E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Ascaphus montanus Mittleman and Myers, 1949
Rocky Mountain Tailed Frog
Family: Ascaphidae

Species account author: Brent Matsuda.

Photo of species

© Larry Halverson  Email the photographer   (Photo ID #1190)

E-Fauna BC Static Map
Distribution of Ascaphus montanus in British Columbia
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Species Information

Much of the information for the Coastal Tailed Frog regarding morphology and habitat also applies to this species. The Rocky Mountain Tailed Frog and the Coastal Tailed Frog (Ascaphus truei) were formerly considered as single species (A. truei), but are now recognized as two species based on genetic and ecological differences (Nielson et al. 2001).

Tailed frogs are small (40-50 mm snout-vent length). They are the only members of family Ascaphidae and are considered to be "primitive" frogs, because they have nine presacral vertebrae, whereas most other frogs have 8, and they possess ribs, which have been lost in other groups of frogs. Adult males possess a short, cone-shaped "tail," which functions as a copulatory organ during mating. They are the only North American species that uses internal fertilization. Both tadpoles and adults possess morphological features functionally related to life in fast-flowing streams. Tadpoles have a flattened oral disc that produces a sucker-like mouth, which they use to attach to rocks in fast flowing water. The body is dorso-ventrally flattened, and the tail fin is low. Adults lack a tympanum (eardrum) and males do not call, which may be an adaptation to living within the constant noise of mountain streams. It is not known how mates find each other. While adults are mainly active at night, they can sometimes be found out and about in daytime, particularly in damp, cool settings.

Coastal species lay eggs later than the inland species, have smaller clutch sizes, shorter incubation periods and smaller hatching sizes than the Rocky Mountain Tailed Frog (Ascaphus montanus (Karraker et al., 2006).

Tailed frogs are the longest-living frogs in North America, estimated to live 15 years or more. Development to adulthood is lengthy; tadpoles can take one to four years to metamorphose depending on geographical location (Bury and Adams 1999) and 7-8 years to reach sexual maturity.



According to Matsuda et al. (2006), adult Tailed Frogs breed in the fall, with females laying 40 to 75 clear eggs in midsummer in small clusters attached to the undersides of rocks.. Tadpoles metamorphose at one to three years of age, usually in early spring. Transformed frogs reach sexual maturity in five to seven years and are estimated to live between 15 and twenty years (Matsuda et al. 2006).

The larvae of this species eat mostly diatoms, while adult frogs are generalists and feed on insects and other invertebrates.


Rocky Mountain Tailed Frogs live in permanent cold, fast moving stream habitats similar to that of the Coastal Tailed Frog. Although they may be found in fish-bearing streams, tailed frogs typically occur in non-fish bearing streams that flow over rocky substrates. Headwater streams are important for the species, which is vulnerable to logging and receive relatively little protection compared to salmon-bearing streams at lower elevations. Streams with step-pools and cobbled stretches, with low amounts of detritus and fine sediment flowing through old growth, or older-stage second growth forests with dense understory, are prime habitats (Dupuis and Steventon 1999; Wahbe and Bunnell 2003), although tadpoles can also be quite abundant in streams flowing through clearcuts. Tadpole densities in such streams however, should not be interpreted as an indicator of a healthy ecosystem as tadpole densities may be a short-term response to an abundance of food (i.e., algal growth) due to open exposure to sunlight resulting from lack of overhead canopy (Richardson and Neill 1998). If suitable habitat does not exist post-metamorphosis, then the population will not be sustainable (Matsuda 2001). Ultimately, the abundance of reproductive adults is a more reliable indicator of habitat quality and population sustainability (Van Horne 1983).


In British Columbia, two geographically limited, isolated populations are known from the extreme southeast of the province, separated from each other by the Rocky Mountain Trench. These populations are continuous with populations across the border in northern Idaho and northwestern Montana.


Conservation Concerns

Any activity that alters fast-flowing streams can be harmful to Tailed Frog habitat. Populations can be impacted by flushing of rocks and other debris down hillsides. Increased siltation and sedimentation from logging, development, or other activities affecting streams can fill refuges between rocks used for foraging, predator avoidance, temperature regulation, or protection from high water flows.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
NativeS2S3BlueT (Nov 2013)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

Species References

Adams, S. B., 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: 251-256.

British Columbia Ministry of Water, Land and Air Protection. 2004. Rocky Mountain Tailed Frog IN: Accounts and measures for managing identified wildlife. British Columbia Ministry of Water, Land and Air Protection, Victoria, BC. 52 pp.

Bury, R.B., and M.J. Adams. 1999. Variation in age at metamorphosis across a latitudinal gradient for the tailed frog, Ascaphus truei. Herpetologica 55: 283-91.

Daugherty, C.H. and A.L. Sheldon. 1982. Age-determination, growth, and life history of a Montana population of the tailed frog (Ascaphus truei) Herpetologica 38:461-468.

Daugherty, C.H. and A.L. Sheldon. 1982. Age-specific movement patterns of the frog Ascaphus truei. Herpetologica 38: 468-474.

Dupuis, L.A., F.L. Bunnell, and P.A. Friele. 2000. Determinants of the tailed frog’s range in British Columbia. Northwest Science 74 (2):109–115.

Karraker, N.E., D.S. Pilliod, M.J. Adams, E.L. Bull, P.S. Corn, L.V. Diller, L.A. Dupuis, M.P. Hayes, B.R. Hossack, G.R. Hodgson, E.J. Hyde, K. Lohman, B.R. Norman, L.M. Ollivier, C.A. Pearl and C.R. Peterson. 2006. Taxonomic and geographic variation in the oviposition of tailed frogs (Ascaphus spp.) Northwestern Naturalist 87(2): 87-97.

Matsuda, Brent M., David M. Green and Patrick M. Gregory. Amphibians and reptiles of British Columbia. Royal British Columbia Museum, Victoria.

Nielson, M., K. Lohman and J. Sullivan. 2001. Phylogeography of the Tailed Frog (Ascaphus truei): implications for the biogeography of the Pacific Northwest. Evolution 55: 147-60.

General References

Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2024-04-12 1:10:33 PM]
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