Coastal Tailed Frog
(Ascaphus truei)
This primitive frog and its closest relative, the Rocky Mountain tailed frog, are distinctive among frogs and toads in having an intromittent organ, resembling a tail, for internal fertilization, an adaptation to ensure successful mating in the fast-flowing streams where the species live. Although listed as Least Concern on the IUCN Red List of Threatened Species, this species is sensitive to the effects of logging, which cause sedimentation and increase in water temperature. The genus Ascaphus has already survived two mass extinctions, but unless habitat loss and degradation is stopped the coastal tailed frog may join those which have already succumbed to the current, human induced, group of species losses, considered by many to be the sixth mass extinction event since life began.
Urgent Conservation Actions
Management of the remaining habitat with consideration of the needs of the species is required
Western Canada and the United States.
Evolutionary Distinctiveness
Order: Anura
Family: Leiopelmatidae
Leiopelmatidae is the most primitive of all the frog families, having diverged from all other amphibians approximately 245 million years ago in the early Triassic period, before the evolution of the dinosaurs. The family contains two genera, Ascaphus, the most primitive of all frogs, and Leiopelma. The Leiopelmatidae are unique among frogs in a number of ways, including the presence of vestigial tail-wagging muscles (which links this family to the more primitive salamanders) and in that, although they hop like other frogs with simultaneous leg movements, frogs in this family swim with alternate leg kicks.

The genus Ascaphus diverged from its closest relative, Leiopelma, over 200 million years ago, just before the Triassic-Jurassic boundary. In evolutionary terms bats and dolphins share more history than this genus and its closest relative, the Leiopelma, and this genus has survived two mass extinctions, the Triassic-Jurassic extinction event and the Cretaceous-Tertiary extinction event. This genus is unique among frogs and toads in possessing an intromittent organ developed for internal fertilization.

Two extinct genera of the family Leiopelmatidae are known from Patagonian Argentina, Vieraella from the early Jurassic and Notobatrachus from the late Jurassic. Notobatrachus were much larger than the extant Leiopelmatidae genera, growing to 15 cm in length.
The coastal tailed frog is relatively small and slender amphibian with a slightly flattened body and prominent large eyes. Its colouration ranges from olive or grey to almost black, with a pale underside. The upper side has numerous dark spots and there are often dark stripes on the limbs and well as a dark stripe running from the snout through the eye, and a pale yellowish to green triangle on its snout. This species has slender toes, although the outer toe on the hind feet is significantly thicker than the others, with little webbing. There is no external eardrum or vocal sac.

Members of the family Leiopelmatidae are the only frogs which have vestigial tail-wagging muscles, and the genus Ascaphus is unique as the males have a tail-like intromettent organ which gives the genus the name ‘tailed frogs’. The intromittent organ is in fact an extension of the cloaca, and functions as an organ for copulation which passes sperm directly into the body of the female during amplexus for internal fertilization.

The slate grey tadpoles of the coastal tailed frog have a white to pinkish tail bordered by a dark band, and grow to 3 cm before metamorphosis. Tadpoles have large sucking mouthparts which they need to hang on to rocks in the strong currents in the fast flowing streams in which they live
The coastal tailed frog is an aquatic and nocturnal species; adults, which remain under rocks during the day but emerge to feed on terrestrial and aquatic invertebrates at night, are extremely site-faithful and usually breed in their natal streams.

Breeding occurs from May to September when internal fertilization, an unusual breeding strategy among frogs, via the male intromittent organ takes place. This strategy allows the species to breed in the fast-flowing streams in which it lives. Copulation lasts from 24 to 30 hours. Egg deposition is delayed until the following summer when water flows are at their lowest, a further adaptation to rapid current in the frog’s stream habitat. At this time adults deposit strings of eggs to the downstream surface of rocks in mountain streams, where the tadpoles develop.

Newly hatched tadpoles are 10 to 15 mm long, but grow to approximately 30 mm before metamorphosis. The tadpoles feed on algae and invertebrates, and use their sucking mouthparts to grip on to rocks and any other solid surface available, even including human flesh; tadpoles prefer a rocky to a sandy of gravel substrate. It takes up to five years for metamorphosis to take place because the short warm season in this part of North America means growth is slow. It can take up to eight years for an adult coastal tailed frog to reach sexual maturity, and an individual may live for up to 14 years.
The coastal tailed frog inhabits clear, cold, fast-flowing mountain streams, and is more common in older temperate coniferous forests which more often contain the species’ preferred microclimate and microhabitat more often than recently cut stands. Individuals can be found on land in forests and more open areas when the weather is wet, but during drier weather this frog remains closer to the river on the moist banks.
Population Estimate
The population of the coastal tailed frog is probably larger than 10,000 individuals throughout the whole range, although the exact population size is unknown; the species is common in areas with suitable habitat
Population Trend
Little is known about the population trends of the coastal tailed frog, but it is thought that the population is likely to be declining as a result of degradation and loss of the species natural habitat.
The coastal tailed frog is listed as Least Concern on the 2007 IUCN Red List of Threatened species.
Tailed frogs are known to be sensitive to the effects of logging, including sedimentation and the resultant rise in water temperature, presumably caused by the canopy loss. One study found that tailed frogs were absent from clear cut sites. However, it is thought that current logging practices are not as harmful to the species as historic practices, and sensitivity to timber harvesting might be related to surface geology.
Conservation Underway
In some areas streams are protected from timber harvesting, for example there may be an equipment exclusion zones and tree retention zone from 15-30m on each side of the stream. Furthermore, this species is found within a number of National Parks and Wilderness Areas, which offer some protection.
Conservation Proposed
The maintenance of suitable habitat is essential, and the establishment of stream corridors would ensure that populations do not become fragmented as a result of habitat degradation. Management plans for protected areas should consider the needs of the species, and be designed with these in mind. Monitoring of populations is required to ensure that any declines are identified as early as possible.
AmphibiaWeb: Information on amphibian biology and conservation [web application]. 2006. Berkeley, California: AmphibiaWeb. Available: amphibiaweb. Accessed: 08 December 2006.

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

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. 33:71-79.

Duellmand, W. E. and Trueb, L. 1986. Biology of Amphibians. McGraw-Hill, Inc, USA.

Frost, Darrel R. 2006. Amphibian Species of the World: an Online Reference. Version 4 (17 August 2006). Electronic Database accessible at: . American Museum of Natural History, New York, USA.

Halliday, T. and Adler, C. (eds.). 2002. The new encyclopedia of reptiles and amphibians. Oxford University Press, Oxford.

IUCN, Conservation International and NatureServe. 2006. Global Amphibian Assessment. Global Amphibian Assessment. Accessed on 08 December 2006.

Nielson, M., Lohman, K. and Sullivan, J. 2001. Phylogeography of the tailed frog (Ascaphus truei): implications for the biogeography of the Pacific Northwest. Evolution. 55:147-160.

Obst, F.J., Richter, K. and Jacob, U. 1984. The Completely Illustrated Atlas of Reptiles and Amphibians for the Terrarium. T.F.H. Publication Inc., N.J., U.S.A.

Russell, A. P. and Bauer, A. M. 1993. The Amphibians and Reptiels of Alberta. University of Calgary Press and University of Alberta Press, Alberta, Canada.

Savage, J. M. 2002. The Amphibians and Reptiles of Costa Rica: A herpetofauna between two continents, between two seas. University of Chicago Press, Chicago and London.

Welsh, H.H., Jr. 1990. Relictual amphibians and old-growth forests. Conservation Biology. 4:309-319.

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