Pacific Tree Frog

Hyla regilla Baird and Girard

Colour.—Extremely variable. Any shade of grey, brown, or green; occasionally distinctly red. A narrow black or dark brown band extends from the nostril (or from the muzzle) to the eye, and, widening behind the eye, continues through the ear to the shoulder. This dark band is bordered below by a band of light colour. The immediate line of the jaw is dark. (Fig. 166.) The dark band which passes through the ear may be continued along the sides of the frog in a series of black spots. There may or may not be a V-shaped mark between the eyes, extending well up on the eyelids, and elongated dark spots placed lengthwise along the back and upper sides. Underparts dark or light. Throat of male always darker than remainder of underparts. (Fig. 169.) The undersurface has much orange colour posteriorly. (See Colour Plates VIII and IX.)

Measurements.—Size small, i. e. length 1 1/4 to 1 3/4 inches. Leg long; length of tibia equal to length of femur, and equal to half total length of frog.

Structure.—Skin finely tubercular above, granulated below, except for the throat region. (Fig. 169.) Canthus rostralis very distinct. (Fig. 165.) Ear distinct, less than half the diameter of the eye. Head obtuse in front. Disks on fingers and toes relatively small. Fingers long, not webbed. Toes webbed half their lengths. (Fig. 169.)

Range.—Hyla regilla has been reported from Washington, Oregon, California, Nevada, Lower California, and from Cerros and Santa Cruz islands, which are twenty miles from the Californian mainland. This makes its range cover an area from Vancouver Island on the north to Cape St. Lucas at the south, and from the islands of the coast to the eastern base of the Cascades and Sierra Nevada. In the region of Washington and Oregon, its range extends well into the desert part of the Great Basin, following the streams of the country. In Death Valley it is found at isolated springs and wells, more than half-way across the Great Basin. There is no authentic report of its occurring in Texas. "Moreover, it may be noticed that in altitude Hyla regilla ranges from sea-level to 10,000 feet in the vicinity of Mount Whitney. Thus it occurs from the Lower Sonoran well up into the Boreal Zone, equal to the difference in latitude between Florida and Labrador, and the extension of its range is thus second to that of no other Hyla in North America." (F. C. Test. "A Contribution to the Knowledge of the Variations of the Tree Frog Hyla Regilla." Proc. U. S. Nat. Museum, vol. XXI, pp. 477-492.)

If we capture several specimens of Hyla regilla, we are almost immediately impressed by three facts: first, their great alertness and activity; second, their great variation in colour and colour pattern; and third, their rapid and marked colour changes.

They are not quite as active and impossible to manage as Hyla squirella of the Southern States; they compare more favourably in activity with Hyla pickeringii of eastern North America. These frogs are small, with bodies relatively slender and legs unusually long, so we are not surprised at the number of the leaps made and the distance covered with each movement. They show little tendency to climb, and will remain at the bottom of an uncovered moss-garden for days at a time without any attempt at escape.

Their variation in colour is great. They may be any shade of grey, green, or brown, and sometimes are more or less vividly marked with red. It is not to be wondered at that one not familiar with the fact that colour is seldom a specific characteristic should think that the lot contained several kinds of frogs. Most of the frogs present only one colour or shade, but there are likely to be several in a given lot that will combine two shades or two colours. The back may be brown while the sides are green, the head and shoulders may be red while the body posteriorly is green, and so on. (See Colour Plate VIII.)