Northern Wood Frog

Rana cantabrigiensis Baird

Colour.—Dark brown to yellowish grey. A dark line from the end of the muzzle extends backward on each side along the canthus rostralis through the eye, to form a large patch of colour in the region of the ear. A light line along the jaw from the end of the muzzle to the shoulder. There may be a light dorsal streak from near the end of the muzzle to the posterior part of the body. Lateral folds light-coloured, and bordered below by irregular line of black. Legs barred or spotted with dark. Underparts light, more or less mottled with dark, yellowish posteriorly.

Measurements.—Size below medium, i. e. length 2 to 2 1/2 inches. Distance between nostrils greater than width of the head between the eyes. Legs long, length to heel just equalling total length of head and body. (Legs shorter than are those of Rana sylvatica.) Tibia equal to the femur and equal to one-half the total length of head and body.

Structure.—Skin smooth. Head pointed. Ear smaller than the eye. Lateral folds not greatly elevated. Web large.

Range.—The distribution of Rana cantabrigiensis is wholly northern. It is reported from Illinois, Michigan, Wisconsin, and Minnesota northward to Great Slave Lake on the west and St. James Bay on the east.

Colour.—Female-Reddish brown on the upper parts, with or without darker spots. The region below and behind the eye (including the ear) may be dark brown in colour. A yellowish band along the jaw from the shoulder to the eye. Arms, legs, and upper sides irregularly spotted with dark; the legs may be transversely barred. Underparts light, spotted, and marbled with dark. Lower sides of body and underparts of legs and feet bright red. Rich mosaic arrangement of black and yellow on upper leg and side of body where they rest against each other. The male is less rich in colouring. It is greyish brown or yellowish, is more likely to be distinctly spotted, and has much less red. In both sexes, the palm of the hand and the sole of the foot are purplish grey in colour. (See Colour Plate XV.)

Measurements.—Size large, i. e. adult males 2 1/2 to 4 1/2 inches females still larger. The length of the head is contained three times in the total length of head and body. The lower leg is somewhat longer than the upper leg. The length of the leg to the heel is not as great as the combined lengths of head and body.

Structure.—The skin is tuberculated, especially in old specimens. Buttocks granulated. Head broader than long, rounded in front. Body broad and heavy. Canthus rostralis fairly prominent. The ear is smaller than the eye. A glandular ridge extends backward from under the eye, narrowing to the arm. This ridge is interrupted at the angle of the jaw, and also back of this, where the curving ridge descends from the eye to the shoulder. The lateral folds are distinct, and are perforated with minute pits. There is a conspicuous fold of skin over the ear from eye to shoulder. The legs are massive in full-grown specimens. The tubercles under the toe-joints are especially conspicuous. The inner tubercle of the sole is medium in size; the outer, small or lacking. A distinct tarsal ridge. The fingers are unusually long. The first is thickened at the base (male).

Range.—Rana Draytonii is reported from various parts of California, also from the mountains of Lower California. (From Petaluma, El Dorado, Presidio, Fort Tejon, Carmel, San Francisco, and South San Francisco, California.)

Colour.—Brown, yellowish, or olive, often matching the colour of dead leaves. There may be small spots or specks of dark brown or black on head, back, and sides. Space behind the eye and including the ear may be black. A black line below canthus rostralis from eye to jaw. Iris golden yellow. Glandular fold from under eye to shoulder, yellowish. Upper and lower lips spotted with dark. Arm may be crossed by 3 to 5 narrow dark bands. Much red in the colouration, showing on the parts of legs and feet which are concealed when folded, on the sides of the body, and under the arms at their insertions. Reticulations of yellow and black on body and femur where they lie against each other. Throat and underparts light, obscurely mottled with dark. Hand and foot may be purplish grey in colour.

Measurements.—Size medium, i. e. length 2 1/2 to 3 1/2 inches. Length of head enters total length three and a quarter to three and a half times. Leg very long, its length to the heel exceeding the total length of the head and body. Tibia much longer than femur.