Woodfrog
Rana sylvatica

Woodfrogs are among the first species of frogs in Ohio to migrate to breeding ponds and to begin calling. Several other species of ranid frogs, such as green frogs and leopard frogs, may emerge from hibernation as early as the woodfrog but do not begin calling. Adult frogs attain lengths of 47-61 mm with females averaging slightly longer. Males have paired vocal sacs, stout forearms, and swollen thumbs evident during the breeding season. Woodfrogs are dead leaf in color, brown to dark brown, with a black raccoon-like or robber mask across the face (Fig. 33). In the spring some females become orangish to brick red in color.

Fig. 33. Woodfrog

• Woodfrogs are brown to dead leaf in color with a black raccoon-like mask across the face. The dorsolateral folds are conspicuous and extend nearly to the groin.

The woodfrog is a terrestrial species occupying forests. It is found in ponds during the short breeding season, but thereafter the frogs disperse throughout the forests and lead solitary lives.

The woodfrog is an example of an explosive breeder, a species that congregates in large numbers at breeding ponds for a very short mating season lasting only two or three days to a week. They become active in mid-March and remain so until late October. Spawning is accomplished in small temporary pools, swamps, or semipermanent ponds and takes place from mid-March to early April in northeastern Ohio. Woodfrogs often lay their clutches of eggs aggregated in a central location of the pond thereby forming huge rafts of eggs deposited below the surface of the water. Individual egg masses are globular in shape and measure 75-100 mm in diameter. Each mass may contain 1000-5000 eggs with each egg swelling to 6-7 mm in diameter upon hydration. The eggs hatch in 14-21 days, and transformation occurs 61-115 days following spawning. Woodfrog tadpoles are dark, nearly black, and transform the year they hatch at lengths of 38-48 mm. Recently transformed woodfrogs 15-18 mm in length may be found from early June through late July. Sexual maturity is reached in two years.

The distributional range of the woodfrog extends farther north than that of any other North American species of amphibian and extends above the Arctic Circle in Alaska. They are most common and widely distributed throughout the eastern two-thirds of Ohio.

Calls of the woodfrog have little carrying power and sound similar to quacking ducks or clucking chickens (Fig. 34). The calls are frequently uttered in sequences of two to three as males spurt forward in the pond with two to three quick, successive kick-strokes.

	Fig. 34. Call of the woodfrog

Call of the woodfrog (50 seconds, 396 KB)
Excerpt (9 seconds, 77 KB)

• Calls of the woodfrog have little carrying power and sound similar to quacking ducks or clucking hens. Calls are frequently given in sequences of three as illustrated in the spectrogram.

• The dominant frequency of the call is about 1700 Hz, and the duration is 0.05 seconds.

• A chorus of spring peepers is evident in the distance in the audio clip.

Woodfrogs hibernate on land below the leaf litter and produce high concentrations of glucose (sugar) in the fall that protects their cells during freezing.