Rana sylvatica
(Wood Frog)

Key Characteristics:

Adult Characteristics

Tadpole Characteristics

Egg Characteristics

Dark eye mask

Eyes inset


Dorsolateral fold

Long tail

Small spherical

Light stripe
on upper lip

Short snout


Webbing not to
ends of toes

Cream ventrally
with pinkish tinge


Males call

    .      .

General Description:
Wood Frogs are small to medium sized frogs reaching sizes of around 50mm (2 in.).  They vary in coloration, but are generally some shade of brown, green or gray.  Wood Frogs have a white ventral coloration with dark mottling near the chest and throat.  A characteristic marking on Wood Frogs is the dark stripe extending from the nose, through the eye and past the tympanum.  This dark stripe is contrasted by a light stripe along the upper lip.  Wood Frogs have prominent dorsolateral folds and relatively short hind legs.  The hind feet do not have webbing to the ends of the toes.  Males will produce a call that has been described as being similar to the quacking of small ducklings (Nussbaum et al. 1983).

Wood Frog tadpoles have a  brown or olive color dorsally, and have a light, pinkish-tinged ventral coloration.  Tadpoles can reach sizes of around 50mm (2 in.) prior to metamorphosing.  Like other Ranid tadpoles, the eyes of Wood Frog tadpoles are set in from the margin of the head.  Wood Frog tadpoles have tails that are nearly twice their body length.

Wood Frog eggs are 2mm (1/12 in.) in diameter and they are pigmented.  The egg masses are spherical containing up to 3000 per clutch.   As with the Columbia Spotted Frog, multiple females may lay eggs at the same location.  This species is an explosive breeder, and most breeding activity will occur over just a few days time.

Idaho Distribution:
Wood Frogs are rare in Idaho. They have only been found in the two northernmost counties of Idaho (Nussbaum et al. 1983).

From northern Alaska, east to Labrador, and south to New Jersey, Georgia, and northern Idaho; spotty distribution occurs south in Rocky Mountains to northern Colorado. Disjunct populations exist in Arkansas and Missouri. Only amphibian in North America to occur north of Arctic Circle.

In the western portion of their range, Wood Frogs are generally associated with more open wooded areas or meadows.  They breed in permanent water such as ponds or lakes and then return to the surrounding area to forage.  These frogs hibernate terrestrially under forest debris and in the soil.

Found in various kinds of forest/woodland habitats, including edges of ponds and streams, willow thickets, and grass/willow/aspen associations.

Unstudied in the Northwest, but at other locales, metamorphosed frogs eat various small invertebrates (mostly terrestrial forms). Larvae eat algae, plant tissue, organic debris, and minute water-borne organisms.

Hibernates/aestivates. Scant life history information exists for the Northwest. Inactive during cold season in north and at high elevations. When inactive, hides in humus, leaf litter, under rocks, or in/under logs. Primarily diurnal in northwestern range and in spring at high elevations, although breeding activity may occur at night. Most active in summer in damp conditions. After leaving pond, usually remains in an area less than 100 m across. Aquatic insect and shrew predators are repulsed by wood frog skin secretions. Population status and distribution in Idaho are unknown, but species has not been collected since early 1980's.

Females lay eggs in winter through early June, depending on range (in Idaho, known to breed early and move to breeding waters before ice is off ponds). Larvae metamorphose in spring or summer, depending on locality. Period from fertilization to emigration from pond averages about 11-16 wk, depending on range. Adults become sexually mature in 2-3 yr.



Unprotected nongame species

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Species description, key characteristics and original work by John Cossel Jr. © 1997
Species ecological information from Groves et al. ©1997.
Original images provided by Charlotte Corkran and Larry West © 1997
Design and Optimization by Ean Harker©1999, 2000.
DAI layout by Stephen Burton, and Mike Legler © 1999.