Critters of North Idaho: Meet the Idaho giant salamander

If you’ve been reading Critters of North Idaho for a while, you might remember when I wrote about Idaho’s smallest salamander, the 4- to 5-inch Coeur d’Alene salamander.

At the other end of the spectrum is a giant. Residing in the forested watersheds of Lake Coeur d’Alene and other waterways of North Idaho and western Montana, the Idaho giant salamander — officially called “Dicamptodon aterrimus” — is the state amphibian of Idaho.

Just how giant is an Idaho giant salamander? Adults range in size from 7 to 13 inches. These amphibians possess what has been described as light or tan bronze marbling overlaying dark brown or black skin. The larger-than-average size, robust body and jaws of adult Idahos help them prey on a variety of animals, including insects and other invertebrates, mice, shrews, other salamanders and even small snakes. You’re unlikely to see one of these salamanders on the hunt, however, because they’re nocturnal. They prefer warm, rainy nights.

Most adults of this species can be found under logs, bark or rocks in coniferous forests about 7,086 feet above sea level. Like most amphibians, their eggs are incapable of retaining the water they need to survive. That’s why, in the spring and fall, pregnant salamanders must locate the calm, cool headwaters of a clear, cool mountain stream, lake or pond in which to deposit 135 to 200 eggs.

The mother faithfully guards her eggs. For seven moths, she won’t leave her post even to eat. This might be one reason why these salamanders only lay eggs every other year.

Upon hatching, young salamanders enter an intermediate larvae stage, a stop between egg and adult. Larvae are born for life in the water, where they spend the first part of their lives. They come ready to swim, complete with short, bushy gills and tail fins.

This is when things can get weird.

While most Idaho giant salamanders make the full transformation into adulthood, some do not. Instead, they become old enough to have larvae of their own without leaving the water behind and getting rid of their gills and tail fins. This rare phenomenon is called paedomorphosis, and some species of salamanders are the only animals capable of it.

In the water, larvae (and the adults that do not become terrestrial) are voracious predators. They are ambush hunters, waiting for small fish, tadpoles, other young salamanders or basically any other aquatic organism that fits in their mouths that swims too close.

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Christian Ryan may be reached at animaladventures1314@gmail.com.