The Larch Mountain Salamander (Plethodon larselli) is a small, rare amphibian that is endemic to Washington and Oregon. In appearance, it is superficially similar to several other salamander species in the region, such as the Western Red-backed Salamander.
I got to see my first Larch Mountain Salamander back in October, when I hiked up to Silver Star Mountain in southern Washington. I was very excited to find this species.
Two features that easily distinguish the Larch Mountain Salamander are the ragged edge of the dorsal stripe– which can be a orange, yellowish, red, or chestnut color– and the tiny outer toe on the back foot. This toe is just a nubbin, about 1/4 the length of its neighboring toe. Check out the photo at right. The red arrows point to the outer toes of the hind feet.
A Larch Mountain Salamander can be up to 4.1 in (105 mm) in total length. The ventral (belly) side is pink like salmon flesh or reddish. There are many tiny white flecks on the sides. These extend almost all the way up to the dorsal stripe. You can see this clearly in the photo at right.
This salamander is rare because it has a small geographic range and its habitat is distributed in patches across the landscape.
Populations of the Larch Mountain Salamander exist on both sides of the Columbia River Gorge, with some populations located further north in the Washington Cascades (King and Kittitas counties). They occur at elevations from 160 to 4,100 feet (50-1250 m).
Strong genetic differences between populations separated by the Columbia Gorge indicate that the big river probably acts as a barrier to movement for these salamanders.
Talus slopes in forested areas are the preferred habitat of this species. These rocky habitats are usually away from streams and can be somewhat dry, especially in the summer. In the driest and coldest months, Larch Mountain Salamanders retreat into deep crevices beneath the talus. They are active at the surface in spring and autumn, when conditions are cool and wet.
Larch Mountain Salamanders are also sometimes found under piles of decaying wood in mature forests and among the volcanic rubble at the entrances to lava tubes.
The geological and environmental conditions that make for great Larch Mountain Salamander habitat overlap in a very patchy way across the species’ range. Like many salamanders, Larch Mountain Salamanders aren’t able to travel long distances between habitat patches. So populations are isolated from each other, existing in little habitat ‘islands.’
If disturbed by a predator, such as a shrew or snake (or a curious human), a Larch Mountain Salamander will often coil up, so that it resembles a millipede. Millipedes excrete nasty chemicals that taste terrible, so perhaps the salamander’s behavior is a form of defensive mimicry. Several other salamanders in the Pacific Northwest show this same behavior.
If disturbed enough, the salamander will uncoil and coil itself rapidly, causing its little body to fling off in a random direction. This confuses the would-be predator and allows the salamander to escape.
The Larch Mountain Salamander is considered a ‘Sensitive’ species in both Washington and Oregon. Habitat loss is the greatest threat to the long-term persistence of this amphibian. Human activities that destroy salamander habitat include timber harvesting, road construction, mining, and the application of chemical toxins, such as herbicides.