The Wood Frog: Breeding

In early spring, as the ice begins to melt off of the ponds, wetlands are transformed from a quiet and still environment to a cacophony of duck-like calls. However, these are no ducks. The "quacking" that can be heard in early spring in northeastern US woodlands is the breeding call of the Wood Frog, Rana sylvatica.

In early spring these frogs will have just come from a winter spent frozen solid under the leaf litter of the forest floor. These frogs have a special type of "anti-freeze" in their blood that controls how ice crystals form in their bodies, preventing their cells from bursting. If you happen to stumble across one of these guys in the winter, their rock solid appearance may lead you to believe they were an unfortunate victim of old man winter. But after some time in a warm environment, you can witness the miraculous transformation of the frog thawing and returning to "life".

Wood frogs beat all the other frogs to the breeding ponds, and if you are not listening carefully, you just might miss the intense breeding season. I have spent nights at ponds where the "quacking" was so intense you'd think there weren't enough frogs in the forest to make such a racket. You could return to the same pond a week later and it would once again be quiet.

Upon close inspection the egg masses left behind by the frogs become obvious. Attached to any surface, they appear as large gelatinous masses that can appear to dominate the underwater landscape. Look closely and you may also find some of the casualties of the intense breeding season. Female wood frogs are larger than the males, and weighed down with eggs when they arrive at the pond. Male Wood frogs are very aggressive, often grabbing any frog in sight, even other species. When they find a female they will attempt to mate, regardless of whether other males are already in position. A female caught in the middle of such a "mating ball" can be crushed to death, drown, or fatally "burst" their abdominal cavity. The latter was the case for the female in the photo. The eggs in this case were not viable and never developed into tadpoles.

The frogs that do survive leave the eggs behind to whatever fate awaits them. The tadpoles that hatch develop quickly. If they don't the pond might dry up or they may face competition from other tadpole species. At first they feed on the jelly-like part of the egg mass, and can often appear to be "swarming" around the mass. They will also eat algae and other particles in the water. Eventually they will leave the water and make their way into the forest, returning to the pond only to join the intense mating game in the early spring.