By: Bridget Hudnall, 2024-2025 SPARCnet RaMP Mentee

Have you ever met a red-backed salamander? It is one of the most abundant vertebrates in the forests of northeastern North America, lurking just out of sight under logs and leaf litter. And in the great numbers of these salamanders, many colors can be found.

Despite the fact that the common name of this salamander species is the “Eastern Red-backed Salamander,” many members of the species do not actually have red backs. These salamanders are known for having two different colorations: the “red-backed” color variant, which has a red back, and the less common “lead-backed” color variant, which has a gray back. However, this is only scratching the surface of the many possible colorations seen in red-backed salamanders. 

I am Bridget Hudnall, a postbaccalaureate mentee in the SPARCnet RaMP program. I started my term during July 2024, and since then, I have been interested in differences between the different color variants of red-backed salamanders. As it turns out, there is more to these salamanders and their colors than meets the eye.

However, I am getting ahead of myself. Just a year before joining SPARCnet RaMP, salamanders were hardly on my mind at all. It was only in November 2023 that I saw a salamander in the wild for the first time ever, and since then, I have had a great fascination with these adorable tailed amphibians. I even moved over 1,000 miles to Michigan for the opportunity to work with them.

Shortly after arriving in Michigan in June 2024, I had my first of many encounters with an eastern red-backed salamander(Plethodon cinereus). While walking in a forested area, I turned over a log on the forest floor and noticed a tiny tail poking out from under the leaf litter. Under the leaves was this juvenile salamander. It showed the typical coloration expected of this species: dark gray with a reddish stripe running down the back.

Fig. 1: An image of the standard striped or “red-backed” morph of /Plethodon cinereus/, found in Michigan
Fig. 1: An image of the standard striped or “red-backed” morph of /Plethodon cinereus/, found in Michigan

Continuing on my walk, I found more Red-backed Salamanders under logs in the forest, a couple of which showed the “lead-backed” coloration: all gray with no red stripe.

Fig. 2: An image of the unstriped or “lead-backed” morph of /P. cinereus/, found in Michigan
Fig. 2: An image of the unstriped or “lead-backed” morph of /P. cinereus/, found in Michigan

These were the two colorations I had come to expect for this species, but it did not take long for me to expand my horizons. In early July 2024, I attended the SPARCnet RaMP “bootcamp” at Mountain Lake Biological Station in Virginia. There, while hiking in a gorgeous Appalachian forest, I encountered this individual.

Fig. 3: An image of a salamander found in the mountains of Virginia. It resembles the red-backed morph, but its stripe is cream-colored.
Fig. 3: An image of a salamander found in the mountains of Virginia. It resembles the red-backed morph, but its stripe is cream-colored.

It almost looked like a typical red-backed salamander, but its stripe was cream-colored instead of red. In September, I found a similar-looking individual in Bruce Peninsula National Park in Ontario, Canada, hundreds of miles north of Virginia.

Fig. 4: An image of a salamander found in Ontario, Canada. It resembles the red-backed morph, but its stripe is pale gold.
Fig. 4: An image of a salamander found in Ontario, Canada. It resembles the red-backed morph, but its stripe is pale gold.

The existence of pale-striped individuals in such distant populations led me to wonder just how much variation there really is in this species.

As I continued to examine the differences between the two morphs, I noticed that lead-backed salamanders often displayed unique coloration as well. Take this individual, for example.

Fig. 5: An image of a salamander found in Michigan. It resembles the “lead-backed” morph, but it has two small red spots on its tail and tiny gold flecks on its back.
Fig. 5: An image of a salamander found in Michigan. It resembles the “lead-backed” morph, but it has two small red spots on its tail and tiny gold flecks on its back.

Despite being a “lead-back,” its back and tail are covered in tiny gold flecks, and two small reddish patches are faintly visible on the tail. This is an example of iridistic coloration, which is seen in the form of iridescent speckling or a general iridescent sheen. Meanwhile, the red spots on the tail suggest that the lead-backed and red-backed morphs are not as binary as expected.

Besides the colors I have already shown, there is another noteworthy color variant seen in Red-backed Salamanders: the all-red, or erythristic, variant.

Fig. 6: An image of a salamander found in Massachusetts. It is red all over with a few black spots on its tail. Photo by Madelyn Chartier.
Fig. 6: An image of a salamander found in Massachusetts. It is red all over with a few black spots on its tail. Photo by Madelyn Chartier.

Erythristic individuals are often observed in areas with high populations of eastern newts (Notophthalmus viridescens). Eastern newts are poisonous, and their juvenile forms, known as efts, are bright red, which advertises to potential predators that they are not good to eat. Therefore, the bright coloration of erythristic red-backed salamanders may potentially trick predators into thinking that they are actually poisonous newts, allowing them to avoid being eaten.

The color variations that I have shown so far are what I have personally observed throughout my year of studying red-backed salamanders, but there are still many more potential variations that I have not seen yet. These salamanders can be leucistic (pale white or pink), albino (similar to the leucistic ones but have red eyes), and amelanistic (pale but can retain the red stripe on its back). All of these color variants have been observed in multiple localities throughout the salamander’s range and may be more common than previously thought.

Red-backed salamanders don’t just come in many colors; they are also fluorescent. Shining a light on them can cause them to glow in bright green and blue colors. Given that these salamanders are nocturnal and spend most of their time underground, why do they have these unique colorations? Despite the fact that red-backed salamanders are a well-studied species, this question still puzzles researchers to this day. It goes to show that there is always more to discover about our world and the creatures that inhabit it.

While this diversity in coloration may be surprising to some, it actually reflects a rather common trend in biology, which is that things rarely fit into neat categories. Living beings are not easily sorted into discrete boxes, such as male and female or red-backed and lead-backed. Nature is more complex than that. All that I’ve described so far only covers the color variation in a single species of salamander; imagine the variation among the hundreds of salamander species in the world, or even among all amphibians. And while curious people and scientists continue to ask and answer big questions about how our world works, we will learn more about varied salamander colors!

Salamander of Many Colors