Ascaphus trueiCoastal Tailed Frog(Also: Tailed Frog)

Geographic Range

Tailed frogs occur from northwestern California north to the Portland Canal and Nass River of British Columbia. This range is bordered by the Cascade Mountains to the east and the Pacific coast to the west. Several separate populations are also found in the Blue Mountains of southeastern Washington and northeastern Oregon as well as in the northern Rocky Mountains of northern Idaho and western Montana. (Stebbins, 2003; Adams and Pearl, 2005; Leonard, et al., 1993; Mallory, 2004; Stebbins, 2003)


Tailed frogs clear, cold streams of mountainous regions with step-pools, such that the slope is neither too shallow nor too steep. They inhabit a wide range of elevations from coastal to mountainous. Stream temperatures must remain cool even in summer months, as this species is known to have narrow temperature tolerances. Also, coarse substrates are favored for egg-laying and over-wintering events. As larvae do exhibit a long developmental period, stream habitats must be permanent features of the landscape. Juveniles and adults, however, further require the presence of a mature or old growth forest alongside their stream habitat. While they will not venture too far from the water, juveniles and adults will utilize riparian vegetation for food and refuge. This vegetation is also important to larvae, as it helps to control stream temperatures and prevent excessive sedimentation through bank stabilization. (Adams and Pearl, 2005; Mallory, 2004; Metter, 1964; Wallace and Diller, 1998)

  • Aquatic Biomes
  • rivers and streams
  • Range elevation
    0 to 2557 m
    0.00 to 8389.11 ft

Physical Description

Since tailed frogs spend their life in association with fast-flowing streams, they have evolved some morphological adaptations that stand out from other frogs and toads. For example, the lungs are greatly reduced, presumably to control buoyancy, and the toe tips are hard and keratinized, to facilitate crawling among rocks on the stream bottom. (Adams and Pearl, 2005; Leonard, et al., 1993; Metter, 1964; Stebbins, 2003)

Juveniles and adults are small, typically ranging from 2.2 to 5.1 cm in snout-vent length. Overall, color is usually comparable to the tailed frog’s substrate and may vary from tan to chocolate brown or olive green. Regardless of the color, its skin has a characteristic rough feel. Moreover, the head is comparatively large and flattened with a light triangular-shaped mark generally present between the snout and eyes. The eyes themselves have visibly vertical pupils, and a dark stripe extends from the snout to the shoulder. Some more obvious adaptations to its streamside habitat include a slight webbing of the toes, with the outer hind toes also flattened. In addition, they lack tympani or ear membranes and, as a result, lacks the capacity to communicate acoustically, a likely adaptation to the steady sound of flowing water. Tailed frogs get their common name from another aquatic adaptation: males have a short, tail-like copulatory organ used during internal fertilization. Tailed frogs exhibit additional sexual dimorphism in that males are smaller than females, and they develop black, horny pads on the insides of their thighs during the mating season to aid gripping females during amplexus. (Adams and Pearl, 2005; Leonard, et al., 1993; Metter, 1964; Stebbins, 2003)

Tadpoles average little more than 11 mm after hatching, but may grow to 65 mm in length before metamorphosis. Initially, hatchlings have no color, but are instead identified according to the presence of a prominent yolk sac seen in the abdomen. However, tadpoles eventually take on a black to brownish-grey coloration of the body that is covered with black speckling. A white dot discernible on the tip of the tail and an obvious copper-colored bar between the eyes and snout are additional field marks for identification. Tailed frog tadpoles also have some adaptations to keep from being swept away by stream currents. The body is flattened ventrally and the tail is laterally compressed. Moreover, the mouth has evolved into an oral disc that is sucker-like, allowing for attachment to rocks. Eggs are unpigmented and are laid in a gelatinous string beneath a rock in shallow water. (Adams and Pearl, 2005; Leonard, et al., 1993; Metter, 1964; Stebbins, 2003)

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • sexes shaped differently
  • Range length
    2.2 to 5.1 cm
    0.87 to 2.01 in


While most frogs and toads exhibit external fertilization, tailed frogs unique in that they have internal fertilization. Female tailed frogs purposefully attach their eggs to the bottom of big rocks or boulders found submerged in the stream. Hatching occurs about six weeks after deposition of the eggs. Tadpoles utilize their large yolk sac for nourishment throughout the winter months, after which development of a suctorial mouth allows them to prey upon other organisms. Following one to four years, metamorphosis takes place, producing juvenile tailed frogs that differ dramatically in appearance from their previous larval form. Metamorphosis can last up to 60 days. The age that juveniles reach sexual maturity varies geographically, with coastal populations maturing at 2 to 3 years old and montane populations maturing at 8 to 9 years old. (Adams and Pearl, 2005; Leonard, et al., 1993; Mallory, 2004; Stephenson and Verrell, 2003; Wallace and Diller, 1998)


