Northwestern Salamanders are dark brown, gray, or black above and a lighter brown below. Like many other Mole Salamanders (Ambystomatidae) they can be fairly large, reaching maximum sizes of up to 8.5 inches. A rounded glandular ridge forms along the upper edge on the tail. They have large, conspicuous parotoid glands immediately behind the eyes. In the northwestern part of their range some individuals have small, light yellow to cream colored flecks on their upper side. This, along with some other differences, has been used to designate separate subspecies, with A. g. decorticatum possessing spots and A. g. gracile lacking them. However, these geographic differences have not been been found to be sufficiently consistent to warrant subspecies designations. The Northwestern Salamander breeds in permanent or semi-permanent waters, from small ponds to lakes and sometimes in the quiet pools of slow moving streams. Breeding takes place between January and August with the exact timing depending on elevation and latitude (the higher up or more to the north the later they breed). The aquatic larvae take at least a year to develop and over two years in high altitude sites. Neoteny, where larvae do not transform (metamorphose) but nevertheless become sexually mature, frequently occurs in high altitude populations. Such individuals can reach lengths of 10 inches or more. Populations of the Northwestern Salamander can be found as high as 10,000 ft. in the Cascade Mountains.