Wood Frog

IUCN Red List

LC - Least Concern

NatureServe

N5 - Secure
S5 - Secure

Minnesota

not listed

Wood Frog is an easily recognized, medium-sized, terrestrial frog. It is 1½″ to 3¼″ long at maturity. Females are much larger than males.

The back (dorsal surface) is smooth to moderately rough. Prominent folds on each side of the back (dorsolateral) extend from the head to near the vent. The folds are light on top, dark on the sides. There are often additional short folds on the back between the dorsolateral folds.

The color varies. It is usually tan or brown, sometimes gray, reddish-brown, or yellowish-green. Females are usually more reddish than males. The back and sides may have dark mottling.

The belly (venter) is white, yellowish-white, or greenish-white and often has dark mottling on the throat and breast. There is a prominent dark mark on each side of the chest near the forelegs (pectoral region).

A prominent dark face mask extends from the snout to just behind the ear covering (tympanum). The tympanum is smaller than the eye. The upper lip is white.

The back legs have horizontal bands that may be dark or faint. The feet are webbed. On the fourth toe two or three joints are free of the webbing. Males have larger “thumbs” and stouter forelegs.

Size

Total length: 1¼″ to 2⅜″

Voice

Amphibian Research and Monitoring Initiative (ARMI), Midwest Region

Frog and Toad Calls

A short croak repeated several times. Often compared to the quacking of a duck.

Similar Species

The prominent dark face mask, often referred to as a robber’s mask, on a brown frog is a unique identifying characteristic. No other species is similar in overall appearance.

Moist wooded areas, ponds in woods and prairies.

Behavior

Wood frogs are territorial. Territory size is usually about 100 square meters.

Summer months are spent in moist woods or wooded swamps, bogs or ravines. In late fall the frogs migrate to nearby upland areas to find a site to overwinter.

Lifespan

3 to 4 years

Life Cycle

Breeding is explosive. It occurs from late March to late April after the first warm spring rains, often before ice is completely off the pond. Males do not defend territories at this time but frantically swim after and grab other individuals hoping to find a receptive female.

After breeding, the female will deposit 300 to 1,000 eggs in a mass (clutch) loosely attached to emergent vegetation usually near the clutches of other females. Communal egg laying is thought to raise the temperature of the of the communal mass promoting faster development and to protect the inner eggs from leeches and other predators. Metamorphosis occurs at 65 to 130 days. The tadpole is 2¾″ to 2⅜″ long preceding metamorphosis.

Adults overwinter under the shelter of a log, rock, bark, or leaf litter. They are freeze tolerant and can survive multiple freeze-thaw cycles. Glycerine is produced preventing the formation of ice crystals in vital organs.

Males typically live 3 years, females 4 years.

Tadpole Food

Algae, decaying organic matter, eggs and embryos of some salamanders

Adult Food

Spiders, beetles, bugs, moth larvae, slugs, snails, and other insects and small invertebrates.