AmphibiaWeb - Ascaphus truei


(Translations may not be accurate.)

Ascaphus truei Stejneger, 1899
Pacific Tailed Frog, Coastal Tailed Frog, Western Tailed Frog
family: Ascaphidae
genus: Ascaphus
Species Description: Stejneger, L. 1899. Description of a new genus and species of discoglossoid toad from North America. Proceedings of the United States National Museum 21: 899.901.
Ascaphus truei
© 2017 Heidi Rockney (1 of 99)
Conservation Status (definitions)
IUCN Red List Status Account Least Concern (LC)
NatureServe Use NatureServe Explorer to see status.
National Status None
Regional Status California: Protected, and a Species of Special Concern
conservation needs Access Conservation Needs Assessment Report .


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Dorsal coloration variable; ground color may be cream, grey, red, or black. Dorsum may show a variable pattern of dark streaks and blotches. Head lacks tympanum, pupil is vertical, and a light streak may extend from tip of snout to above the eyes. Whitish-yellow venter, more yellow in femoral region. Males have a tail-like extension of the cloaca, and during breeding season show greatly enlarged forearms. Larvae have a distinctively large, round mouth, modified for suction, which they use to cling to streamside rocks (modified from Stebbins 1951).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Canada, United States

U.S. state distribution from AmphibiaWeb's database: California, Oregon, Washington

Canadian province distribution from AmphibiaWeb's database: British Columbia

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View distribution map in BerkeleyMapper.
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From sea level to timberline, ranging along Pacific coast of North America from northern California to southern British Columbia. Also includes a disjuct distribution in northern Idaho and western Montana (Nussbaum et al 1983). Associated with cold, fast-moving streams with cobbled bottoms and emergent boulders (Bull and Carter 1996).

Life History, Abundance, Activity, and Special Behaviors
Ascaphus is non-vocal. Its internal fertilization (an adaption to ensure fertilization in fast moving streams) is unique among frogs. Breeding season lasts from May through September. Eggs are deposited in strings under rocks in fast-moving streams. Tailed frogs are primarily aquatic; adults may emerge to forage on land in cool, wet conditions, especially at night. Larvae take between 1 to 4 years to metamorphose, depending on drainage (Bull and Carter 1996; Wallace and Diller 1998) . Juveniles are sexually mature in 7-8 years. Maximum average Ascaphusdensity per linear meter of stream was 0.162 larvae and 0.035 adults in western Oregon (Bull and Carter 1996). Nussbaum et al (1983) cite densities as high as 1 frog per meter of stream in eastern Washington.

Trends and Threats
Not federally listed, but a California Species of Special concern. Habitat modification due to timber harvesting may be a major cause of declines in Ascaphus. Bull and Carter (1996) found that the presence of a tree-lined buffer zone was significantly correlated with Tailed frog abundance, while overall logging level within the watershed showed only a non-significant trend. In British Columbia, conservation plans are difficult to implement, since Tailed Frogs (along with Pacific Giant Salamanders, Dicamptodon tenebrosus) avoid areas with predatory game fish; it is the riparian areas with those game fish that are protected (Orchard 1992).

Possible reasons for amphibian decline

Habitat modification from deforestation, or logging related activities

Ascaphus is the only living representative of a basal lineage of anurans, and may retain some relatively primitive traits of early frogs (e.g. Ford and Cannatella 1992).

See another account at


Bull, E. L. and Carter, B. E. (1996). ''Tailed Frogs: Distribution, ecology, and association with timber harvest in Northeastern Oregon.'' United States Forest Service Research Paper, (497), 1-12.

Ford, L.S., and Cannatella, D.C. (1993). "The major clades of frogs." Herpetological Monographs, 7, 94-117. [link]

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

Orchard, S.A. (1992). ''Amphibian population declines in British Columbia.'' Declines in Canadian amphibian populations: designing a national monitoring strategy. C. A. Bishop nd K.E. Petit, eds., Canadian Wildlife Service, 10-13.

Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.

Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.

Wallace, R. L. and Diller, L. V. (1998). ''Length of the larval cycle of Ascaphus truei in coastal streams of the redwood region, northern California.'' Journal of Herpetology, 32(3), 404-409.

Originally submitted by: Alan Krakauer, Meredith J. Mahoney (first posted 1999-02-16)
Distribution by: Michelle S. Koo (updated 2021-03-17)

Edited by: Duncan Parks and Meredith J. Mahoney (2021-03-17)

Species Account Citation: AmphibiaWeb 2021 Ascaphus truei: Pacific Tailed Frog <> University of California, Berkeley, CA, USA. Accessed Jul 16, 2024.

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Citation: AmphibiaWeb. 2024. <> University of California, Berkeley, CA, USA. Accessed 16 Jul 2024.

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