Northern Frog

Rana septentrionalis Baird

Colour: Light olive, with or without coarse vermiculations of darker colour. There may be large irregular blotches of brown on the sides and posterior back. No light stripe along the jaw. Legs blotched or transversely banded. Underparts light yellowish, unspotted. Buttocks yellow, with dark blotches. Posterior surface of femur may be strongly reticulated with dark colour.
Measurements: Size medium, i. e. length 2 to 3 inches. Leg measurement to heel equals body measurement forward to the eye. Tibia and femur about equal in length.
Structure: Skin relatively smooth; finely pitted when examined closely. Underparts smooth. Buttocks but slightly granulated. Body rather stout. Head narrow, rounded in front. Space between the eyes narrow. Nostrils large, halfway between eyes and tip of muzzle. Ear larger than the eye in the male, smaller than the eye in the female. No lateral folds, or only slight traces of them. Feet long, toes provided with long, broad webs. Inner sole tubercle medium in size.
Range: Rana septentrionalis is wholly northern in its distribution. It is reported from the Adirondack Mountains, from Lucknow, Ontario, and Fort Ripley, Minnesota, and from Moose River and the Hudson Bay region.

It is thought that this species is intermediate in its characteristics between some more primitive form and nearly all the North American species of Rana. From some such form might have come all of our frogs, except, perhaps, the black-cheeked ones, such as Rana sylvatica, Rana draytonii, and the like. It shows close relationship to the Green Frog (Rana clamitans) and to the Bullfrog (Rana catesbiana).

The Northern Frog is described as decidedly a river frog; it is never captured in lakes and ponds. It is silent and unobtrusive, solitary in habit, and thoroughly aquatic. We do not see it in meadows or woods, but if we walk along the brook margin or river bank, it will dive into the water, much as does the Pickerel Frog (Rana palustris) in a similar situation. It hides under stones, among water-plants, or in the mud near the centre of the stream, and may not return to the surface for fully a half-hour. In this habit of remaining long under water when frightened, it resembles the Common Leopard Frog (Rana pipiens). When it does appear, just head and shoulders are thrust out among the water-weeds at the border of the stream. The Northern Frog eats water-insects, and sometimes small fish.

The breeding-season is in June and July. (June 24 and July 30, 1883. Dr J. H. Garnier, Lucknow, Ontario.) The egg-masses adhere to water-plants, and wave back and forth with the current half-way between the surface of the water and the bottom. Two years are required for the development and metamorphosis of the tadpole. The full-grown tadpole with developing legs may measure four inches in length, two and one-half inches being the measurement of the tail. The tadpoles are the scavengers of the brooks and rivers. For instance, they will greedily eat a dead brook-trout, leaving only a perfectly cleaned skeleton.

Both the frogs and the tadpoles give off a strong, disagreeable odour when annoyed. This odour is said to be like the scent of the mink, and this species of frog is often called the Mink Frog.