Tailed Frogs: Ascaphidae

During the day, adult tailed frogs stay hidden in damp to wet spots under rocks along the streamside. At night, especially during or after a rain, they hop about on land near the stream to look for food. They still must keep their skin moist while they are out of the water, because dry skin prevents them from taking up oxygen from the air. They move about on land by hopping and in the streams by sweeping their strong hind feet as they swim through the water. When in the water, they tend to stay in areas where overhanging trees cast shadows. Newly hatched tadpoles, which are almost see-through compared to the darker, older tadpoles, remain in slower water, often in small side pools where the current is calmer. The larger tadpoles, however, brave the strong current by using their large suckers to attach tightly to rocks.

These small frogs mate in the fall. They do so quietly because male tailed frogs do not call, as the males of most other frog species do. During the breeding season, the males grow black pads on their front feet and small black bumps on their forelegs and along their sides. These pads and bumps help the male grab and hang onto the back of a female during mating. As in other frogs, the male tailed frog must add a fluid to the female's eggs so they will develop into tadpoles and frogs. This process is called fertilization (FUR-tih-lih-ZAY-shun). The eggs are actually fertilized by microscopic cells called sperm that float inside the male's fluid. In most frogs, the male adds his sperm-filled fluid to the eggs as the female lays them, so the mixing of the eggs and sperm cells happens outside her body. A male tailed frog, however, fertilizes the eggs differently. He swings his "tail" around, squeezes it into the hole in the female's body that she will use to lay her eggs, and releases the fluid inside her body instead of outside. The female then saves the fluid within her body until she is ready to lay her eggs the next summer. When she does lay them, her eggs are already fertilized. The type of fertilization that happens inside the female's body is called internal (in-TER-nuhl) fertilization. The other type of fertilization, which happens outside the body and is used by most other species of frogs, is called external (eks-TER-nuhl) fertilization.

A female tailed frog can lay 35 to 100 eggs at a time. She lays her eggs underwater, sticking them under rocks and usually in an area of the stream where the current is slower, so the eggs are not swept away downstream. The eggs hatch about six weeks later into small, colorless tadpoles, which soon develop the mouth suction cups and grow into larger, dark-colored tadpoles. They may remain tadpoles for five to seven years before they finally turn into small froglets. They usually switch from tadpole to froglet in the spring or summer. The froglets may need another 3 to 8 years before they are adults themselves. This is unusual. Most other species of frogs go from egg to tadpole to froglet to adult frog in a shorter amount of time, often within a single year. The tailed frogs not only take a much longer time to develop, but they also stick around longer overall. They often live in the wild to the ripe old age of 15 or 20 years, making them some of the longest-living frogs in the world. Through their long lives, tailed frogs remain near the spot in the stream where they were born.