Species: Tailed Frog Ascaphus truei

Family: Ascaphidae Order: Anura Class: Amphibia

Species note author: Carlos Davidson
Reviewed by: Amy Lind and Hartwel Welsh
Date: September 1993

Management Status: California Species of Special Concern. This species was a federal Candidate 2 species before that category was abolished by the Fish and Wildlife Service.

The Tailed Frog (Ascaphus truei) is a small (2.5cm-5.1cm) primitive frog inhabiting cold, rocky streams in the Cascades and coastal ranges from British Columbia south to Northwestern California, and inland in the Rocky Mountians of southern British Columbia, Montana and Idaho, and the mountains of eastern Washington and Oregon (Stebbins 1985). (See Stebbins 1985 for a range map).

Ascaphus truei is the only species in the family Ascaphidae and is most closely related to three species of New Zealand frogs in the genus Leiopelma (Stebbins 1985). Tailed Frogs are unique in several respects. They are one of the longest lived anurans with a life span of 15 to 20 years, and have the longest larval period and the longest time to sexual maturity of any North American frog (Daugherty and Sheldon 1982a). Ascaphus are one of only a few frogs species with internal fertilization (another is the African toad Nectophrynoides occidentalis (Brown 1975)).

Range in CA

counties: Del Norte, Siskiyou, Humboldt, Mendocino, Trinity, Shasta, Tehema (Bury 1968).

Aquatic Habitat

Ascaphus habitat is often referred to as mountain streams, but Ascaphus is also found in steep walled valleys and coastal creeks (Bury 1968, Metter and Pauken 1969). In one location (Mill Creek, Humbolt county) a tadpole was collected in a coastal creek 40 feet from the Pacific high tide line. There is one recorded capture from a lake (Bury 1968).

All Ascaphus life stages have very narrow temperature requirements. Eggs require temperatures between 5^oC and 18.5^oC, the narrowest thermal tolerance and lowest maximum temperature of any North American frog (Brown 1975). For adults, Claussen (1973) estimated incipient lethal temperature as between 23.4^oC and 24.1^oC. Metter (1966) found exposure to 22^oC water killed adults, although tadpoles could survive higher temperatures. Observed temperatures in streams with Ascaphus generally range between 0^oC and 16^oC (Noble and Putnam, 1931, Metter 1964, Bury 1968, deVlaming and Bury 1970, Clausen 1973, Nussbaum et al. 1986), with a single report of tadpoles in water as warm as 19.5^oC (Hawkins et al. 1988). Welsh (1990) found a statistically significant correlation between water temperature and abundance of Ascaphus. Hawkins et al. (1988), on the other hand, did not find a statistically significant correlation between abundance and water temperature. The authors speculated that the lack of correlation may have been due to shaded areas upstream that were sources for tadpoles that then traveled downstream to warmer water (Hawkins et al. 1988).

Hawkins et al. (1988) found higher relative abundances of tadpoles in sites with average substrate size between 10 and 30 cm. However at night 42 percent of tadpoles were found in areas with greater than 30 cm substrates. Altig and Brodie (1972) found tadpoles in the labratory avoided substrates with sand (<5mm diameter) and pebbles (18-36mm diameter) and prefered substrates with gravel (55-96mm diameter) and rocks (85-125mm diameter). Stebbins (1985) describes Ascaphus habitat as rocky streams. There is no quantitative data on adults.

Metter (1964) describes several sites where there is little change in water temperature at the edge of the range of a local Ascaphus population, suggesting that in some cases water temperature may not be a limiting factor.

Terrestrial habitat

Ascaphus is not associated with any particular plant species (Metter 1964). Stebbins (1985) describes Ascaphus habitat as humid forest of Douglas fir, spruce, redwood, maple, alder and bay, but adds trees may be absent and grassland, chapparral or shrubs may be interspersed. Metter (1964) describes the vegetation at number of sites with Ascaphus as mixed conifer-hardwood and mixed pine and fir. None of the sites were in California. Noble and Putnam (1931) report Ascaphus from above timberline in the Olympic Mountains, Washington. Gaige (1920) reports Ascaphus in an alpine meadow (Mt. Steel, Jefferson county Washington).

In California Ascaphus populations have been found in a variety of habitats including Sitka spruce, redwood, Douglas fir, Klamath mixed conifer and ponderosa pine forests as well as single populations in Yellow pine forest and Northern Coastal Shrub (Bury 1968).

