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The coastal tailed frog (Ascaphus truei) is one of the most ancient species of frogs, belonging to the anuran suborder of Archeobatrachia and being closely related to the Leiopelmatidae family of New Zealand primitive frogs. The Ascaphidae family includes two species, A. truei and A. montanus, the Rocky Mountain tailed frog (Nielson, Lohman, and Sullivan 2001). The coastal tailed frog is native to the region of the Coast Ranges and the Cascade and Olympic Mountains extending from southwestern British Columbia through western Washington and Oregon to northwestern California. This species enjoys cooler temperate aquatic habitats, particularly fast-moving mountain streams, but they can be found in a wide range of elevations, from coastal sea level to alpine. The streams they inhabit must remain cool throughout the year (Brown 2005).
Coastal tailed frogs have various distinctive characteristics. A major identifying feature is the short cloacal “tail” of the males, which is actually a copulatory organ used for insemination of females in moving water. Ascaphus is only genus of frogs with such an organ for internal fertilization (EDGE 2016). Adults are somewhat smaller compared to most other frogs, typically ranging from 2.2 to 5.1 centimeters. In relation to overall body size, this species’ head is relatively large and flat and has a triangular mark between the eyes and the nose. Other identifying marks include webbed toes that are hardened at the tips, generally vertical pupils in their eyes, and the lack of tympanic membranes. The color of the dorsal area is variable, usually centering around a brown or dark green base. Male frogs are smaller than females and have greatly enlarged forearms during mating season. Tadpoles grow from around 11 mm after hatching to around 65 mm prior to adulthood. These tadpoles have sucker-like mouths that allow them to attach to rocks in the streambed for safety. A. truei is primarily a carnivore and insectivore, eating mostly insects and non-insect arthropods, as well as zooplankton and molluscs such as snails and slugs. Coastal tailed frogs can also eat algae and other forms of plant life. Predators include snakes, giant salamanders, shrews, fish such as trout and sculpins, and at least some species of birds (Adams and Pearl 2016; Potter 2012).