Ministry of Environment
Northern Red-legged Frog
|Common Name:||Northern Red-legged Frog|
|Scientific Name:||Rana aurora|
|Status (COSEWIC):||Special Concern|
The Northern Red-legged Frog is a medium sized brown or reddish frog, with smooth skin marked by small black "freckles." Male frogs reach about 7 centimetres in length and females can be larger - about 10 cm long. The Northern Red-legged Frog is fairly slim and has long, slender hind legs and prominent dorsolateral folds running from behind their eyes down the sides of the back. They usually have a dark mask, and a light upper jaw stripe running back to the shoulder. The most distinctive trait of these frogs, and the one that gave them their name, is the red colouring of the underside of their hind legs. This is sometimes described as being translucent - as though you are looking right through the skin to see the red muscle underneath.
The eyes are gold, oriented to the sides, and appear mostly covered by the eyelids when the frog is viewed from above. This can help distinguish the Northern Red-legged Frog from the Columbia or Oregon Spotted Frogs, whose eyes are oriented upwards. It can be tricky to tell Red-legged and Spotted frogs apart, even for experts, but by looking at the eyes, the skin and the toe webbing, you can be fairly sure of your identification. Spotted Frogs have rougher skin and more webbing between their toes than the Northern Red-legged Frog. Spotted Frogs also do not have the translucent quality to the red wash on the hind legs; rather, their skin appears mottled and the colour almost painted on. Northern Red-legged Frogs and Spotted Frogs have only a small overlap of their ranges in B.C., so it's fairly likely that you could make an identification based on location alone.
Northern Red-legged Frogs enjoy the cool temperatures of the coastal forests. They live in moist forests and wetlands with trees, breeding in shallow ponds or slow streams that are well shaded. Adult frogs spend much of their time on land, sometimes straying quite a distance from the water if the weather is damp. They will often take shelter under logs or other debris to stay cool and damp.
Northern Red-legged Frogs begin to mate and lay their eggs very early in spring - as early as January or February in coastal areas. They prefer shallow, slow-moving streams, ponds or marshes for breeding. Male Northern Red-legged Frogs behave like males of other species in that they call to attract females, but they call from an unusual location - up to a metre underwater. The call is not at all loud, low-pitched, and is sometimes described as a stuttering noise. Females lay eggs in large, jelly-like clusters of 750-1300, attaching the clusters loosely to stems of aquatic plants just below the surface. Embryos develop and hatch in about four weeks, then spend four to five months in the tadpole stage. Tadpoles metamorphose into tiny hopping froglets, only a couple of centimetres long, in midsummer. Northern Red-legged Frogs are thought to take three or four years to become sexually mature.
Adult Northern Red-legged Frogs feed happily on insects and other small invertebrates, which they hunt along the edges of streams and ponds. Tadpoles graze on algae.
Northern Red-legged Frogs are often found in damp wooded areas, but are very shy and will leap away swiftly if they feel threatened. During the breeding season (winter to early spring) they may be found in ponds and streams, but the breeding season lasts only a week or two at each site.
This frog has a limited range in B.C., being found only in the southwestern part of the province: on the mainland coast, in the Fraser Valley, on Vancouver Island, and on some of the smaller coastal islands. The range extends southward as far south as California.
Northern Red-legged Frogs have declined in some parts of their range due to habitat degradation and loss from agriculture, urban development and forestry. Competition from introduced Green Frogs, Bullfrogs and predatory fish is also a factor. Northern Red-legged Frogs are nationally listed as Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and they are on the provincial Blue List. A subspecies of Red-legged Frogs, the California Red-legged Frog, was recently listed as Threatened by the state of California, for similar reasons.
Under the Identified Wildlife Management Strategy of the Forest Practices Code, Wildlife Habitat Areas can be established for important breeding habitats. Scientists are studying the effects of forestry practices on Northern Red-legged Frogs.
Northern Red-legged Frogs are protected under the British Columbia Wildlife Act.
You can help by learning more about these frogs and their habitat requirements, and teaching others about them. You can find out more about ways to protect wetlands through programs such as Naturescape, Wetlandkeepers, and Wild BC. Be an ambassador for the frogs in council meetings and other planning meetings! You can also help biologists learn more about the range, distribution and habits of these and other amphibians by joining BC Frogwatch and observing the frog populations near you.
- "Aurora" means “dawn” and refers to the pinkish colouring of the Northern Red-legged Frog's legs.
- Northern Red-legged Frogs can scoot through forest litter faster than a person can follow them - they make long, low hops and go under the fallen branches that trip their pursuers.
Photo © Wally Edwards. No reproduction or distribution without permission.