The Red-backed Salamander



Story shared by Kiley Briggs

Meet the Eastern Red-backed Salamander (Plethodon cinereus). If you’ve ever rolled over a rock or log in a northern New England hardwood forest there is a good chance you’ve already met. If you’re like me and look under almost every rock, log, or piece cover you’re capable of lifting, there’s a good chance you’ve met countless times, maybe thousands. For those of us interested in herpetology, becoming bored with Eastern Red-backed Salamanders is incredibly easy; Red-backed Salamanders seem to be under every rock, log, and rotting carpet in the woods and we just get used to them. I think the last time I ran excitedly towards someone yelling that they’d found a redback, I might have been twelve years old. There is a lot to appreciate about the species, though, so I’d like to spend a few minutes reminding you (and myself) how awesome these little salamanders are and why they deserve our appreciation. Let’s start with the very same reason why many of us got bored with the species to begin with: their abundance.

Red-backed Salamander

In many hardwood forests, the abundance of Eastern Red-backed Salamanders borders on absurd. Given adequate leaf litter, moist soil, and neutral pH, these little buggers can be everywhere. One widely-cited study out of New Hampshire found that if you add up the mass of every salamander, bird, and small mammal in the forest, the salamanders account for as much mass as all the small mammals put together and more than twice that of all the birds. While those numbers include ALL species of salamander, Red-backed Salamanders, which only weigh about 1.5 grams each, accounted for about 93.5% of the salamander biomass. In short, Eastern Red-backed Salamanders are easily the most abundant vertebrate in many northeastern hardwood forests and their combined mass dwarfs that of any bird or rodent. Not only are they incredibly common, but they have some very unusual characteristics, even for an amphibian.

While all salamanders have larvae, Red-backed Salamanders (and the closely-related Slimy Salamander) are the only amphibians in northern New England that have completely severed their connection to pools of water. Their eggs are laid on land and the larvae go through the entire aquatic larval stage inside the eggs, hatching as tiny terrestrial salamanders that could fit comfortably on a pencil eraser. This process, called direct development, isn’t unique in the amphibian world, but skipping an aquatic stage is not the norm. A somewhat more normal, yet equally fascinating aspect of Red-backed Salamander biology is the female’s defense of her eggs.

Red-backed Salamander

Females care for and protect their eggs, aggressively lunging at, biting, and grappling with predators, including other Red-backed Salamanders. Guardianship over the eggs extends beyond just physical defense from predators, but also from infection. Contact between the mother and her eggs may help protect them from fungal infection by transmitting anti-fungal molecules from the skin to the eggs themselves, much in the way that mammalian mothers protect their unborn young with their own immune systems. Red-backed Salamanders aren’t just protective of their young, though; they are also fiercely protective of their territories.

While we, the log-flippers, often see more than one Red-backed Salamander sharing the same space, the species is actually highly territorial. Males defend their territories from other males and mark them with scat in the same way coyotes and other mammals do. Females can tell which males have good territories based on the smell of their excrement and choose which males to mate with accordingly. No joke, but the aptly named “Sexy Feces Hypothesis” explains that females can determine the quality of a male’s territory by “smelling” his excrement to see what he’s been eating; scat the smells like termites is good, scat smelling like ants is bad and indicates a poor territory. I see far too many flipped rocks and logs left upside down with residing salamanders left to find a new home, but with so many Red-backed neighbors, a displaced salamander might have more difficulty than you’d imagine carving out a new territory.

So, why did I put the word “smelling” in quotations in the last paragraph? Red-backed Salamanders don’t have lungs, can’t inhale, and their process of smelling is quite different from ours. Instead, they have a small groove connecting each nostril to their lip (called a nasolabial groove) that allows chemicals to diffuse into their nostril where highly sensitive receptors give the salamander information about chemical composition. Without lungs the Red-backed Salamander, and other species in the Plethodontidae family, respire entirely through their skin and must remain moist in order to do so. While all amphibians can respire through their skin, the vast majority also have lungs or external gills to aid with respiration and the reason Plethodontid salamanders evolved away from lungs remains a bit of a mystery.

A major advantage Red-backed Salamanders have is that they can regrow any limb, an ability that inspires current medical research. Losing a tail is a fairly common defense salamanders use against predators and may save the salamander’s life. After detaching, the tail will continue to wriggle and writhe around, distracting predators while the salamander escapes. Losing the tail is bad news because the tail is where the salamander stores energy reserves, but the loss and subsequent need to rebuild those fat stores is a lot better than being eaten.

Red-backed Salamander

If you still can’t get excited about Red-backed Salamanders, I need to point out how incredibly variable the species is. Sure, most of them are gray or black with a red back and a “salt and pepper” belly, but there are also a lot of funky ones out there. Many are missing the red back and are called “leadbacks”, some are solid red, some are red with black spots, and some have random colors on their back instead of red. I’ve seen ones with gold, yellow, silver, and kind of greenish backs and am delighted every time I find a new variation. The oddballs are common enough, especially in some areas, that you never know what you’ll find under that next rotten log. If you use my photo collection as a guide, you won’t have any idea what a Red-backed Salamander is even supposed to look like.

In selecting photos for this article, I was reminded that I too take Red-backed Salamanders for granted. I’m guilty of passing up good photo opportunities of the species I see the most often and, while I have dozens of high-quality photographs of much rarer salamanders, I realized I didn’t have any decent shots of Red-backed Salamanders with normal color. Red ones, black ones, and black-spotted ones, sure, but no normal ones. Venturing back into the woods mid-article to get the shots I needed of a regular Red-backed Salamander I’m almost ashamed to admit that I was hoping to find another oddball. Finding any Red-backed Salamanders at all proved much more challenging than expected, so I can honestly say that finding one in the fading light was genuinely exciting. For the first time in a long time, I felt like that 12-year old again gazing at a tiny lungless wonder.

Cheers to the Eastern Red-backed Salamander; the incredibly-abundant lungless salamander with no aquatic larvae that defends their young, their homes, chooses mates based on the smell of a male’s feces, can look like anything, and that can regrow any limb. You are awesome.