Tailed Frog (Ascaphus truei) 



Description: Adults are gray or brown with gray, brown, or occasionally yellow blotches. The 

 adult has a snout-vent length of 1 .5-2". The outer toe of the hind foot is broader than the 

 other toes, unlike other frogs and toads. Tailed frogs have no tympanum, while other frogs 

 and toads have a tympanum. The male has a bulbous "tail" which acts as an external 

 copulatory organ. Approximately 50 eggs are laid in rosary-like strings attached to the 

 underside of rocks. The tadpole (up to 2" snout-vent length) is unique in that it has a large 

 mouth modified into a sucker. 



Habitat and Habits: Tailed frogs are found in and along small, swift, cold mountain streams. In 

 the KNF, they were found in all districts and usually found with trout and sculpin species in 

 fast-moving, clear water with temperatures rarely exceeding 54' F. The distribution of frogs 

 within a stream was spotty and unpredictable. In a 20 mile stretch of Libby Creek, from 

 2850-4200 ft. elevation, frogs were found in 2 of 8 places when at least 100 meters of stream 

 was checked. In Grave Creek in the Whitefish Range, they were found in 2 tributary streams 

 of Grave Creek, both above 4000 ft. elevation, but were not found in Grave Creek itself. In 

 Deep Creek, also in the Whitefish Range, the species was not found in seemingly ideal 

 habitat, despite 6 checks along 1000 ft. of stream elevation . The highest elevations at which 

 the Tailed frog were found included Divide Creek at 5400 ft. and the outlet of Big Therriault 

 Lake at 5500 ft., both in the Whitefish Range. The lower limit was 2800 ft. along Libby 

 Creek. Both the upper and lower limits are probably dictated more by the nature of the 

 stream than by elevation itself. In the Cascade Mountains of Washington and Oregon, the 

 Tailed frog appears to be very sensitive to siltation and frequently disappears in and 

 downstream from clearcuts and water diversions (Bury, pers. comm.). Eggs are laid during 

 the early summer and take approximately 4 weeks to hatch. Tadpoles take 1-4 years to 

 metamorphose, depending on water temperature (Nussbaum et al. 1983; Metter 1967). 

 Sexual maturity in Montana is attained at ages 6-7 (Daugherty and Sheldon 1982) which is 

 the latest age for sexual maturity of any North American amphibian. 



Surveying: Tadpoles are frequently found while fish shocking. They may also be found by 

 turning over rocks in rapid water with a net held just downstream. Adults are best found by 

 walking up streams starting shortly after dark. 



Status: Apparently common in suitable habitat on the KNF and elsewhere in western Montana. 



Montana Natural Heritage Program rank: G5 S4 



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