Western Frog — Part 2

Rana pretiosa Baird and Girard

Range.—Reported from Atlantic City and Lakehurst, New Jersey.

The Western Frog has been found during the winter, sleeping in the mud under a foot or more of water, along marshy lake margins. It appears in the Puget Sound region from the last of February to the middle of March. A few scattered individuals may, however, be seen on sunny days throughout the winter. These are usually among the lily-pads along the marshy borders of the lakes.

As soon as they appear in March, they set up a noisy croaking, and the eggs are laid between this time and the first of April. The egg-masses are unattached. They vary greatly in size, but average about a pint in bulk. In one case where the eggs were counted, a laying consisted of over fifteen hundred eggs. The eggs are relatively large, measuring nearly 2 mm. in diameter. Each egg is in a transparent sphere of jelly measuring one-half inch across. The eggs are placed in the shallow, marshy pools near a lake, but never in the deep lake-water itself. The length of time required for hatching is from one to two weeks, varying with the temperature; those in the warm, shallow water hatching earlier than those in deep water. The later development is slow, and it is not until after the summer is passed that the tadpole becomes a frog. This slow development is perhaps correlated to the conditions of the region of the frog's range. There is an abundance of water in this region, even in summer, so that the development is not hastened by the drying up of the pools.

From this time on the growth is slow; at least, there can be found, each spring, frogs of four or five different sizes, so that it would seem as though they require four or five years to reach the adult size.

The adults are easily captured during the breeding-season. As soon as we approach them, they dive into the mud of their shallow pool, burying the head and shoulders, but leaving the legs exposed in good position for capture. Their colouring is highly protective. It is difficult to see them when they are sitting among the alternating lights and shadows of the reeds. They depend so much on their protective colouration, that they lie low and allow themselves to be touched before taking alarm. (Many facts concerning this species were kindly furnished by Prof. J. F. Illingworth, Seattle, Wash.)

This frog is distinguished from other Western frogs by its round nostrils, the tubercular character of the soles of the feet, the long foot and large web, and the lack of prominent lines from the nostrils to the eyes. The frog shows no salmon-red colour when in sitting position, and so one's surprise is great on discovering so much brilliant colour on the under surface of the frog's body and legs. The undersurfaces of the arms may have the same colour. The lack of red on the side distinguishes it at once from Rana Draytonii and from Rana aurora, as does also, the lack of dark cheek-patches. The position of the eyes also aids in the distinction.

As to colouration, this frog may be any shade of yellowish or reddish brown, from the lightest to the darkest. The sides are always lighter than the back. The legs are irregularly barred and spotted with brown. The knees are likely to possess the same light yellowish grey colour of the lower sides. The male is considerably smaller than the female, and is likely to be more spotted. The forearms are muscular, and the first finger is thickened and hardened at its base. The feet and webs are enormous for the size of the frog. The web has a spread of one and one-half inches on a frog only two and one-half inches long.

When taken in the hand so that its feet are unsupported, this frog "talks" vigorously, as do many of the frogs and toads. This is true of both male and female, but the voice of the male is louder and more emphatic. External vocal pouches do not show when the frog croaks.

The Western Frog is thoroughly aquatic in its habits. It gets its food largely from the water, feeding greedily on small fish, as does its near neighbour on the Western coast, Rana draytonii, and as does the Eastern Bullfrog.

It is interesting to watch the male swim in very shallow water. With flattened body and lowered head, he searches for something under which he can hide. Finding nothing, he kicks out his powerful legs, alternately spreads and folds the extremely large webs, and continues the search. He sometimes turns so sharply, that the body is entirely turned around before the legs have had time to turn, and so for the moment one leg ludicrously measures itself straight forward along the body. Finally, some bit of moss is found under which the frog can push his head, and there consider himself safe. So safe does he feel, that almost immediately he lifts his head till nostrils and yellow eyes are above the weeds and water. The eyes are peculiar, in that they are little elevated at their upper margins, and so face upward more nearly than sideways. This is one of the many characteristics that adapt this frog to a thoroughly aquatic existence.