Ascaphus truei


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Ascaphus truei
Species Authority: Stejneger, 1899
Common Name(s):
English American Discoglossoid Toad, Bell's Toad, American Ribbed Toad, American Bell Toad, Coastal Tailed Frog, Pacific Tailed Frog, Tailed Frog

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2004
Date Assessed: 2004-04-30
Needs updating
Assessor(s): Geoffrey Hammerson, Michael Adams
Reviewer(s): Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

Geographic Range [top]

Range Description: This species ranges from the Cascades and the Pacific Coast from southern British Columbia, Canada south to north-western California, USA (Stebbins 1985, Nielson et al. 2001).
Canada; United States
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 likely 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.
Population Trend: Unknown

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

Threats [top]

Major Threat(s): It is sensitive to logging and road building (Leonard et al. 1993). Logging and construction practices that increase water temperatures and siltation might have an adverse effect on tailed frog 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: Range includes many national parks and wilderness areas. Maintenance of cool, forested, unsilted streams and stream corridors is a basic conservation need.

Citation: Geoffrey Hammerson, Michael Adams 2004. Ascaphus truei. The IUCN Red List of Threatened Species. Version 2015.2. <>. Downloaded on 29 August 2015.
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