TAILED FROGS: Ascaphidae

PHYSICAL CHARACTERISTICS

The tailed frogs get their name from their "tails," but only the males have them and they are not really tails at all. The tiny nub of a "tail" is really a fleshy structure that the adult male uses to mate with a female. Besides the "tails," the males and females look alike. Both have wide heads and large eyes with vertical, often diamond-shaped pupils. Unlike many other frogs, they have no round patch of an eardrum showing on the sides of the head. The skin of the tailed frog's back is covered with little warts, giving it a grainy look.

The frogs are usually shades of brown or gray, sometimes with a hint of green or red, and have darker markings, including blotches on the back and bands on all four legs. A lighter-colored patch, usually outlined with a thin, dark stripe, stretches between the eyes. Once in a while, a tailed frog may be almost completely black. The underside is pink, sometimes speckled with white. Tailed frogs have slender forelegs with no webbing on the toes and larger hind legs with well-webbed toes. Their toes, especially the outside toe on each foot, are quite wide.

Adult tailed frogs are small, growing only to 1.2 to 2.0 inches (3 to 5 centimeters) long from the tip of the snout to the end of the rump. The females are a bit bigger than the males. The tailed frog tadpole is dark gray and has a large, telltale sucker on the bottom of its broad head. Like other frogs, the tadpole has a long tail. When it begins to change into a frog, the tail shrinks until it disappears altogether. Often, people see an adult male tailed frog and believe that it is just a froglet that still has some of its tadpole tail left. This is not correct. The fleshy nub on an adult male tailed frog is different from a tadpole tail and never disappears.

Two species of tailed frogs exist: the Rocky Mountain tailed frog and the coastal tailed frog. They look so much alike that scientists thought they were the same species until 2001 when they compared the frogs' DNA. DNA, which is inside the cells of all animals, is a chain of chemical molecules that carry the instructions for creating each species and each individual. In other words, DNA is a chemical instruction manual for "building" a frog. The DNA of the Rocky Mountain tailed frog and the coastal tailed frog were just different enough to separate them into two species.

Both of these frog species have very small lungs, compared to most other frogs, and have extra backbones. Only one other living group of frogs, the New Zealand frogs, has the same extra backbones. Scientists have found fossil frogs far in the past that had the extra bones. These date back to the dinosaur age 150 million years ago and are the oldest known frogs.

GEOGRAPHIC RANGE

Both species live in North America. The coastal tailed frog lives along the Pacific Ocean coastline from northern California in the United States into British Columbia in Canada, but not on Canada's Vancouver Island. The Rocky Mountain tailed frog makes its home in Idaho, western Montana, southeastern Washington, northeastern Oregon, and the most southeastern portion of British Columbia.

HABITAT

These frogs are found in or near clear, rocky, swift-moving streams that flow through forests. When they are in the fast current, they breathe mainly through their skin and do not have to rely on their lungs as much. Human beings get their oxygen by breathing air into the lungs. There, blood picks up the oxygen out of the air and delivers it through blood vessels to the rest of the body. Frogs can get their oxygen from the water. Water, also known as H₂O, is made up of two chemicals: hydrogen and oxygen. (The H₂ means two atoms of hydrogen are in every molecule of water, and the O means one atom of oxygen is in each molecule.) The water runs past the frog, and blood vessels near the surface of its skin take up the oxygen from the flow. This arrangement allows the frog to survive even though it has very small lungs. On land, the frogs continue to breathe through the skin, which they must keep moist, but they are also able to take up some oxygen from the air through their lungs, as people do.

DIET

Adult tailed frogs eat insects, snails, and other invertebrates (in-VER-teh-brehts), which are animals without backbones, that they find either in the water or on land nearby. Tailed frogs do not have long tongues that flip far out of their mouths to nab prey. Rather, they have short tongues that are of little use for catching passing invertebrates. They are able to capture prey by remaining still and waiting for an insect or other prey animal to come just close enough that the frog can quickly jump out and grab the insect with its mouth. Tadpoles get their food another way. Tadpoles use the strong sucker around the mouth to cling to underwater rocks and avoid being swept away by the current. While they are hanging on, they scrape up and eat bits of algae (AL-jee) with their rows of tiny teeth. Algae are tiny plantlike organisms that live in water and lack true roots, leaves, and stems.

BEHAVIOR AND REPRODUCTION

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.

