Wood Frog
Last Review/Updated: May 30, 2002
Rana sylvatica
Description
The smallest true frog in Alberta, the wood frog ranges from only 30-60 mm in length. It is easily recognized by its "bandit's mask" across the eyes. It is generally brownish and may have a white stripe down its back. The hind legs are usually striped as well.
The belly is white although it may have some mottling. In general, the skin is quite smooth, but there may be some small warts along the sides. The dorsolateral ridges are also quite prominent, but they are not light-coloured. Sometimes the wood frog is confused with immature spotted or northern leopard frogs. Although the spotted frog can have a faint mask, its belly is reddish, whereas the wood frog's belly is white. The northern leopard frog can be easily identified by its lightcoloured dorsolateral folds and its large dark spots with a lightcoloured ring around them.
Natural History
As its name suggest, the wood frog is forest-dwelling and it is often found in damp, shady woods. It is very cold-tolerant and it is found farther north than any other amphibian in the Western Hemisphere. It is often found far from water and it is quite active in hunting for food. It eats mainly worms and insects. In winter, it hibernates on land beneath leaf litter. The wood frog is currently on the Green List in the Status of Alberta Wildlife and is considered not to be at risk. Populations are healthy and widespread.
Breeding
Depending upon snowmelt, breeding can take place from late April to June. Males are quite vocal night or day during the short one- to two-week breeding period. The wood frog's call sounds like the quacking of a duck. Breeding ponds tend to be shallow, clear permanent or temporary ponds. Females will lay 2000 - 3000 eggs in large round masses of jelly. Each egg is roughly 1.5 mm in diameter and will hatch in three weeks or a little more, depending upon water temperature.
Larvae
Tadpoles will grow from 7-10 mm to 50 mm during their development. They are brown or dark green with a whitish underside, sometimes with a pink tinge. In 6-12 weeks, the tadpoles will transform into froglets, depending upon the temperature of the water.
DistributionThe wood frog is found throughout the aspen parkland and the boreal forest. It can live at elevations up to 2500 m although it is absent from many areas in the Rockies. It is widely found from northern B.C. to Quebec. Because of its cold-tolerance it is the only amphibian in North America found above the Arctic Circle. MonitoringBecause wood frogs live in moist shaded areas, they can be difficult to locate outside of the breeding season. In the spring, adults congregate at breeding ponds and begin calling. |
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