Species Profile: Coastal Tailed Frog

The Coastal Tailed Frog (Ascaphus truei) is very unique species whose range extends from northern BC to California. Tadpoles may grow to about 3 centimeters in length and may be greyish brown, reddish brown, and black in colour. Mature coastal tailed frogs grows to about 3 centimeters in length and may be light brown, greyish green, or charcoal with a grainy of pebbly skin texture. Another easy way to identify them, aside from the obvious tail, is by the vertical pupils, and a commonly found light tone bar or triangle shape between the eyes. In British Columbia, the Coastal Tailed Frog is Blue listed, and is considered of special concern by the Committee on the Status of Endangered Species in Canada (COSEWIC).

Coastal tailed frogs live within unique habitat conditions. They require fast-flowing cool water, and, due to their porous skin, require a very low sediment content. As such, extirpation has occurred in many urbanised areas due to stream heating from canopy loss, and increased sediment load due to storm water runoff. Adults are known to range up to 40 meters from streams; juveniles up to 100 meters.

Ascaphus truei is a very slow growing species, making it one of the worlds longest living frogs and at the same time susceptible to endangerment. The tadpole stage may last from 2 – 4 years long; sexual maturity may be reached within 8 – 9 years; and the overall life span may range from 15 – 20 years long! It is the only North American frog species to use internal fertilization. The “tail” is really a reproductive adaptation to the fast-flowing water in which it lives, and prevents the loss of sperm during mating. Breeding season is in the fall, and the following summer a female (who mates only once every two years) will attach a string of eggs to the underside of a river cobble or boulder.

The diet of a mature coastal tailed frog includes spiders, ticks, mites, and even snails. Another curious characteristic of this species is that it does not have the ability to extend its tongue. Rather, it uses a passive form of “sit-and-wait” hunting where it leaps and grabs nearby prey. Tadpoles are known to use their teeth to scrape algae off submerged rocks, as well as swallowing small insects and grains of pollen.

The tadpoles of this species display various environmental adaptations that allow them to survive in a dynamic natural environment. They are able to withstand the fast-flowing waters by using a suction-like mouth and their teeth to cling on to smooth cobbles . Tadpoles are also known to survive dewatering events, such as in ephemeral streams, by seeking refuge in the wet streambed material.

Nonetheless, the coastal tailed frog is threatened by anthropogenic stresses including habitat loss and fragmentation, microclimatic changes, storm water runoff, and waterborne contaminants. Unfortunately, this species is most commonly found in non-fish bearing streams and, as such, lacks the governmental protection that is awarded to other waterways.

A final tidbit of information: the coastal tailed frog is a silent species, with no ability to vocalise that characteristic “croak” associated with frogs. As such, tread carefully when in the riparian zone near streams and, as always, respect the delicacy of the nature you explore!

Check out some great photos highlighting the pebbly textured skin of the coastal tailed frog among our Flickr community group submissions here.

References:
BC FrogWatch Program
South Coast Conservation Program Factsheet

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