarsus (parts concealed when frog is in resting position). Eye bright orange-yellow or bronze. Ear brown, metallic. Legs irregularly barred or not. The concealed leg surfaces are not spotted nor vermiculated. (Distinctions from Hyla femoralis and Hyla versicolor.) (See Colour Plate X.)
Measurements: Size small, i.e. length 1 inch to 1 2/3 inches. Length of head contained three and a half times in total length. Length of leg to heel equals length of frog forward to end of muzzle. Tibia and femur of equal lengths. The knee touches the elbow when the arm and leg are pressed against the body.
Structure: Skin smooth and fine in texture. Head somewhat acute, rounded in front. Canthus rostralis prominent. Nostril nearer to end of muzzle than to the eye. Ear two-thirds size of eye. Eyes widely separated. A fold of skin across breast. Disks on fingers and toes well developed. Inner sole tubercle small; no outer sole tubercle. Tubercles under joints of toes somewhat prominent. Webs short.
Range: Hyla squirella Bosc is found in the southern part of North America, its range extending well up the Mississippi. It is reported from North Carolina, South Carolina, Georgia, Florida, Louisiana, Mississippi, Texas, and southern Indiana.

Hyla squirella is a delicate, smooth-skinned, little tree frog, and is one of the most active in North America. It is a most difficult frog to catch, giving leap after leap in rapid succession and in changing directions. If we do succeed in catching a half a dozen and carry them home in a pail or box, there are few chances but that we shall lose most of them the moment they are uncovered. They do not wait to be lifted out; they do not climb onto one's finger and cling confidingly; they jump simultaneously with the opening of the box, all in different directions.

Of all the tree frogs of North America, this one has perhaps the greatest power for rapid colour change, and during these changes presents the greatest variety of colours and shades of colour. At any given moment Hyla squirella may wear any one of the following costumes: unspotted dark chocolate brown or dark brownish olive; light purplish brown with dark brown spots; light yellowish or greyish brown without spots; any medium shade of brown with green spots; olive green unspotted; light yellow green spotted with brown; unspotted light pea-green; light greenish gray; light fawn colour, or still lighter shades ranging down to flesh colour.

Most curious is the fact that although these changes take place under the influence of various stimuli, such as light, moisture, and heat, they may go on without these stimuli. Frogs shut in a dark pail with no change of conditions will not appear twice alike when the pail is opened at intervals during the space of several hours. Some may be green and others brown; some spotted, others not; some light while others are dark. And at any given time of observation those that were dull and spotted before may be bright unspotted green, the ones that were light may be dark, and so on. The light line along the jaw undergoes great changes also. This tree frog furnishes a most interesting case for the study of metachrosis.

Hyla squirella lives on either low or tall vegetation. It may be found on the vines and shrubs of the garden or the river and lake margins, or it may climb into the trees of similar localities. It conceals itself under the decaying bark of trees or under dead logs. It is said to hibernate in old logs.