Northern Red-legged Frog
|Common Name:||Northern Red-legged Frog
|Scientific Name:||Rana aurora
|Status (COSEWIC):||Special Concern
At a Glance
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.
Home Sweet Home
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.
This is the Life
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.
What’s on the Menu?
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.
Where and When
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
How Are They Doing?
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.
How We’re Helping
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.
How You Can Help
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.