The Idaho giant salamander is the darkest and most intricately blotched of the giant salamanders. They vary between brown, purple, tan, grey, and a copperish color.
Tiger salamanders and Idaho giant salamanders have superficial resemblance pertaining to size and shape, but the
costal grooves and foot
tubercles are significantly different between the two species. This salamander has a defining thick head and body and a fourth toe on the hind foot with only three segments. Adults are typically 20 cm (7.8 inches) in length but often vary between 7 and 11.75 inches long and may be observed around 13 inches at maximum length. Small external gills adapted for small stream living can be found on their larvae. Their larvae are usually tan with yellow blotches over their dermis. They can undergo
paedomorphosis, but the ratio of terrestrial adults to paedomorphic adults is unknown due to sampling biases (most studies on the salamander are conducted in streams, where terrestrial adults are unlikely to be found). ==Distribution==