Rocky Mountain Tailed Frog - Ascaphus montanus
Tailed Frogs, Pair - Ascaphus montanus
Global Rank:
G4
State Rank:
S4
Agency Status
USFWS:
none
USFS:
none
BLM:
none
CFWCS Tier:
2
General Description
Adults are gray or brown with gray, brown, or occasionally yellow blotches; the skin has a distinctly bumpy texture. Adult body length is 1.5 to 2 inches. The outer tow of the hind foot is broader than the other toes. Tailed frogs have no external ear drum. The male has a bulbous "tail" that acts as a penis. Eggs and Tadpoles: Approximately 50 eggs are laid in rosary-like strings attached to the underside of rocks. The tadpole (up to 2 inches long) is unique in that it has a large mouth modified into a sucker; color is variable.
Diagnostic Characteristics
No other frog or toad has the outer toe of the hind foot broader than the other toes; all other frogs and toads have external ear drums.
Distribution
Montana Range
Migration
Nonmigratory. Has no breeding migration (Daugherty 1982).
Habitat
Tailed frogs are found in and along small, swift, cold mountain streams. Eggs are laid during late summer and take approximately 4 weeks to hatch. Tadpoles take 1 - 4 years to metamorphose, depending on water temperature. Sexual maturity in Montana is attained at 6 or 7 years of age (the latest of any North American amphibian) (FWP). Forested streams. In Flathead area, larv found only in streams w/ temp <16 C. Prefer fast streams, <14 ft wide, w/ substrate of slabby-flat bottomed rocks with little aquatic vegetation (Franz and Lee 1970).
Food Habits
Larva feed almost exclusively on diatoms, though also pollen (Metter 1964, Franz 1970) Ad.: opportunistic; forage at night in forest near streams. Prey on invertebrates, mainly terres. but also aquatic forms (Metter 1964, Bury 1970, Daugherty 1982).
Ecology
Low repro potential: repro maturity age 7-8; 2 yr cycle w/ 1st clutch at age 9 (Daugherty 1982). Extremely philopatric; pro- bably very little gene flow between populations (Daugherty 1982).
Reproductive Characteristics
Mate Aug-Sep; sperm stored overwinter (Metter 1964). Ovipost late Jun-Jul; hatch Aug-Sep but remain in nest (under rocks in stream) until yolk is consumed, Oct-Nov or later. Meta- morph. Jul-Sep of yr 4 (ca. 60 days required) (Daugherty 1979). Development of eggs under natural conditions is discussed by Franz (1970).
Citations & Sources
- 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. 143 pp.
- 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. Bul. MD Herpetological Society 6:62-73.
- Maxell, B. A., J. K. Werner, P. Hendricks, and D. L. Flath. 2003. Herpetology in Montana: a history, status summary, checklists, dichotomous keys, accounts for native, potentially native, and exotic species, and indexed bibliography. Northwest Fauna Number 5. 138 p.