PIGGYBACK PADS

Many male frogs, including the tailed frogs, have rough pads on the soles of their front feet that they use during mating season. In the case of the tailed frogs, the pads are black, but they can be other colors, too. Called nuptial (NUHP-shul) pads, they help the males grab hold of the female's often slippery body during mating. This grip, in which the male looks as if he is taking a piggyback ride on the female's back, is called amplexus (am-PLEK-sus). Depending on the species, the male may hold onto the female up by her forelegs, a position that is called axial (ACK-see-uhl) amplexus, while the male of other species, including the tailed frog, may hang on in front of her hind legs in a position called inguinal (ING-gwuh-nuhl) amplexus.

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.

TAILED FROGS AND PEOPLE

People are often not aware of these quiet, little nighttime frogs, and believe they are very rare. However, they are actually quite plentiful in their habitat.

CONSERVATION STATUS

Neither species is considered to be at risk. Conservationists continue to keep watch over the frogs, however, because they must have clean and clear streams to survive. Human activity, such as logging or nearby housing development, can cause dirt and other things to wash into the frogs' streams, making the water too muddy or too polluted for the frogs to survive. Organizations in Canada, in particular, have begun protecting the habitat of this frog.

ROCKY MOUNTAIN TAILED FROG (Ascaphus montanus): SPECIES ACCOUNT

Physical characteristics: The Rocky Mountain tailed frog is a medium-sized brown to brownish black, sometimes gray, frog with tiny black specks. A lighter brown patch spreads between the large eyes, often dipping down toward the rounded snout. Its belly is pink. The male has a small nub of a "tail," which is actually not a real tail at all. It looks almost identical to the coastal tailed frog, except that the Rocky Mountain species has a bit more webbing between the toes of its hind feet and its tadpoles do not have the white-spotted tail tip that many of the coastal species' tadpoles do. Adults of both the Rocky Mountain tailed frog and the coastal species usually grow to 1.2 to 2.0 inches (30 to 50 millimeters) long from snout to rump.

Geographic range: This species is found in the northwestern United States, including Idaho, Montana, Oregon, and Washington and in British Columbia in Canada.

Habitat: Rocky Mountain tailed frogs live in mountain forests near and often in small, clear, rocky-bottomed streams with fast currents.

Diet: They eat insects and other invertebrates they catch in the water or on land nearby. They look for food at night. Tadpoles are vegetarians and use their small teeth to scrape algae (AL-jee), or microscopic plantlike organisms, off underwater rocks.

Behavior and reproduction: Active mainly at night, they spend their days hidden under rocks along the shoreline. They mate in the fall, and each female lays 45 to 75 eggs in the water the following summer. The eggs hatch into tadpoles, which may remain in that state for up to five years. Finally, the tadpoles turn into froglets, and another seven or eight years later, they are adults. In the wild, the frogs may live to be 15 to 20 years old.

Rocky Mountain tailed frogs and people: Scientists find both species of tailed frogs interesting because they have some features of the earliest known frogs that hopped the Earth at the time of the dinosaurs, and they mate differently from most other frogs alive today.

Conservation status: The Rocky Mountain tailed frog is not considered to be at risk. The Committee on the Status of Endangered Wildlife in Canada, however, lists it as Endangered, which means that it may soon disappear. Organizations in British Columbia have begun protecting the frog's habitat, including land in the Wycliffe Wildlife Corridor in the Kootenay region of British Columbia. ∎

FOR MORE INFORMATION

Books:

Corkran, Charlotte. Amphibians of Oregon, Washington, and British Columbia. Auburn, WA: Lone Pine Publishing, 1996.

Nussbaum, R. A., E. D. Brodie, and R. M. Storm. Amphibians and Reptiles of the Pacific Northwest. Moscow: University of Idaho Press, 1983.

Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians (Peterson Field Guide Series). Boston: Houghton Mifflin, 2003.

Wright, A. H., and A. A. Wright. Handbook of Frogs and Toads of the United States and Canada. Ithaca, NY: Comstock, 1949.

Web sites:

"I Only Have Eyes for You." All About Frogs.http://allaboutfrogs.org/weird/general/eyes.html (accessed on February 7, 2005).

Mierzwa, Ken. "In Search of Tailed Frogs." Ken Mierzwa.http://kmier.net/ecology/tailed.html (accessed on January 31, 2005).

"Rocky Mountain Tailed Frog." The Land Conservancy. http://www.conservancy.bc.ca/sectioncontent.php?sectionid=55&pageid=380 (accessed on January 31, 2005).

"Tailed Frog." Yahooligans Animals.http://yahooligans.yahoo.com/content/animals/species/4281.html (accessed on January 31, 2005).

Thompson, Don. "Frogs Provide Clues to Calif. Environment." Kansas City Star (Monday, November 10, 2003). http://www.kansascity.com/mld/kansascity/news/nation/7227129.htmMon, Nov. 10, 2003 (accessed on February 7, 2005).