Feeding

Adults eat primarily arthropods, but also a variety of other prey, eating whatever comes their way including snails, ticks, mites, colembolans, dipterans, moths, ants, mayflies, crickets, and lacewings (Metter 1964). Captive adults prefered spiders over a number of other food items (Held 1985). Adults are apparently inefficient underwater feeders, as most prey species are terrestrial (Metter 1964). Metter (1964) examined tadpole guts and found tadpoles feed primarily on diatoms which are scraped from submerged rocks. Small amounts of filamentous algae and desmids were also eaten. In June tadpoles consumed large amounts of pollen. Altig and Brodie (1972) tested and rejected the idea that tadpoles eat suspended plankton.

Reproduction

Adults are not reproductively mature until at least their seventh year, roughly twice the age of first reproduction of any other frog (Daugherty and Sheledon 1982a). Mating occurs in the early fall (Late August and September in Oregon, Nussbaum et al. 1986), (late September and early October in Northwestern Washington, Brown 1975). The "tail" of the male, actually a unique copulatory organ, is inserted in the female as the male clasps the female around the pelvis. Mating takes place in the water (Noble and Putnam 1931). Tail frogs are voiceless (Noble and Putnam 1931, Nussbaum et al. 1986). Females store sperm until the following July when eggs are laid in strings attached to the underside of rocks in the stream bottom (Gaige 1920, Nussbaum et al. 1986). Females lay eggs every other year, execpt in coastal areas where they may lay every year (Metter 1964, Nussbaum et al. 1986). Metter (1964) reported an average of 37 eggs per female in a coastal population and an average of 68 eggs per female in an inland population. Eggs require from a month (Noble and Putnam 1931) to six weeks (Brown 1990) to hatch. Hatching takes place from late August to early September (Brown 1990). Hatchlings overwinter at the nest site (under a large rock), not venturing out until the first spring following hatching (Metter 1964). Tadpole mortality is largely due to aperiodic floods, which adults can escape by leaving the stream (Metter 1968, Daugherty and Sheldon 1982a).

There is disagreement on the length of the larval period. (Metter 1964, 1967) Daugherty and Sheldon (1982a) and Nussbaum et al. 1986 reported that tadpoles transform after two years in the coastal ranges and three years in the interior (Montana, Idaho). More recently Brown (1990) reported a larval period of four years. Whether after two, three or four years, tadpoles complete metamorphosis in late summer (Brown 1990).

Activity

Tail frogs are primarily noctural, spending the day hidden under rocks in the stream bottom (Metter 1964, 1967). In coastal areas in wet weather Ascaphus adults leave the vicinity of the stream to forage on land up to 100 yards from water (Noble and Putnam 1931, Metter 1967). In most inland areas (Idaho and Montana, Eastern Oregon and Washington) adults in most cases do not leave the stream (Metter 1967). In dry weather adults, emerge at dusk or later, and confine foraging to the stream banks (Metter 1967). Adults appear to be active out of the water only at times of high humidity (Nussbaum et al. 1986). Tailed Frogs have one of the lowest dessication tolerances among anurans (Clausen 1973b).

Tadpoles are most often observed clinging to rocks in fast moving water although they are sometimes seen swiming in slow pools (Gaige 1920, Metter 1964). At night tadpoles move out of the water to the top of rocks (Noble and Putnam 1931, Altig and Brodie 1972).

In the Coastal ranges Ascaphus is active year round. In the Rocky Mountains Ascaphus is active only from May to September, spending the winter under rocks in the stream bottom (Daugherty and Sheldon 1982a).

Movement/Migration

Tailed frogs have extremely high site fidelity, moving little throughout the year and from season to season (Daugherty and Sheldon 1982b). In a study in Montana, Daugherty and Sheledon (1982b) found the majority of adults females remained in the same 20 meter stream segment over a number of years. Daugherty and Sheldon (1982b) speculate that Ascaphus may move more in the Coastal ranges due to greater terrestrial moisture and year-round activity patterns. Brown (1975) reported aggregations of adult females during egg laying season (July), but this has not been confirmed by other authors.

Predators/Niche

In some small streams Ascaphus tadpoles constitute 90 percent of herbivore biomass (Hawkins et al. 1988). Predators include garter snakes (Thamnophis spp.), Cutthroat trout (Salmo clarki) and American dippers (Cinclus mexicanus) (Daugherty and Sheldon 1982a). Larval Pacific Giant Salamander (Dicamptodon ensatus) and Red Legged Frog (Rana aurora) eat tadpoles (Bury 1968). Ascaphus populations seem to coexist with fish (Metter 1964).

