Rocky Mountain Tailed Frog - Ascaphus montanus
(see State Rank Reason below)
State Rank Reason (see State Rank above)
Species is apparently secure and not at risk of extirpation or facing significant threats in all or most of its range.
- Details on Status Ranking and Review
ScoreF - 20,000-200,000 km squared (about 8,000-80,000 square miles)
Comment70,521 square Kilometers from Natural Heritage Program range maps
ScoreE - Relatively Stable (±25% change)
CommentAlthough forest management practices and fire regimes have changed over the last century it is unlikely that the amount of habitat for this species has changed more than 25%. Loss of old growth timber may have contributed to a reduction in suitable habitat, but the extent of the impact on this species is unknown.
ScoreU - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.
CommentTo date surveys have not been conducted with enough frequency to determine trend
ScoreG - Slightly threatened. Threats, while recognizable, are of low severity, or affecting only a small portion of the population or area.
CommentDegradation of stream habitat through logging or wildfire
SeverityLow - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.
CommentGiven current forest management practices, impacts should not persist for more than 50 years
ScopeLow - 5-20% of total population or area affected
CommentSpecies is found across a large area so impact to large portions of the population would be unlikely
ImmediacyLow - Threat is likely to be operational within 5-20 years.
CommentPossible within the next 20 years, but is not imminent.
ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).
CommentThis species has high fecundity, a moderate age of maturity, and recruitment can be low.
ScoreB - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.
CommentSpecies is associated with montane streams within forested areas across western Montana.
Raw Conservation Status Score
3.5 + 0 (geographic distribution) + 0 (environmental specificity) + 0 (long-term trend) + 0.75 (threats) = 4.25
Laid in a jelly string as a globular mass containing 28 to 86 eggs (Noble and Putnam 1931; Franz
1970a). Each ovum is creamy white and surrounded by two jelly layers which themselves lie
within the outer jelly string (Franz 1970a). Ovum diameters are approximately 4-5 mm, but total egg diameters, including the three jelly layers, are approximately 6-7 mm (Metter 1967, Adams 1993). Clutches from multiple animals may be laid together in the same nest site (Adams 1993).
Base color is variable from solid black, to gray, to solid brown. White flecks may be present and
most larvae have a white tail spot (Metter 1967). A large sucking disk is present around the
mouth. The spiracle is mid-ventral and opens under a flap (Metter 1968). Total length (TL) of
10-64 mm (up to 2 inches long) (Metter 1967, Franz 1971).
JUVENILES AND ADULTS
Pupil of the eye is vertical. This species lacks external ear drums (tympanums). The cloaca of males opens into a tear-shaped copulatory organ (the “tail”). Skin is a granulated texture. Base color is brown, reddish brown, or olive gray with yellow and gray mottling dorsally and a dark eye stripe. Ventrally cream to pinkish. The outer toe of the hind foot is broader than the other toes. Snout-vent length (SVL) of 20-57 mm (1.5-2 inches) (Daugherty 1979, Daugherty and Sheldon 1982a).
No other adult anuran species lack external ear drums (tympanums). No other larval anuran species have a large sucking disk around the mouth or are found in small swift streams.
Western Hemisphere Range
Until recently tailed frogs were recognized as a single species with a disjunct distribution. The coastal population, ranging from northwestern California to southwestern British Columbia separated by hundreds of miles from a Rocky Mountain population that includes isolated populations in the Blue, Wallowa and Seven Devils Mountains and a more continuous population that ranges from central Idaho to the southeast corner of British Columbia (Metter 1968a). However, allozyme and mitochondrial DNA analyses indicate that the Rocky Mountain and coastal populations differ to the extent that a separate species designation is warranted (Daugherty 1979, Nielson and Lohman 2000, Maxell et al. 2009). Populations in the Rocky Mountains and those in the Blue, Wallowa and Seven Devils Mountain Ranges are now recognized as the Rocky Mountain Tailed Frog (Ascaphus montanus) and coastal populations are now recognized as the Coastal Tailed Frog (Ascaphus truei) (Mittleman and Myers 1949, Maxell et al. 2009). Across their entire range, the Rocky Mountain Tailed Frogs are known to occur at elevations up to 2,590 m (8,500 ft), or approximately up to the treeline (Nussbaum et al. 1983, Maxell 2009).
