Frog of the Week

Rocky Mountain Tailed Frog (Ascaphus montanus)

photo by Ryan Killackey

Common Name: Rocky Mountain Tailed Frog, Inland Tailed Frog, and Eastern Tailed Frog
Scientific Name: Ascaphus montanus
Family: Ascaphidae – Tailed Frog Family
Locations: Canada and the United States
US Locations: Idaho, Montana, Oregon, and Washington
Size: 1 – 2 inches (30 – 50 mm)

As the name suggests, the Rocky Mountain Tailed Frog is found near the Rocky Mountains. They inhabit fast flowing, cold streams and the areas surround them in old growth forests. The tadpoles have specialized suctions in their months, allowing them to cling to rocks in the fast moving streams.

The tailed frogs have an unusual reproduction style. The males of the species have a tail-like appendage that they use to internally fertilize the females. There is only a handful of frogs and toads that use internal fertilization. There is only one other frog that has a tail in their adult form, the Coastal Tailed Frog, a close relative.

The frogs mate in early fall but the female doesn’t lay her eggs until mid summer of the next year, when the water flow of the stream lessens. The female lays between 45 – 75 eggs. Then the tadpoles take 3 years to complete their metamorphism.

Besides the tail aspects of its reproduction, the Rocky Mountain Tailed Frog is bizarre in the fact that it lacks a tongue and vocal cord. This makes it impossible for the frogs to make noise and do breeding calls.

Rocky Mountain Tailed Frog
photos by Forest Service Northern Region

The Rocky Mountain Tailed Frog is an ancient frog species as it has 9 presacral vertebrae while most have 8 or fewer. This resembles more of the earlier frog.

The International Union for the Conservation of Nature (IUCN) Red List assesses the frog as Least Concern for Extinction due to their large population and decent range.

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