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Rocky Mountain Tailed Frog - Ascaphus montanus

Native Species

Global Rank: G4
State Rank: S4
(see State Rank Reason below)

Agency Status


External Links

State Rank Reason (see State Rank above)
Species is apparently secure and not at risk of extirpation or facing significant threats in all or most of its range.
  • Details on Status Ranking and Review
    Rocky Mountain Tailed Frog (Ascaphus montanus) Conservation Status Review
    Review Date = 05/03/2018
    View State Conservation Rank Criteria
    Range Extent

    ScoreF - 20,000-200,000 km squared (about 8,000-80,000 square miles)

    Comment70,521 square Kilometers from Natural Heritage Program range maps

    Long-term Trend

    ScoreE - Relatively Stable (±25% change)

    CommentAlthough forest management practices and fire regimes have changed over the last century it is unlikely that the amount of habitat for this species has changed more than 25%. Loss of old growth timber may have contributed to a reduction in suitable habitat, but the extent of the impact on this species is unknown.

    Short-term Trend

    ScoreU - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.

    CommentTo date surveys have not been conducted with enough frequency to determine trend


    ScoreG - Slightly threatened. Threats, while recognizable, are of low severity, or affecting only a small portion of the population or area.

    CommentDegradation of stream habitat through logging or wildfire

    SeverityLow - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.

    CommentGiven current forest management practices, impacts should not persist for more than 50 years

    ScopeLow - 5-20% of total population or area affected

    CommentSpecies is found across a large area so impact to large portions of the population would be unlikely

    ImmediacyLow - Threat is likely to be operational within 5-20 years.

    CommentPossible within the next 20 years, but is not imminent.

    Intrinsic Vulnerability

    ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).

    CommentThis species has high fecundity, a moderate age of maturity, and recruitment can be low.

    Environmental Specificity

    ScoreB - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.

    CommentSpecies is associated with montane streams within forested areas across western Montana.

    Raw Conservation Status Score

    Score 3.5 + 0 (geographic distribution) + 0 (environmental specificity) + 0 (long-term trend) + 0.75 (threats) = 4.25

General Description
Adults are gray or brown with gray, brown, or occasionally yellow blotches; the skin has a distinctly bumpy texture. Adult body length is 1.5 to 2 inches. The outer toe of the hind foot is broader than the other toes. Tailed frogs have no external ear drum. The male has a bulbous "tail" that acts as a penis. Eggs and Tadpoles: Approximately 50 eggs are laid in rosary-like strings attached to the underside of rocks. The tadpole (up to 2 inches long) is unique in that it has a large mouth modified into a sucker; color is variable.

Diagnostic Characteristics
No other frog or toad has the outer toe of the hind foot broader than the other toes; all other frogs and toads have external ear drums.

Species Range
Montana Range


Western Hemisphere Range


Observations in Montana Natural Heritage Program Database
Number of Observations: 2380

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Non-migratory. Has no breeding migration (Daugherty 1982).

Rocky Mountain Tailed Frogs are found in and along small, swift, cold mountain streams. Eggs are laid during late summer and take approximately 4 weeks to hatch. Tadpoles take 1 to 4 years to metamorphose, depending on water temperature. Sexual maturity in Montana is attained at 6 or 7 years of age (the latest of any North American amphibian). Forested streams. In Flathead area, larvae are found only in streams with temperature under 16 C. Prefer fast streams, less than 14 ft wide, with substrate of slabby-flat bottomed rocks with little aquatic vegetation (Franz and Lee 1970).

Food Habits
Larva feed almost exclusively on diatoms, though also pollen (Metter 1964, Franz 1970) Adults: opportunistic; forage at night in forest near streams. Prey on invertebrates, mainly terrestrial but also aquatic forms (Metter 1964, Bury 1970, Daugherty 1982).

Low reproductive potential: reproductive maturity age 7 to 8; 2 year cycle with first clutch at age 9 (Daugherty 1982). Extremely philopatric; probably very little gene flow between populations (Daugherty 1982).

Reproductive Characteristics
Mate August to September; sperm stored overwinter (Metter 1964). Ovipost late June to July; hatch August to September but remain in nest (under rocks in stream) until yolk is consumed, October to November or later. Metamorphose July to September of year 4 (ca. 60 days required) (Daugherty 1979). Development of eggs under natural conditions is discussed by Franz (1970).

