Wood Frog Ecology

Adults and Breeding

Wood frogs have a short breeding season (one to two weeks) typically beginning in late March to early April following several consecutive warm days—there may be snow still on the ground and patches of ice on the water when adults migrate to their breeding pools. They are easiest to detect during this period when males are in chorus, as a full chorus is loud and unmistakable. Males make a clucking sound that collectively—and from a distance—sounds like a flock of ducks quacking. Observation of amplexus is evidence that Wood Frogs are breeding in your pool: during amplexus, the male uses his forelegs to grasp the female from above so that he might fertilize her eggs externally as they are laid. The pair usually moves into deeper water where the female may release between 500 and 3,000 eggs.

Eggs

Choruses and amplexus both take place at night, however. An easier method for establishing Wood Frog breeding is to examine the pool for egg masses. Each female Wood Frog will produce a single egg mass, and several hundred females may lay their eggs in a single “nesting site” within the pool. Wood Frog eggs are black and surrounded by a clear jelly: a single egg mass may contain hundreds or thousands of eggs clumped together in a rounded gelatinous ball about the size of a fist. Older egg masses may turn greenish from symbiotic algae. The mass of eggs is attached to a branch, rush, or some other submerged vegetation, and is usually positioned so that it can float near the surface but in water deep enough that it won’t become exposed as the pool’s water level drops. Large numbers of floating egg masses can give the water’s surface a bubbly appearance.

Tadpoles

The incubation period is temperature-dependant, lasting anywhere from four days to four weeks. Eggs typically begin to hatch in mid- to late-April. Tadpoles are ready to transform in six to fifteen weeks. For the first several days after hatching the larvae remain in the sun attached to the vegetation near the spent egg mass and appear as greenish-black “apostrophes.” By May the tadpoles are much larger—reaching up to 4.8 cm in length—and are brown or olive, sometimes speckled with black and gold, with a short, high tail fin and an iridescent whitish or bronze belly. By late May, they may share the pool with tadpoles of toads and other frogs. Without experience distinguishing between the various tadpoles may be difficult, so it is best to look for Wood Frog tadpoles no later than early May. The greenish, filmy spent egg masses may remain visible in the pool through April.