Wood Frog

Lithobates sylvaticus

Previously Rana sylvatica the wood frog is the ubiquitous Albertan frog. It is found in water bodies large and small over all but the driest southeastern corner of the province. This is the frog you find hopping across the hiking path or sharing your back yard. To identify this frog from others you may come across there are several features to look for. Generally a shade of brown, this 3-6cm long frog is most known for it’s dark brown mask. This mask starts thinly at the nose and runs through the eye to just past the ear drum, which is smaller than the eye. Accentuating the mask is a white stripe just below it on the upper lip. The wood frog also has prominent dorsolateral folds (a ridge that runs down each side from near the eye to the groin). Tadpoles are difficult to differentiate because they are so small, but wood frog larvae tend to be lighter green with a cream coloured belly. When walking along a pond’s edge you may encounter wood frog eggs, which are seen as a large clear gelatinous mass with small dark developing larve within. The egg masses are usually attached to vegetation but may be seen free floating. They may include 2000-3000 eggs.

The wood frog has a vast northern range that spans from the east, to the west coast and is the only amphibian species found north of the Arctic Circle. In Alberta, wood frogs are often found far from water, but they are most often found in association with ponds, lakes, flooded farmland and sloughs, bogs, and also along river and creek valleys. They hide, often frozen, in leaf litter, soft soil or muddy banks during the winter and breed shortly after the snow melts. The wood frog call is a soft, ducklike cackle and is rather unique among North American frogs.

Many species of amphibians have shown strong declines throughout the world but the wood frog remains strong throughout Alberta. Draining of wetlands and pollution seem to be it’s largest threats.

The Amphibians and Reptiles of Alberta by A.P.Russell and A.M.Bauer

Photo by Ian Kanda

Wood frog eggs