  • Literature Cited AboveLegend:   View Online Publication
    • Bury, R.B. 1970. Food similarities in the tailed frog, Ascaphus truei, and the Olympic salamander, Rhyacotriton olympicus. Copeia 1970: 170-171.
    • Daugherty, C.H. and A.L. Sheldon. 1982a. Age-determination, growth, and life history of a Montana population of the tailed frog Ascaphus truei. Herpetologica 38(4): 461-468.
    • Franz, R. and D.S. Lee. 1970. The ecological and biogeographical distribution of the tailed frog, Ascaphus truei, in the Flathead River drainage of northwestern Montana. Bulletin of the Maryland Herpetological Society 6: 62-73.
    • Metter, D.E. 1964a. A morphological and ecological comparison of two populations of the tailed frog Ascaphus truei Stejneger. Copeia 1964: 181-195.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • [USFWS] US Fish and Wildlife Service. 1994. Endangered and threatened wildlife and plants; animal candidate review for listing as endangered or threatened species. Federal Register 59(219): 58982-59028.
    • Adams, M.J. 1993. Summer nests of the tailed frog (Ascaphus truei) from the Oregon coast range. Northwestern Naturalist 74: 15-18.
    • Adams, S. 1998. Tailed frog migration: a local response to seasonally unsuitable habitat? Abstract. Montana Chapter of the American Fisheries Society Meeting. Helena, MT. February 2-5, 1998.
    • Adams, S. and C.A. Frissell. 2001. Thermal habitat use and evidence of seasonal migration by Rocky Mountain tailed frogs, Ascaphus montanus, in Montana. Canadian Field Naturalist 115(2): 251-256.
    • Altig, R. 1969. Notes on the ontogeny of the osseous cranium of Ascaphus truei. Herpetelogica 25:59-62.
    • Altig, R., and E.E. Brodie. 1972. Laboratory behavior of Ascaphus truei tadpoles. Journal of Herpetology 6: 21-24.
    • Black, J.H. and J.N. Black. 1968. Frog with a tail. Montana Outdoors 3(3): 3 p.
    • Black, J.H. and R. Timken. 1976. Endangered and threatened amphibians and reptiles in Montana. p 36–37. In R.E. Ashton, Jr. (chair). Endangered and threatened amphibians and reptiles in the United States. Society for the Study of Amphibians and Reptiles Herpetological Circular 5: 1-65.
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    • Boundy, J. 2001. Herpetofaunal surveys in the Clark Fork Valley region, Montana. Herpetological Natural History 8: 15-26.
    • Brown, H.A. 1975b. Temperature and development of the tailed frog (Ascaphus truei). Comparative Biochemistry and Physiology 50A: 397-405.
    • Brown, H.A. 1989a. Developmental anatomy of the tailed frog (Ascaphus truei): a primitive frog with large eggs and slow development. Journal of Zoology London 217: 525-537.
    • Brown, H.A. 1990a. Morphological variation and age-class determination in overwintering tadpoles of the tailed frog, Ascaphus truei. Journal of Zoology 220: 171-184.
    • Brown, H.A. 1990b. Temperature, thyroxine, and induced metamorphosis in tadpoles of a primitive frog, Ascaphus truei. General and Comparative Endocrinology 79(1): 136-146.
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    • Bury, R.B. 1968. The distribution of Ascaphus truei in California. Herpetologica 24(1): 39-46.
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    • Bury, R.B., G.M. Fellers, and S.B. Ruth. 1969. First records of Plethodon dunni in California, and new distributional data on Ascaphus truei, Rhyacotriton olympicus, and Hydromantes shastae. Journal of Herpetology 3: 157-161.
    • Bury, R.B., P. Loafman, D. Rofkar, and K.I. Mike. 2001. Clutch sizes and nests of tailed frogs from the Olympic Peninsula, Washington. Northwest Science 75(4): 419-422.
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    • Claussen, D.L. 1971. A comparative study of the thermal and water relations of the tailed frog, Ascaphus truei and the Pacific treefrog, Hyla regilla. Ph.D. Dissertation. University of Montana, Missoula, MT. 103 p.
