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Ministry of Environment

Tailed Frog

Present range of the Tailed Frog in British Columbia
Tailed Frog (Ascaphus truei)
Common Name:Pacific Tailed Frog
Rocky Mountain Tailed Frog
Scientific Name:Ascaphus truei
Ascaphus montanus
Status (B.C.):Blue (Pacific)
Red (Rocky Mountain)
Status (COSEWIC):Special Concern
(Rocky Mountain)


In 2000, the Tailed Frog was split into two species. The coastal species is Ascaphus truei, and is called the Pacific Tailed Frog. The Kootenay species is now called Ascaphus montanus, the Rocky Mountain Tailed Frog.

At a Glance

The Tailed Frog is a remarkable little frog, unique to B.C. in Canada. It is a small frog, 2.5 to 3 centimetres from nose to rump. Adults are usually tan or brown in colour although some may be shaded green or red, or even entirely black. The skin has a rather grainy appearance. Tailed Frogs have vertical pupils, no external tympanum (the round "ear" visible on other frogs), and are voiceless. The toes on the hind feet are flat and wide, especially the outer toes, and these can be used to distinguish Tailed Frogs from other frogs and toads.

The most remarkable feature of Tailed Frogs is the "tail" which gives the species its common name. The "tail," which only males have, is actually a copulatory organ used to fertilize the eggs of the female internally. While newly metamorphosed frogs of other species may have a remnant tail for a few days, it is a different colour from the body, while the "tail" of the Tailed Frog is the same colour and texture as the frog's back.

Unlike most frog species, the tadpoles of Tailed Frogs are easily identifiable, having a very large sucker-like mouth. Hatchlings are almost transparent, while older tadpoles are dark mottled brown or black, often with a white spot on the tip of the tail. Tailed Frog tadpoles are found clinging to stones in streambeds.

Home Sweet Home

The Tailed Frog likes clear, cool mountain streams. Small channels without fish and with shading plants and trees are favourite locations. The type of streambed is also important. Tailed Frogs are usually found in streams with large stones, cobbles, and stable boulders, which they can use for shelter from the rapid current. Some quieter side pools are also needed, so that eggs and hatchlings won't be washed away. The streams must contain water year round, since Tailed Frog tadpoles need to stay in the water for a long growth period. Adult Tailed Frogs often hide and hunt on the stream banks, but need to stay moist since they are much less able to withstand drying than other frogs.

Although young Tailed Frogs disperse from their hatching sites, once they reach adulthood they will usually not move far from their chosen stream. Home Sweet Home indeed!

This is the Life

Tailed Frogs grow very slowly, taking up to four years in high mountain populations for the tadpoles to metamorphose. It takes several more years for the froglets to become sexually mature. Tailed Frogs may live 15 to 20 years, making them one of the longest-lived frogs in the world.

Mating takes place in the fall, in streams, after a courtship ritual. Females mate only every second year. The male clasps the female and inserts his "tail" into the female's cloaca in order to inseminate her. She stores the sperm inside her body until the following summer, when she lays strings of eggs underwater, attaching them to the base of a large stone. Hatchlings emerge six weeks or so later, and overwinter in the quieter waters; they move out into the stronger current areas once their oral suckers have developed enough to let them cling to the rocks.

What’s on the Menu?

Tailed Frog tadpoles scrape algae from submerged rocks, and every once in a while will also swallow small insects and grains of pollen that fall into the water. Adult Tailed Frogs eat insects, snails and other small invertebrates, using a "sit and wait" strategy for hunting. The Tailed Frog is not able to grab prey with its sticky tongue as other frogs can - its tongue is attached closely to the floor of its mouth, so it cannot flip out its tongue to grab insects. Instead, the Tailed Frog must pounce on its prey and grab the meal with its mouth.

Where and When

Tailed Frogs are found from western B.C. south as far as California, and as far east as northwest Montana and Idaho. In B.C., they are found in the mountains on the coast and in small patches in the Kootenay. Clear, cold, swift headwater streams are the best places to look for Tailed Frogs. These frogs are found in or near their home streams year round.

How Are They Doing?

Tailed Frogs are vulnerable to human activities. Forestry activities and road building can damage breeding streams by removing cover vegetation, disturbing streambeds and contributing to siltation. Streams may become too warm for tadpoles if the shading trees are removed.

Pacific Tailed Frogs are relatively widespread in the coastal mountains. They have been placed on the provincial Blue List, and have been designated by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) as Special Concern. The Kootenay Tailed Frogs have a much smaller and more restricted range, and have been placed on the provincial Red List, and designated by COSEWIC as Endangered.

How We’re Helping

Tailed Frogs are protected from being killed, collected or harmed under the provincial Wildlife Act. Under the Identified Wildlife Management Strategy of the Forest Practices Code, Wildlife Habitat Areas can be established for critical breeding habitats. Scientists are studying the effects of forestry activities on the Tailed Frog.

How You Can Help

Adult Tailed Frogs are vulnerable to crushing if humans trample stream edges, overturning the stones that shelter the frogs. Tadpoles may be trampled or smothered by stirred-up silt if people or vehicles cross the streams. Accordingly, it is not a good idea to go out searching for them. However, if you do happen to come across Tailed Frogs, please notify B.C. Frogwatch or contact the Conservation Data Centre in Victoria.

You can also help by learning more about these frogs and about other amphibians, and by teaching others about them.

No Kidding!

  • The closest living relative of the Tailed Frog is a species found only in New Zealand
  • When hunting, these frogs "overshoot" their prey, gaping their mouths open as they pass the prey, then snapping it up as they recoil to a sitting position. The hind toes never leave the ground, while the front feet are held to the sides.
  • Tailed Frogs do not call. They have no eardrums, though they may be able to sense vibration in the water.

Photo © Wally Edwards. No reproduction or distribution without permission.