Maximum elevation: 2,661 m (8,729 ft) on unnamed tributary to Halfway Creek in the Pioneer Mountains in Beaverhead County (B. Murdock; MTNHP 2007).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Non-migratory. Has no breeding migration (Daugherty 1982).
Rocky Mountain Tailed Frogs are found in and along small (< 4.5 m width), fast permanent forested streams with clear, cold water, cobble or boulder substrates, and little silt (Franz and Lee 1970, Franz 1971, Welsh 1990). In the Flathead area, larvae are found only in streams with temperature under 16 °C. They prefer fast streams, less than 14 ft wide, with substrate of slabby-flat bottomed rocks with little aquatic vegetation (Franz and Lee 1970).
Larvae feed mostly on diatoms, but also algae and small aquatic insects (Franz 1970b). Adults are opportunistic and forage mainly at night in forest near streams on a variety of aquatic and terrestrial invertebrates (Metter 1964b, Bury 1970).
In Montana, adults usually remain underwater hidden by rocks or debris and emerge at night or during humid weather from May to September to feed terrestrially along stream edges (Daugherty and Sheldon 1982a). Tadpoles cling to the undersides or tops of smooth rocks which lack periphyton or silt (Nussbaum et al. 1983). Adults are highly philopatric but are known to forage up to 75 m away from water in Montana (Daugherty and Sheldon 1982b, Maxell et al. 2009). However, they may range farther from water in wetter areas. Gomez and Anthony (1996) found them in pitfall traps 200 m from streams in the Oregon Cascades and Corn and Bury (1990) found juveniles and adults ranging more than 300 m from the nearest stream west of the Cascade Mountains in Oregon and Washington. At high elevations in Montana, adults and juveniles have been found to be active diurnally in warmer standing water bodies 50-75 m away from streams during warm dry weather (Maxell et al. 2009). American Dippers (Cinclus mexicanus
) have been documented predating on the closely related species Coastal Tailed Frog (Ascaphus truei
) (Morrissey and Olenick 2004).
In Montana, adults breed via internal fertilization in streams during August or September. Females store sperm overwinter (Metter 1964b) and ovipost eggs under large stones in areas with slight current the following June or July (Franz 1970a, Daugherty and Sheldon 1982a). Eggs hatch in August or September but remain in nest (under rocks in stream) until the yolk is consumed (October to November). Development of eggs under natural conditions is discussed by Franz (1970b). Tadpoles usually metamorphose in the third summer after hatching in July to September. In Montana, adults reproduce for the first time four or five years after metamorphosis (age 7-8) which is the latest of any North American amphibian. Females reproduce in alternate years thereafter (Daugherty 1979, Daugherty and Sheldon 1982a). Because of this species extremely philopatric nature, likely that there is very little gene flow between populations (Daugherty 1982).
The following was taken from the Status and Conservation section for the Rocky Mountain Tailed Frog account in Maxell et al. 2009
Rocky Mountain Tailed Frogs are widely distributed and common west of the Continental Divide in smaller streams that have adequate amounts of cobble substrates. Their status in the front ranges east of the Continental Divide is uncertain. Risk factors relevant to the viability of populations of this species are likely to include all the general risk factors described above (especially those which change stream morphology, and increase sedimentation and water temperature), with the exception of harvest and commerce. Individual studies that specifically identify risk factors or other issues relevant to the conservation of tailed frogs include the following. (1) Although the impacts of timber harvest have not been studied in Montana, numerous studies have documented the extirpation of Rocky Mountain Tailed Frogs at a number of locations in the Pacific Northwest as a result of increased sedimentation and water temperature resulting from timber harvest and associated road building activities (Metter 1964, Bury 1983, Bury and Corn 1988, Welsh and Lind 1988, Corn and Bury 1989, Corn and Bury 1990, Welsh 1990, Bull and Carter 1996a). Because Rocky Mountain Tailed Frogs are highly philopatric, have limited dispersal capabilities, and are apparently somewhat reliant on old growth forests, streams they have been extirpated from may not be recolonized for extensive periods of time after timber harvest activities (Metter 1967, Daugherty and Sheldon 1982a, Corn and Bury 1989, Welsh 1990). Furthermore, some of these same studies found that even if Rocky Mountain