One sunny morning in early October 2017, weeks before the first Autumn rains, I came across an unexpected sight: a strange-looking salamander out in the open, clambering over leaf litter in a dry creek bed. A narrow, sickly-looking creature about 3 inches long, with a short stubby tail and a flame-colored belly.
This was an Ensatina - and my very first Lungless Salamander encounter. These salamanders belong to Family Plethodontidae, a group comprising over 400 species. Plethodonts share a unique suite features that set them apart from other salamanders, including:
- Respiration through the skin, not lungs or gills;
- Special teeth on the roof of the mouth;
- Specialized glands for chemoreception;
- Ability to self-amputate the tail;
- Reproduction on land, not in water.
Not all Lungless Salamanders share all of these features - a few species (not in California) don't reproduce on land - but those who live in Roy's Redwoods do. We'll take a closer look at these features in a moment, but first allow me to introduce...
The Plethodonts of Roy's Redwoods
Of the six species of salamander present at Roy's Redwoods - California Giant, Pacific Newt, Rough-Skinned Newt, Arboreal, Ensatina, and California Slender - three belong to Family Plethodontidae.
As I was saying, the first Plethodont I met in Roy's Redwoods was the Ensatina (Ensatina eschscholtzii.) There are seven subspecies of Ensatina, each with their own unique appearance; those who live in Roy's Redwoods appear to be hybrids of Yellow-Eyed Ensatinas (E. eschscholtzii xanthoptica) and Monterey Ensatinas (E. eschscholtzii eschscholtzii.)
California Slender Salamander
The second Plethodont I met in Roy's Redwoods is also the smallest vertebrate in the forest: the California Slender Salamander (Batrachoseps attenuatus.) They might also be the most numerous vertebrate here. They're certainly the most common salamander.
The third species of Plethodont I met at Roy's Redwoods is the Arboreal Salamander (Aneides lugubris.) Salamanders in the genus Aneides are collectively known as Climbing Salamanders, and while this species does scale trees in search of prey, they can also be found under woody debris in the leaf litter.
All three species of Plethodonts at Roy's Redwoods - Ensatina, California Slender, and Arboreal - share the following five characteristics.
The Lungless Lifestyle
Unlike other salamanders, Plethodonts don't have lungs. Instead, they "breathe" through their skin and soft tissues in the mouth. Glistening, semi-translucent skin is characteristic of the Lungless Salamanders.
Because these salamanders have to stay well-hydrated, they stick to environments with high humidity. Preferred habitats include animal burrows, voids under woody debris, wet leaf litter, and spaces in rotting wood.
In addition to teeth in the usual places (on the upper and lower jaw,) Lungless Salamanders also have a set of teeth on their vomers - the bones that separate the left and right nasal cavities. They're known as vomerine teeth, and they protrude through the upper palate. Abundant vomerine teeth are what give Family Plethodontidae their name, from the Latin pletho (many) + dont (teeth.)
Vomerine teeth aren't used for chewing; instead, they prevent the salamander's prey from escaping before they're consumed. Some species of frogs also have vomerine teeth. You can see photographs of vomerine teeth on a Plethodont skull in this article (Figs. 5.46 and 5.47.)
Lungless Salamanders have a noticeable crease that runs down from the nostril to the upper lip. This is called the naso-labial groove, and it's lined with chemoreceptive glands that give these salamanders next-level sniffing skills, enabling them to track prey and avoid environmental hazards.
Tail autotomy is the ability to self-amputate one's tail, a feature these salamanders share with many species of lizards. The tail thrashes dramatically for a couple of minutes after it's lost, distracting predators and allowing the salamander to escape. Glands on the tails of many Plethodonts secrete a milky, toxic mucous that tastes terrible, numbs the mouth, and can be sticky enough to glue a predator's mouth shut for 48 hours.
Some Plethodonts, like Ensatinas, have a visible restriction at the base of the tail known as a basal tail restriction. Species with basal tail restriction have specialized anatomical features adapted to facilitate tail amputation; the restriction is always the site of amputation in these species. In species without basal tail restriction, like the California Slender Salamander, the tail may be self-amputated at any given point.
Self-amputation is a tactic of last resort, as it comes at a steep price to the salamander. Like many other California amphibians, Lungless Salamanders spend the hot, dry summers underground in a state of low metabolic activity known as aestivation. They rely on fat stored in their tails to get them through the long months of fasting, so while a dropped tail isn't immediately fatal, a tailless salamander might very well starve during aestivation.
That seems to be the case with the first Ensatina I encountered. Their tail is in the midst of regrowing, a process that takes about two years. They've depleted their fat stores over the summer months, so they've been forced above ground in broad daylight, warm and dry - well-nigh unthinkable behavior for a Plethodont - in search of prey to sustain them until the Autumn rains arrive.
The vast majority of Plethodonts, including all species in California, reproduce entirely on land. That might not seem like a big deal to mammals like us, but for amphibians, it's a remarkably clever adaptation that has allowed these creatures to inhabit realms beyond the reach of other species - like the canopy of a redwood forest.
Most amphibians share a familiar life story: Boy meets girl; girl likes boy's croaky song/protuberant eyes/plucky coloration; girls lays eggs in water and allows boy to fertilize them; tadpoles hatch out of eggs, develop legs and lungs, and eventually morph into semi-aquatic adults. But the Plethodonts have a different story.
When boy Plethodont meets girl Plethodont, he performs a courtship ritual, caressing her body with his own. If the courtship is successful, he deposits a packet of spermatozoa, which the girl Plethodont picks up with her cloaca. Fertilization occurs internally, and the female may delay fertilization until conditions are right. She chooses a humid, secluded nesting site, like a hollow log or animal burrow, where she lays her fertilized eggs. Most Plethodont mothers remain with their eggs until hatching, guarding them from predators and keeping them moist with her own body. Plethodont babies go through metamorphosis inside the egg, so when they hatch, they look like miniature adults.
Because they don't rely on an aquatic environment to reproduce, Plethodonts are able to live in territory that's out-of-bounds for other amphibians - places that are too far from a stream or pond. Clouded and Wandering Salamanders, close relatives of the Arboreal Salamander, have taken amphibian territory to new heights - literally. These salamanders can live in the canopy of Coast Redwood trees; a population might live for generations in a single tree without ever coming down to the ground.
As a group, Plethodonts share a number of traits that set them apart from other amphibians. And each of the three species in Roy's Redwoods has adaptations that set them apart from each other. Over the coming weeks, I'll be exploring each of these fascinating amphibians in depth.
Next week: Meet the Plethodonts: The Arboreal Salamander
Until then, step softly in the woods, and remember to be kind to small friends.
California Slender Salamander: