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Canadian Amphibian and Reptile Conservation Network - Réseau Canadien de 
Conservation des Amphibiens et des Reptiles

Rana aurora
Northern Red-legged Frog / Grenouille à pattes rouges du Nord


Northern Red-legged Frog

Description
The Northern Red-legged Frog is a large, true frog with clear dorsolateral ridges. The colour varies from reddish brown to grey and there may be some dark specks or blotches. In northern populations, these dark blotches do not have light centres. The tympanum is indistinct and the toes are not fully webbed. This species may be distinguished from other frogs by the light stripe on its jaw bordering a dark mask and by its yellow underside with red on the lower abdomen and hind legs. Adults can reach 13 cm.

Call
The Northern Red-legged Frog has a weak throaty call lasting two to three seconds. Calling sometimes occurs deep under water and does not carry far.

Confusing Species
The only true frogs which naturally co-exists with the Northern Red-legged Frog are the Columbia Spotted Frog and the Oregon Spotted Frog. All these species have a light stripe on the jaw, but the Spotted Frogs may have a mask or reddish undersides although not always. In contrast to the Northern Red-legged Frog, the toes of the Spotted Frogs are fully webbed and the eyes are slightly upturned. The Wood Frog looks superficially like a Northern Red-legged Frog as it does have a mask and may have dark specks on it. Wood Frogs are occasionally reddish above however their underside is white with dark mottling.

Distribution
The Northern Red-legged Frog has a very limited distribution in Canada, being only found in southwestern British Columbia, Vancouver Island and other nearby islands. This distribution continues southward along the west coast of the United States and into Mexico.

Habitat
Northern Red-legged Frogs are usually found in or near well vegetated permanent water. In parts of their range they may be found at up to 2,400 m above sea level.

Reproduction
Breeding occurs in late winter or early spring. Eggs are laid in a loose cluster on the surface of permanent water bodies. Their eggs are more susceptible to overheating than most other frog eggs and so they require stable water temperatures.

Natural History
The Northern Red-legged Frog is less aquatic than the Spotted Frogs and may be found at the shoreline or foraging on land.

Conservation Concerns
The Northern Red-legged Frog has declined on central Vancouver Island. Competition from introduced Bullfrogs and Green Frogs, and logging activity may be the problem. This species has also declined throughout much of its range in the United States. The Northern Red-legged Frog has been designated Special Concern by COSEWIC