Tailed Frogs were still present after timber harvest their density and biomass were negatively affected. Additionally, density and biomass were lower in younger stands than older stands (e.g., Corn and Bury 1990, Welsh 1990, Gomez and Anthony 1996). A study in the Blue Mountains of Oregon provides evidence that stream buffers do provide protection for Rocky Mountain Tailed Frogs in drier forests similar to those found across much of Montana. Bull and Carter (1996a) found that the number of Rocky Mountain Tailed Frogs was best predicted by a combination of stream substrates and the presence of stream buffers. (2) Although the impacts of piscicides have not been formally investigated, anecdotal evidence from treated areas in Montana suggests they may have major population-level impacts on Rocky Mountain Tailed Frogs (Andrew Sheldon, University of Montana, personal communication). Fontenot et al. (1994) and McCoid and Bettoli (1996) recently reviewed the impacts of rotenone-containing piscicides on amphibians and found that the effects of rotenone on newly metamorphosed and adult amphibians varied with the degree of each species’ aquatic respiration and their likelihood of exiting treated water bodies. They found the range of lethal doses of rotenone-containing piscicides for amphibian larvae (0.1-0.580 mg/L) to overlap to a large extent with lethal doses for fish (0.0165-0.665 mg/L), and to be much lower than the concentrations commonly used in fisheries management (0.5-3.0 mg/L). The nontarget effects of another piscicide, antimycin, have apparently not been formally studied, but preliminary observations seem to indicate that antimycin is also toxic to amphibian larvae (Patla 1998b). Tailed frog larvae and adults both use aquatic respiration and adults are unlikely to exit treated water bodies depending on the time of day (Daugherty and Sheldon 1982b).
- Literature Cited AboveLegend: View Online Publication
- Adams, M.J. 1993. Summer nests of the tailed frog (Ascaphus truei) from the Oregon coast range. Northwestern Naturalist 74: 15-18.
- Bull, E.L. and B.E. Carter. 1996a. Tailed frogs: distribution, ecology, and association with timber harvest in northeastern Oregon. USDA Forest Service, Research Paper PNW-RP-497, Portland, Oregon. 17p.
- Bury, R.B. 1970. Food similarities in the tailed frog, Ascaphus truei, and the Olympic salamander, Rhyacotriton olympicus. Copeia 1970: 170-171.
- Bury, R.B. 1983. Differences in amphibian populations in logged and old growth redwood forest. Northwest Science. 57(3): 167-178.
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- Corn, P.S. and R.B. Bury. 1990. Sampling methods for terrestrial amphibians and reptiles. General Techinical Report PNW-GTR 256, USDA, Forest Service. 34 p.
- Daugherty, C.H. 1979. Population ecology and genetics of Ascaphus truei: an examination of gene flow and natural selection. Ph.D. dissertation, University of Montana. Missoula, MT. 143 pp.
- Daugherty, C.H. and A.L. Sheldon. 1982a. Age-determination, growth, and life history of a Montana population of the tailed frog Ascaphus truei. Herpetologica 38(4): 461-468.
- Daugherty, C.H. and A.L. Sheldon. 1982b. Age specific movement patterns of the frog Ascaphus truei. Herpetologica 38(4):468-474.
- Fontenot, L.W., G.P. Noblet and S.G. Platt. 1994. Rotenone hazards to amphibians and reptiles. Herpetological Review 25(4):150-156.
- Franz, R. 1970a. Egg development of the tailed frog under natural conditions. Bulletin of the Maryland Herpetological Society 6(2): 27-30.
- Franz, R. 1970b. Food of larval tailed frogs. Bulletin of the Maryland Herpetological Society 6: 49-51.
- Franz, R. 1971. Notes on the distribution and ecology of the herpetofauna of northwestern Montana. Bulletin of the Maryland Herpetological Society 7: 1-10.
- Franz, R. and D.S. Lee. 1970. The ecological and biogeographical distribution of the tailed frog, Ascaphus truei, in the Flathead River drainage of northwestern Montana. Bulletin of the Maryland Herpetological Society 6: 62-73.
- Gomez, D.M. and R.G. Anthony, R. G. 1996. Amphibian and reptile abundance in riparian and upslope areas of five forest types in Western Oregon. Northwest Science 70(2):109-119.
- Maxell, B.A., P. Hendricks, M.T. Gates, and S. Lenard. 2009. Montana amphibian and reptile status assessment, literature review, and conservation plan, June 2009. Montana Natural Heritage Program. Helena, MT. 643 p.
- McCoid, M.J. and P.W. Bettoli. 1996. Additional evidence for rotenone hazards to turtles and amphibians. Herpetological Review 27(2): 70-71.
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- Additional ReferencesLegend: View Online Publication
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