Management Concerns

A number of authors have reported that Ascaphus populations have disappeared from a site following logging (Gaige 1920, Noble and Putnam 1931, Metter 1964, Nussbaum et al. 1986). Nussbaum et al. (1986) speculate that clearcutting affects Ascaphus by raising water temperatures and increasing siltation. Bury (1968) reports Ascaphus populations in previously logged sites along the California coast (no time was given since logging) and suggests that the effects of logging may be less in areas with a maritime climate. However, Corn and Bury (1989) studied 43 sites in the Coastal mountains of Oregon, and found Tailed frogs present in 96 percent of forested sites but only 35 percent of logged sites.

Good habitat for Ascaphus is likely to be highly insular (Daugherty and Sheldon 1982b). Fast flowing streams are broken into segments by lakes, marshes and slow sandy areas that are avoided by Ascaphus. Suitable streams are separated from each other by dry ridges. There is probably little migration between sub-populations (Daugherty and Sheldon 1982b). Metter (1967) and Metter and Pauken (1969) examined morphological variation among Ascaphus populations and concluded that there appears to be little gene flow between sub-populations. Site fidelity combined with low reproductive rates means recolonization of good habitat following local extinctions is likely to be slow (Hawkins et al. 1988).

Literature Cited

Altig, R. and E. D. Jr. Brodie. 1972. Laboratory behavior of ascaphus truei tadpoles. Journal of Herpetology 6 (1): 21­24.

Brown, H. A. 1990. Morphological variation and age­class determination in overwintering tadpoles of the tailed frog ascaphus truei. J. Zool. Lond. 220: l7l­l84.

­­­. 1975. Temperature and development of the tailed frog, ascaphus truei. In Comp. Biochem. Physiol. 397­405. Great Britain: Pergamon Press.

Bury, R. B. 1968. The distribution of ascaphus truei in California. Herpetologica 24 (l): 39­46.

Claussen, D. L. 1973. The thermal relations of the tailed frog, ascaphus truei, and the Pacific treefrog, hyla regilla. In Comp. Biochem. Physiol. 137­153. Great Britain: Pergamon Press.

­­­. 1973. The water relations of the tailed frog, ascaphus truei and the Pacific treefrog, hyla regilla. In Comp. Biochem. Physiol. 155­171. Great Britain: Pergamon Press.

Corn, P. S. and R. B. Bury. 1989. Logging in western Oregon: responses of headwater habitats and stream amphibians. Forest Ecology and Management 29: 39­57.

Daugherty, C. H. and A. L. Shelton. 1982a. Age­determination, growth, and life history of a Montana population of the tailed frog (ascaphus truei). Herpetologica 38 (4): 46l­468.

Daugherty, C. H. and A. L. Sheldon. 1982b. Age­specific movement patterns of the frog ascaphus truei. Herpetologica 38 (4): 468­ 474.

deVlaming, V. L. and Bury R. Bruce. 1970. Thermal selection in tadpoles of the tailed frog, ascaphus truei. Journal of Herpetology 4 (3­4): 179­189.

Gaige, H. T. 1920. Observations upon the habits of ascaphus truei stejneger. Occasional papers of the museum of zoology. 84. University of Michigan, Ann Arbor, Michigan.

Hawkins, C. P., L. J. Gottschalk and S. S. Brown. 1988. Densities and habitat of tailed frog tadpoles in small streams near Mt. St. Helens following the 1980 eruption. J. N. Am. Benthol. Soc. 7 (3): 246­252.

Held, S. P. 1985. Maintenance, exhibition, and breeding of the tailed frog, ascaphus truei, in a zoological park. Herp Review 16 (2): 48­51.

Metter, D. E. 1968. The influence of floods on population structure of Ascaphus truei Stejneger. Journal of Herpetology l: 105­106.

­­­. 1967. Variation in the ribbed frog Ascaphus truei Stejneger. Copeia 3: 634­649.

­­­. 1966. Some temperature and salinity tolerances of Ascaphus truei Stejneger. J. Idaho Acad. Sci. 4, 44-47

­­­. 1964. A morphological and ecological comparison of two populations of the tailed frog, Ascaphus truei Stejneger. Copeia l: l8l­204.

Metter, D. E. and R. J. Pauken. 1969. An analysis of the reduction of gene flow in ascaphus truei in the Northwest U. S. since the Pleistocene. Copeia 2: 301­307.

Noble, G. K. and P. G. Putnam. 1931. Observations on the life history of ascaphus truei stejneger. Copeia 3: 97­101.

Nussbaum, R. A., E. D. Brodie and R. M. Storm. 1983. Reptiles and amphibians of the Pacific Northwest. Moscow Idaho: University Press of Idaho.

Stebbins, R. C. 1985. A field guide to western reptiles and amphibians. Houghton Mifflin. Boston, Mass.

Welsh, H. H. 1990. Relictual amphibians and old­growth forests. Conservation Biology 4 (3): 309­3l9.