Ascaphus truei 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Amphibia Anura Ascaphidae

Scientific Name: Ascaphus truei
Species Authority: Stejneger, 1899
Common Name(s):
English Coastal Tailed Frog, Bell's Toad, American Ribbed Toad, American Discoglossoid Toad, American Bell Toad, Pacific Tailed Frog, Tailed Frog
Taxonomic Source(s): Frost, D.R. 2013. Amphibian Species of the World: an Online Reference. Version 5.6 (9 January 2013). Electronic Database. American Museum of Natural History, New York, USA. Available at:

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2015
Date Assessed: 2015-08-25
Assessor(s): IUCN SSC Amphibian Specialist Group
Reviewer(s): Stuart, S.N.
Contributor(s): Hammerson, G.A. & Adams, M.
Facilitator/Compiler(s): Sharp, D. & Hobin, L.
Listed as Least Concern in view of the large extent of occurrence, large number of sub-populations and localities, and presumed large population size.
Previously published Red List assessments:
2004 Least Concern (LC)

Geographic Range [top]

Range Description: Range includes the Cascade Mountains and Pacific coastal areas of North America from west-central British Columbia, Canada, south to northwestern California, USA (Nielson et al. 2001, Stebbins 2003).
Countries occurrence:
Canada (British Columbia); United States (California, Oregon, Washington)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species has many extant occurrences distributed throughout the range. Total population size is unknown but probably exceeds 10,000. It is common in suitable habitat. Its long-term trend is probably relatively stable in terms of extent of occurrence. There has been an unknown degree of decline in population size, area of occupancy, and number/condition of locations. Its short-term population trend is probably declining based on habitat trends, but few population data are available.
Current Population Trend: Unknown
Additional data:
Population severely fragmented: No

Habitat and Ecology [top]

Habitat and Ecology: Can be found in clear, cold swift-moving mountain streams with coarse substrates. Primarily in older forest sites, required microclimatic and microhabitat conditions are more common in older forests (Welsh 1990). Diller and Wallace (1999) reported that canopy cover, temperature, and forest age in managed forests were not significantly different between occupied and unoccupied stream reaches in northern California; however, this probably reflects past timber harvest patterns. Animals may be found on land during wet weather near water in humid forests or in more open habitat. During dry weather it stays on moist stream-banks and lays eggs in long strings under stones in water.
Systems: Terrestrial; Freshwater

Use and Trade [top]

Use and Trade: There are no records of this species being utilized.

Threats [top]

Major Threat(s): It is sensitive to logging and road building (Leonard et al. 1993). In addition to clearing of habitat for road building, pollution resulting from road building is also a threat, which happens when sedimentation occurs as a result of poorly constructed roads. Logging and construction practices that increase water temperatures and siltation might have an adverse effect on tailed frog sub-populations (Nussbaum et al. 1983, Welsh and Ollivier 1998). See also Bury and Corn (1988) and Corn and Bury (1989) for information on negative effects of timber harvest. Diller and Wallace (1999) emphasized that current timber harvest practices are not as detrimental as those used in the past. Despite negative effects of logging, this species frequently occurs in many young forests that have been harvested one or more times in the past. Sensitivity to timber harvest might depend on surface geology and harvest practices (Adams and Bury 2002, Welsh and Lind 2002).

Conservation Actions [top]

Conservation Actions: Conservation Actions 
The species range includes many national parks and wilderness areas. 

Conservation Needed
Protection and management of cool, forested, unsilted streams and stream corridors is a basic conservation need.

Classifications [top]

1. Forest -> 1.4. Forest - Temperate
suitability: Suitable season: resident major importance:Yes
5. Wetlands (inland) -> 5.1. Wetlands (inland) - Permanent Rivers/Streams/Creeks (includes waterfalls)
suitability: Suitable season: resident major importance:Yes
1. Land/water protection -> 1.1. Site/area protection
1. Land/water protection -> 1.2. Resource & habitat protection

In-Place Research, Monitoring and Planning
In-Place Land/Water Protection and Management
  Occur in at least one PA:Yes
In-Place Species Management
In-Place Education
4. Transportation & service corridors -> 4.1. Roads & railroads
♦ timing: Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 2. Species Stresses -> 2.1. Species mortality

5. Biological resource use -> 5.3. Logging & wood harvesting -> 5.3.5. Motivation Unknown/Unrecorded
♦ timing: Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

9. Pollution -> 9.1. Domestic & urban waste water -> 9.1.2. Run-off
♦ timing: Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

Bibliography [top]

Adams, M.J. and Bury, R.B. 2002. The endemic headwater stream amphibians of the American Northwest: associations with environmental gradients in a large forested preserve. Global Ecology and Biogeography: 169-178.

