Geographic Range: The wood frog, Rana sylvatica, is found from northern Georgia and in isloated colonies in the central highlands in the eastern to central parts of Alabama, up through the northeastern United States, and all the way across Canada into Alaska. It is found farther north than any other North American reptile or amphibian. It is the only frog found north of the Arctic Circle.

Habitat: Restricted to fairly large tracts of mesic coniferous, mixed, or deciduous forest where vernal pools are present.

Physical Description: Wood Frogs are medium-sized brownish frogs with a dark brown “mask” extending back through the eye and the tympanum to the shoulder, a dark stripe extending forward from the eye to the snout, and a white stripe extending along the upper lip. The ground color varies from grayish-brown, bronze, reddish-brown, to tan. Wood Frogs are usually unmarked dorsally except for some dark spots along the dorsolateral fold and on the sides and dark bands on the upper legs.

Diet: Wood frogs eat a variety of insects and other small invertebrates, especially spiders, beetles, bugs, moth larvae, slugs and snails.

Reproduction: The breeding season is protracted (usually lasting only a week or two) and early. Migration by males to the breeding pools typically takes place in late March to early April following the first warm days of spring. Wood Frogs are often in migration when there is still snow on the ground. Females lay eggs in large globular masses, usually attached to a submerged plant stem or twig near the water's surface. Tadpoles develop quickly, usually transforming in May and June.

Eggs: Wood Frog eggs are laid in a large, gelatinous structure containing 500–3,000 eggs and attached near the surface to a submerged substrate. The mass is initially clear or grayish in color, but may turn greenish from the growth of algae.

Larvae: Wood Frog tadpoles reach up to 4.8 cm in length and are plump with a short, high tail fin. The groundcolor is brownish or olive brown with gold and black speckles. The tail fin is usually lighter and blotched with black. The belly is irredescent white or bronze, and the intestinal coil is visible through the skin.

The wood frog is an Obligate Species and must live or breed in vernal pools.

Natural History: Wood Frogs are less aquatic than the other species of Ranids, usually only congregating around water during breeding—for the rest of the year Wood Frogs are solitary woodland animals. They hibernate on land under loose soil, leaf litter, or in decaying logs. Wood frogs are known to undergo a form of cryogenics (freezing) during winter and survive till spring when they thaw out. Their diet consists of terrestrial invertebrates such as beetles, crickets, earthworms, slugs, and spiders. Juveniles may eat a larger percentage of aquatic invertebrates, while tadpoles eat algea, diatoms, and decaying plant and animal matter. They may at times consume larvae and eggs of other amphibians.

Vernal Pool Conservation

What you can do:

• Resist the temptation to clean up in and around vernal pool habitats. Leave trees, bushes, and understory vegetation, as well as brush, logs, and dead trees.
• Leave a buffer of natural vegetation around the pool for as great a distance as possible back from the edge of the pool's high-water mark. A buffer of at least 100 feet will help maintain water quality, but will do little to protect amphibians living around the pool. Vernal pool breeders require at least 300 yards of natural habitat around their pools in order to survive.
• Do not fill in the pool, even when it is dry, by dumping leaves or other debris in it.
• In areas with more than one pool, try to maintain travel corridors of natural vegetation between them. If some clearing is necessary, avoid drastic alterations that remove most of the trees and other cover. If habitat alterations are necessary, conduct these activities between November and March, when amphibians are less likely to be present. Activities done when the ground is frozen will cause much less damage to the soil than those conducted during warmer months.
• Avoid activities that inadvertently alter the movement of surface water (hydrology) of the upland area that drains into the pool. Digging ditches and similar activities can change runoff into the pool, thereby altering its flooding cycle.
• Do not dig into the bottom of the pool, even when it is dry, as this will disturb the non-permeable layer of soil that allows the pool to flood.
• Work with local conservation commissions and other interested individuals to identify and document vernal pools in your area.

  *Adapted from the Audubon Society of New Hampshire and the Nongame and Endangered Wildlife Program of the New Hampshire Fish and Game Department.

Photo by Tom Lautzenheiser.

A vernal pool is a temporary or semi-permanent body of water, typically filled in the spring by snow melt and spring rain, and holding water for two or three months in the spring and summer.

Vernal pools form in contained basin depressions, meaning that while they may have an inlet, they have no permanent outlet forming a downstream connection to other aquatic systems. They are typically small, rarely exceeding 50 m in width, and are usually shallow. While most are filled with meltwater and spring rains, others may be filled during the fall or with a combination of seasonal surface runoff and intersection with seasonally high groundwater tables. Typical substrates are formed primarily of dense leaf litter. While most vernal pools are found in upland forest, several types have been identified, including floodplain basins, swamp pools and marsh pools.

Periodic drying is a key feature of the ecology of vernal pools. Drying precludes the establishment of permanent fish populations, which would otherwise act as predators on the eggs and larvae of species that live or breed in the pool. While a typical vernal pool is dry during at least part of the year, others may contain some water throughout the year (or for several years), but a combination of shallow water, summer heat, winter freezing, and periodic oxygen depletion prevent the establishment of fish populations.

Terms:

Obligate Species: Species must live or breed in vernal pools.
Facultative Species: Species may be found in vernal pools, but can reproduce in other aquatic habitats where they are available.
Dorsolateral ridge: Lines or folds of skin (usually gold colored) along the upper sides of some frogs in the family Ranidae.
Intercalary cartilage: An extra piece of cartilage in the toes of members of the Hylidae (tree frog) family. It causes the end of the toes to have a “stepped-down” appearance.
Parotoid glands: Large skin glands that appear as swellings on each side of the back of the head of toads (family Bufonidae) and some salamanders.
Tympanum: This is the external ear drum visible on the side of the head of most frogs.

Kiehl, K. 2000. "Rana sylvatica" (On-line), Animal Diversity Web
Accessed March 31, 2004 at https://animaldiversity.ummz.umich.edu/site/accounts/information/Rana_sylvatica.html

The Roger Tory Peterson Institute is a national, non-profit nature education organization with headquarters in Jamestown, New York, birthplace of world renowned artist and naturalist, Roger Tory Peterson (1908-1996). In collaboration with the Center for Applied Technologies in Education, the Roger Tory Peterson Institute has provided these animal profiles to offer a glimpse into the diversity of Vernal Pools in our region.