    • Claussen, D.L. 1973a. The thermal relations of the tailed frog (Ascaphus truei) and the Pacific treefrog (Hyla regilla). Comparative Biochemistry and Physiology 44a: 137-153.
    • Claussen, D.L. 1973b. The water relations of the tailed frog (Ascaphus truei) and the Pacific treefrog (Hyla regilla). Comparative Biochemistry and Physiology 44a: 155-171.
    • Cochran, D.C. 1961. Type specimens of reptiles and amphibians in the United States National Museum. U.S. National Museum Bulletin (220) xv + 291pp.
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    • Daugherty, C.H. 1976. Freeze-branding as a technique for marking anurans. Copeia 1976: 836-838.
    • Daugherty, C.H. 1979. Population ecology and genetics of Ascaphus truei: an examination of gene flow and natural selection. Ph.D. dissertation, University of Montana. Missoula, MT. 143 pp.
    • Daugherty, C.H. and A.L. Sheldon. 1982. Age specific movement patterns of the frog Ascaphus truei. Herpetologica 38(4):468-474.
    • Daugherty, C.H. and F.W. Allendorf. 1977a. Divergence of populations: preliminary evidence relating to the Ehrlich-Raven hypothesis from Ascaphus truei. Abstract. Annual Report Issue of the Genetics Society of America 86(2): S14.
    • Daugherty, C.H. and F.W. Allendorf. 1977b. The taxonomic value of genetic distance: data from two amphibians. Abstract. American Zoologist 17(4): 973.
    • Daugherty, C.H. and F.W. Allendorf. 1979. Temporal genetic stability in a population of the tailed frog, Ascaphus truei. Abstract. American Zoologist 19(3): 962.
    • Daugherty, C.H., L.N. Wishard, and L.B. Daugherty. 1978. Sexual dimorphism in an anuran response to severe thermal stress. Journal of Herpetology 12(3): 431-432.
    • De Vlaming, V.L., and R.B. Bury. 1970. Thermal selection in tadpoles of the tailed frog, Ascaphus truei. Journal of Herpetology 4: 179-189.
    • Diller, L.V. and R.L. Wallace. 1999. Distribution and habitat of Ascaphus truei in streams on managed, young growth forests in north coastal California. Journal of Herpetology 33(1): 71-79.
    • Donaldson, L.R. 1934. The occurrence of Ascaphus truei east of the Continental Divide. Copeia 1934(4): 184.
    • Dupuis, L.A. and D. Steventon. 1999. Riparian management and the tailed frog in northern coastal forests. Journal of Forest Ecology and Management 124(1): 35-43.
    • Dupuis, L.A. and F.L.Bunnell. 1999. Status and distribution of the tailed frog in British Columbia. A report for Forest Renewal British Columbia, Victoria, British Columbia.
    • Dupuis, L.A. and P. Friele. 2004. River continuum concept and management efforts--The case of the tailed frog. Abstract. Northwestern Naturalist 85:73.
    • Dupuis, L.A., F.L.Bunnell,and P.A. Friele. 2000. Determinants of the tailed frog's range in British Columbia, Canada. Northwest Science 74(2): 109-115.
    • Enk, M. 1999. Preliminary results of amphibian monitoring on the Lewis and Clark National Forest. Intermountain Journal of Sciences 5(1-4): 48.
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    • Feminella, J.W. and C.P. Hawkins. 1994. Tailed frog tadpoles differentially alter their feeding behavior in response to non-visual cues from four predators. Journal of the North American Benthological Society 13: 310-320.
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    • Franz, R. 1970. Egg development of the tailed frog under natural conditions. Bulletin of the Maryland Herpetological Society 6(2): 27-30.
    • Franz, R. 1970b. Food of larval tailed frogs. Bulletin of the Maryland Herpetological Society 6: 49-51.
    • Franz, R. 1971. Notes on the distribution and ecology of the herpetofauna of northwestern Montana. Bulletin of the Maryland Herpetological Society 7: 1-10.
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    • Hailman, J.P. 1982. Extremely low ambient light levels of Ascaphus truei. Journal of Herpetology 16: 83-84
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