Behler, J.L. and King, F.W. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York.

Blackburn, L., Nanjappa, P. and Lannoo, M.J. 2001. An Atlas of the Distribution of U.S. Amphibians. Ball State University, Muncie, IN, USA.

Bury, R.B. and Adams, M.J. 1999. Variation in age at metamorphosis across a latitudinal gradient for the tailed frog, Ascaphus truei. Herpetologica: 283-291.

Bury, R.B. and Corn, P.S. 1988. Responses of aquatic and streamside amphibians to timber harvest: a review. In: Raedaeke, K. (ed.), Streamside management: riparian wildlife and forestry interactions, pp. 165-181. Univ. Washington.

Corn, P.S. and Bury, R.B. 1989. Logging in western Oregon: responses of headwater habitats and stream amphibians. Forest Ecology and Management: 39-57.

Daugherty, C.H. and Sheldon, A.L. 1982. Age-determination, growth, and life history of a Montana population of the tailed frog (Ascaphus truei). Herpetologica: 461-468.

Daugherty, C.H. and Sheldon, A.L. 1982. Age-specific movement patterns of the frog Ascaphus truei. Herpetologica: 468-474.

Diller, L.V. and Wallace, R.L. 1999. Distribution and habitat of Ascaphus truei in streams in managed, young growth forests in north coastal California. Journal of Herpetology: 71-79.

Dupuis, L. 1998. Status report on the tailed frog, Ascaphus truei, in Canada (draft). Unpublished draft report submitted to the Commitee on the Status of Endangered Wildlife in Canada, Ottawa.

Dvornich, K.M., McAllister, K.R. and Aubry, K.B. 1997. Amphibians and reptiles of Washington State: Location data and predicted distributions, Vol. 2. In: Cassidy, K.M., Grue, C.E., Smith, M.R. and Dvornich, K.M. (eds), Washington State Gap Analysis - Final Report, Washington Cooperative Fish and Wildlife Research Unit, University of Washington, Seattle, Washington.

IUCN. 2015. The IUCN Red List of Threatened Species. Version 2015-4. Available at: (Accessed: 19 November 2015).

Leonard, W.P., Brown, H.A., Jones, L.L.C., McAllister, K.R. and Storm, R.M. 1993. Amphibians of Washington and Oregon. Seattle Audubon Society, Seattle, Washington.

Metter, D. and Pauken, R. 1969. An analysis of the reduction of gene flow in Ascaphus truei in the northwest U.S. since the Pleistocene. Copeia: 301-307.

Metter, D.E. 1968. Ascaphus and A. truei. Catalogue of American Amphibians and Reptiles: 1-2.

Nielson, M., Lohman, K. and Sullivan, J. 2001. Phylogeography of the tailed frog (Ascaphus truei): implications for the biogeography of the Pacific Northwest. Evolution: 147-160.

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

Ritland, K., Dupuis, L.A., Bunnell, F.L., Hung, W.L.Y. and Carlson, J.E. 2000. Phylogeography of the tailed frog (Ascaphus truei) in British Columbia. Canadian Journal of Zoology: 1749-1758.

Species at Risk Branch. 2002. Species at Risk Range Maps. Canadian Wildlife Service, Environment Canada. (, Ottawa.

Stebbins, R.C. 1985. A Field Guide to Western Reptiles and Amphibians. Second Edition. Houghton Mifflin Company, Boston, Massachusetts.

Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians, Third Edition. Houghton Mifflin Company, Boston, Massachusetts.

Thomas, J.W., Ward, J., Raphael, M.G., Anthony, R.G., Forsman, E.D., Gunderson, A.G., Holthausen, R.S., Marcot, B.G., Reeves, G.H., Sedell, J.R. and Solis, D.M. 1993. Viability assessments and management considerations for species associated with late-successional and old-growth forests of the Pacific Northwest. The report of the Scientific Analysis Team. USDA Forest Service, Spotted Owl EIS Team, pp. 530 pp. Portland, Oregon.

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: 404-409.

Welsh, H.H., Jr. 1990. Relictual amphibians and old-growth forests. Conservation Biology: 309-319.

Welsh, H.H., Jr. and Lind, A.J. 2002. Multiscale habitat relationships of stream amphibians in the Klamath-Siskiyou region of California and Oregon. Journal of Wildlife Management: 581-602.

Welsh, H.H., Jr., Hodgson, G.R. and Lind, A.J. 2005. Ecogeography of the herpetofauna of a northern Californian watershed: linking species patterns to landscape processes. Ecography: 521-536.

Citation: IUCN SSC Amphibian Specialist Group. 2015. Ascaphus truei. The IUCN Red List of Threatened Species 2015: e.T54414A78905810. . Downloaded on 25 November 2015.
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