Protecting and enhancing the natural values of Salt Spring Island and its surrounding waters

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Northern Red-legged Frog

Northern Red-legged Frog

Rana aurora, breeds in marshes, ponds, lakes, and slow-moving sections of streams. While vocal during the breeding season, these frogs are seldom heard, as males usually call while submerged under water. When not breeding, they can be found on the forest floor, often along stream banks or pools but sometimes far from water in moist situations. Adults are up to about 70 – 100 mm in body length, females being larger than males. Newly metamorphosed young are about 18 – 40 mm long. On each side of the body, there is a longitudinal fold (dorsolateral fold). The back and sides are brown with black flecking or irregularly shaped spots; the upper surface of the legs has dark barring. Diagnostic features include a dark facial mask, groin mottled with yellowish green and black (seen when the hind leg is extended), and translucent red underside of the hind legs with the red often extending to the lower abdomen. The red colouration intensifies with maturity and may be indistinct or lacking in small juveniles.  Eggs are laid very early in the spring during a short breeding season. They are in large (about 10 – 15 cm diameter) globular clusters of soft jelly, each containing up to about 2000 eggs. Individual eggs are large (up to 3 mm in diameter) and surrounded by a thick layer of jelly. During later developmental stages the clusters often spread out and float on the surface.  Tadpoles are tan or greenish brown with light and dark flecks and gold or brass-coloured mottling on the sides of the body; the underside is pinkish or off-white with small metallic flecks. The dorsal fin is high and rises abruptly from the middle of the back. The tail is relatively short, rarely more than 1.5 times the length of the body. Tadpoles reach up to about 70 mm in total length (35 mm in body length).

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