Tailed frogs are unique among the anurans in exhibiting a combination of amplexus and copulation during courtship and mating. Courtship occurs at the onset of fall, between September and October, and is carried out in the water. During courtship, a male typically lunges or swims suddenly toward a female of the same species. Clasping the female’s body directly anterior to her pelvic region, the male may then perform either inguinal or ventral amplexus. Once in the proper position, copulation can follow, the male's erect “tail” inserted into the female’s cloaca. To press closer to the female during copulation, the male may repeatedly produce thrusts of his pelvic region, his “tail” still within the cloaca. (Adams and Pearl, 2005; Leonard, et al., 1993; Mallory, 2004; Stephenson and Verrell, 2003; Wallace and Diller, 1998)

Tailed frog females have been shown to reproduce biennially, while males may mate annually. This behavior may vary geographically. Although courtship and mating occur in the fall, tailed frog females store the sperm and do not deposit eggs until June or July. When deposition finally takes places, a dual strand of 44 to 85 small-sized eggs is fixed to the base of a rock or boulder within the stream system. After approximately six weeks, hatchlings then appear. The tadpole or larval stage may last anywhere from one to four years, geographic location likely impacts the length. Coastal populations spend 1 to 3 years in the larval state, whereas montane or inland populations spend 3 to 4 years. Tailed frog tadpoles undergo metamorphosis, which includes absorbing their tails, developing an adult mouth, losing the suction mouth, and developing legs. A juvenile may not reach reproductive maturity until it is 2 to 8 years old, varying geographically. (Adams and Pearl, 2005; Leonard, et al., 1993; Mallory, 2004; Stephenson and Verrell, 2003; Wallace and Diller, 1998)

  • Breeding interval
    Tailed frog females breed biennially, while males may breed annually.
  • Breeding season
    Tailed frogs breed from September through October (fertilization) and females lay eggs from June to July (oviposition).
  • Range number of offspring
    44 to 85
  • Average time to hatching
    6 weeks
  • Range age at sexual or reproductive maturity (female)
    2.5 to 4 years
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Range age at sexual or reproductive maturity (male)
    1.5 to 4 years
  • Average age at sexual or reproductive maturity (male)
    3 years

There is little available information on parental care in tailed frogs.


With a maximum lifespan of at least fourteen years, and from 2 to 9 years required to attain sexual maturity, tailed frogs have one of the longer life histories known among anurans. (Adams and Pearl, 2005; Daugherty and Sheldon, 1982)

  • Range lifespan
    Status: captivity
    14 (high) years


Juvenile and adult tailed frogs are often active nocturnally, foraging for food under the cover of night. Although they typically stay close to the streamside, juveniles and adults may move a modest distance into the neighboring mature or old growth forests. Tadpoles, on the other hand, may display either nocturnal or diurnal behavior, the choice of when to forage for food likely dependent on the presence or absence of certain predatory species. Moreover, tadpoles differ in that they are largely sedentary within the stream system. Activity dramatically decreases during winter, though they do not hibernate, and some individuals remain active. (Adams and Pearl, 2005; Leonard, et al., 1993; Mallory, 2004; Metter, 1964)

Home Range

Territory size is unknown for tailed frogs.

Communication and Perception

Communication through calls, as characteristic of most anurans, does not appear possible due to the absence of the tongue, vocal sacs, middle and external ear bones, and external eardrums which are critical to creating and perceiving sound. With acoustic communication lacking in tailed frogs, they are presumably reliant on visual and tactile cues to carry out courtship and mating activities. Still, more research is needed in this subject of study, as chemical cues may prove important to communication as well. (Adams and Pearl, 2005; Hallock and McAllister, 2005; Leonard, et al., 1993; Stephenson and Verrell, 2003; Vitt and Caldwell, 2009)

Food Habits

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • zooplankton
  • Plant Foods
  • algae


