Western Frog — Part 3

Rana pretiosa Baird and Girard

Rana boylii, which, in California, is called the Yellow-legged Frog, has perhaps the most toad-like appearance of any frog of North America, although it does not sit erect in toad fashion. The likeness lies in the texture of the skin. The short, flat body is completely covered with small warts, from the tip of the nose to the ends of the feet, producing a surface that at first glance has somewhat the appearance of coarse sandpaper. The frog is usually olive, grey, or yellow-brown, obscurely spotted on the back (Colour Plate II), but often the whole tubercular upper surface is bright brick-red. This red is sometimes to be seen on the lateral folds and on the tibia, when the frog is brown or olive elsewhere.

Rana boylii is excessively shy and wild. Its first instinct is to hide. It scuttles head-first under cover at any approach. If there is no place of concealment, or if its hiding place is disturbed, it leaps great distances, and the enemy who can capture it must be alert of sight and grasp. This frog emits a curious, oily odour, greatly like that given out by the California Toad, Bufo halophilus.

It has great power to change its colour from dark to light, appearing nearly black at one moment, and light reddish or yellowish grey half an hour later.

Rana boylii is one of the most distinct species of frogs in North America. Within its own range, the yellow colour of the underparts will suffice to distinguish it, since Rana draytonii, Rana aurora, and Rana pretiosa, the other frogs of the Pacific Slope, have red instead of yellow in the colouration. Compared with all the frogs of North America, it is peculiar in the tubercular character of the skin, though some specimens of Rana draytonii approach it in this characteristic. Rana boylii is like Rana pretiosa, Rana catesbiana, Rana grylio, and Rana septentrionalis in the extensive webbing of the feet.

Rana virgatipes and was first discovered by Cope, at Atlantic City, in 1891. It was found in company with Leopard Frogs and Green Frogs, in stagnant water, where sphagnum moss, bladderworts, and water-lilies grow. In the summer of 1905, it was reported as very abundant near this type locality. (Fowler, Acad. Nat. Sci., Philadelphia.)

These frogs have been seen at Lakehurst, at intervals from May to September. They occur rather abundantly in the ditches about the cranberry-bogs, as well as in the lake itself. They are often found seated on a lily-pad or on the sphagnum moss. (I am indebted to William T. Davis, New Brighton, N. Y., for these facts, as well as for material.)

Rana virgatipesis decidedly a water frog, and is one of the least hardy of the North American species. It has only average powers of leaping and swimming, but its instincts for hiding are strong. When disturbed, it disappears at once under floating water-weeds.

It differs from the other smaller frogs of North America in the great development of the eyes and ears. It is like the bullfrogs in lacking the lateral folds. It resembles the Leopard Frog, in that the male frog has large vocal sacs that can be extended at the sides behind and under the ears. It shows close relationship in structure and habit to Rana grylio (pp. 227 to 227).