The tailed frog is so named because it looks like it has a tail, but the appendage isn't actually a tail at all. It is actually only found on males as it is an extension of the male cloaca. The coastal tailed frog is the only North American frog species that reproduces by internal fertilization. This is because the species lives in fast-flowing streams where external fertilization, as done by frogs living around calmer water, isn't such an effective strategy for reproduction.
This isn't the only adaptation the frogs have for life in fast-flowing water. California Herps writes, "To escape predators Tailed Frogs jump into the water, tuck in their limbs, and let the water quickly carry them downstream away from danger."
Even the tadpoles are specially adapted. "Tailed frogs have the only tadpole in Washington able to adhere to rocks in fast-flowing streams with a large sucker-like mouth," writes Washington State Department of Natural Resources.
There are just two species in the genus Ascaphus, and the "tail" is what makes them both stand out, as does the fact that they have more vertebrae than other frogs. They also don't have the ability to vocalize. But that's not such a big deal since they don't have an external ear membrane to help them hear anyway.
All in all, this is a very special species of frog that has become highly adapted to living among the rushing streams and rivers of the coastal Pacific Northwest.
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