Little is known regarding potential predators of tailed frogs, as observations regarding this subject of study are few in number. Of those accounts that exist, common garter snakes, shrews (Sorex) and western terrestrial garter snakes were observed consuming post-metamorphic tailed frogs. There are also accounts of hellgrammites (Megaloptera), larval Cope’s giant salamanders and Pacific giant salamanders consuming larval tailed frogs. Other predators include trout (Salmonidae), sculpins and dippers. (Adams and Pearl, 2005; Leonard, et al., 1993; Lund, et al., 2008)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Tailed frog tadpoles can actually act as the dominant herbivore in some stream habitats. However, tailed frogs are restricted to aquatic lotic systems as a tadpole. As a juvenile or adult on the other hand, they may play an active part in both its aquatic and adjacent terrestrial ecosystem through interaction with its prey and predators. (Mallory, 2004)

Economic Importance for Humans: Positive

Due to the sensitivity of tailed frogs to alterations of their habitat, this stream-dwelling species may serve as an indicator species in assessing ecosystem health. (Adams, 1993)

Economic Importance for Humans: Negative

There are no known negative impacts of tailed frogs on humans.

Conservation Status

Ascaphus truei is ranked as a species of “Least Concern” on the IUCN Red List but are a “Species of Concern” for the Pacific region on the United States Fish and Wildlife Endangered Species List. The reason behind its status on either list is the fact that tailed frogs may be impacted by logging and construction activities. These practices can negatively alter tailed frogs' habitats by causing stream temperatures to rise and siltation to occur. (Adams and Pearl, 2005; Hammerson and Adams, 2010; "Tailed frog (Ascaphus truei)", 2010)


Ashley Potter (author), Michigan State University, James Harding (editor), Michigan State University, Rachelle Sterling (editor), Special Projects, Catherine Kent (editor), Special Projects.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


mainly lives in water that is not salty.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


having more than one female as a mate at one time


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).


specialized for leaping or bounding locomotion; jumps or hops.

seasonal breeding

breeding is confined to a particular season


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


uses sight to communicate


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


U.S. Fish and Wildlife Service. 2010. "Tailed frog (Ascaphus truei)" (On-line). Species Profile. Accessed November 26, 2010 at

Adams, M., C. Pearl. 2005. Amphibian Declines: The Conservation Status of United States Species. Ascaphus truei. Berkley, CA: University of California Press.

Adams, M. 1993. Summer Nests of the Tailed Frog (Ascaphus truei) from the Oregon Coast Range. Northwestern Naturalist, 74/1: 15-18. Accessed November 26, 2010 at

Daugherty, C., A. Sheldon. 1982. Age-Determination, Growth, and Life History of a Montana Population of the Tailed Frog (Ascaphus truei). Herpetologica, 38/4: 461-468.

Hallock, L., K. McAllister. 2005. "Coastal Tailed Frog" (On-line). Accessed November 26, 2010 at

Hammerson, G., M. Adams. 2010. "Ascaphus truei" (On-line). The IUCN Red List of Threatened Species. Accessed November 26, 2010 at

Leonard, W., H. Brown, L. Jones, K. McAllister, R. Storm. 1993. Amphibians of Washington and Oregon. Seattle, WA: Seattle Audubon Society.

Lund, E., M. Hayes, T. Curry, J. Marsten, K. Young. 2008. Predation on the Coastal Tailed Frog (Ascaphus truei) by a Shrew (Sorex spp.) in Washington State. Northwestern Naturalist, 89: 200-202. Accessed November 26, 2010 at

Mallory, A. 2004. Coastal Tailed Frog: Ascaphus truei. Accounts and Measures for Managing Identified Wildlife: Southern Interior Forest Region, 2004: 77-86. Accessed November 26, 2010 at

Metter, D. 1964. A Morphological and Ecological Comparison of Two Populations of the Tailed Frog, Ascaphustruei Stejneger. Copeia, 1964/1: 181-195. Accessed November 26, 2010 at

Stebbins, R. 2003. A Field Guide to Western Reptiles and Amphibians. New York, NY: Houghton Mifflin.

Stephenson, B., P. Verrell. 2003. Courtship and mating of the tailed frog (Ascaphus truei). Journal of Zoology, 259/1: 15-22. Accessed November 26, 2010 at

Vitt, L., J. Caldwell. 2009. Herpetology, 3rd Edition. Burlington, MA: Academic Press.

Wallace, R., L. Diller. 1998. Length of the Larval Cycle of Ascaphus truei in Coastal Streams of the Redwood Region,Northern California. Journal of Herpetology, 32/3: 404-409. Accessed November 26, 2010 at