Tailed frogs are small (40-50 mm snout-vent length) with a large head. 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.
The Coastal Tailed Frog and Rocky Mountain Tailed Frog (Ascaphus montanus) 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).
According to Matsuda et al. (2006), adult Tailed Frogs breed in the fall, with females laying 35 to 100 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 three to five 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.
Although they may be found in fish-bearing streams, tailed frogs typically occur in non-fish bearing, permanent, cold, fast flowing mountain 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).
The Coastal Tailed Frog occurs in the Coast and Cascade Mountain Ranges, from northern California to the Alaskan panhandle. In BC, it is found in the Coast Mountains from the Lower Mainland to the Nass River on the North Coast,
within the windward and leeward drainages.
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.
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.
Dupuis L.A., and D. Steventon. 1999. Riparian management and the tailed frog in northern coastal forests. Forest Ecology and Management 124: 35-43.
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, B.M. 2001. The effects of clear-cut timber harvest on the movement patterns of Tailed Frogs (Ascaphus truei) in southwestern British Columbia. M.Sc. thesis, Department of Forest Sciences, University of British Columbia.
Matsuda, Brent M., David M. Green and Patrick M. Gregory. 2006. 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.
Richardson, J.S., and W.E. Neill. 1998. Headwater amphibians and forestry in British Columbia: Pacific giant salamanders and tailed frogs. Northwest Science 72: 122-123.
Van Horne, B. 1983. Density as a misleading indicator of habitat quality. Journal of Wildlife Management 47: 893-901.
Wahbe, T.R., and F.L. Bunnell. 2003. Relations among larval tailed frogs (Ascaphus truei), forest harvesting, stream microhabitat, and site parameters in southwestern British Columbia. Canadian Journal of Forest Research 33: 1256-1266.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. 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:
2020-09-21 7:28:06 PM]
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