Red-backed salamander: a forest-floor animal with no lungs

Under a rotting log in an eastern hardwood forest lives a slim salamander, a few inches long, with a rust-red stripe down its back. As an adult, it has no lungs at all. The Animal Diversity Web, a University of Michigan database, says the red-backed salamander (Plethodon cinereus) breathes through its moist skin. It is doing that right now, quietly, under the log.

That one fact shapes almost everything about its life. Breathing through the skin ties the animal to damp places, so the red-backed salamander stays where the ground stays moist. It hunts in leaf litter, shelters under logs and rocks, and never has to visit a pond, because its eggs hatch straight into tiny salamanders on land.

This article walks through how skin breathing works, what researchers know (and do not know) about how lungs were lost, and what a lungless life looks like on a forest floor. Most facts come from a journal paper and from university and zoo pages. When a number comes from a single source, we say so.

Meet the red-backed salamander

The red-backed salamander lives in the deciduous (leaf-dropping) forests of eastern North America. The Animal Diversity Web places it from Missouri east, south to North Carolina and north to Minnesota and southern Quebec. Adults are small: the same source gives 5.7 to 12.7 centimeters (about 2.2 to 5 inches) and an average weight of half a gram, lighter than a paper clip.

Both color forms have a mottled white and gray belly, according to the Animal Diversity Web. The Toronto Zoo guide adds that all-red individuals are very rare.

How breathing through skin works

Breathing means getting oxygen in and carbon dioxide out. Most land animals do that swap in their lungs. The red-backed salamander does it through its skin and the lining of its mouth. A 2022 Science Advances paper by Zachary Lewis, Ryan Kerney and James Hanken says that all adult plethodontid salamanders are lungless and use skin and the lining of the mouth and throat for gas exchange. The University of Wisconsin-Green Bay biodiversity page says the same about this species.

The sources tie that body plan straight to the animal’s choice of home. The Toronto Zoo guide says that because all respiration happens through the skin, the red-back is restricted to moist environments. The Wisconsin page calls the species extremely sensitive to dry or acid conditions. Picture a door that doubles as your lungs: it works when it is open and damp, and it jams when it dries out.

A lungless salamander is not a water animal in disguise. It simply moves the air-to-blood handoff from an inner organ to the outer surface.

Where did the lungs go?

Here the story turns into a puzzle. The Lewis paper reports that lungs have been lost independently in several groups of living amphibians (the authors count four), and that plethodontids make up more than two-thirds of living salamander diversity. The red-backed salamander is the main animal in the study.

What they found is oddly tidy. The embryos begin building lungs. Small lung buds form, but they regress, a process driven by programmed cell death, before the animal hatches. The authors compared this with the axolotl, a salamander that keeps its lungs, and conclude that the genetic pathways for building lungs are at least partly still in place in the lungless group.

How old is the lungless lifestyle? The paper’s abstract says at least 25 and possibly more than 60 million years. The lower figure matches the age of the oldest plethodontid fossils the authors mention, so the true date remains uncertain. As for why lungs were lost, the paper does not pick an answer. It calls the adaptive reasons and ecological setting highly debated. Anyone who gives you a neat one-line explanation is ahead of the researchers.

What a lungless life looks like in practice

The table below pulls together what the Animal Diversity Web (and, where noted, the Toronto Zoo) report about how a red-backed salamander handles the year.

A few more details. Females and males reach sexual maturity at about two years, and the Animal Diversity Web says males mate every year while females mate every other year. Snakes, blue jays, American robins, American crows, raccoons, striped skunks, Virginia opossums and large frogs all eat red-backed salamanders. Egg counts differ by source: three to fourteen in the Animal Diversity Web, six to ten for Ontario in the Toronto Zoo guide.

Common mistakes and mix-ups

Mix-up: it is a small lizard. A slim body and a stripe can fool you, and the Five-lined skink makes the comparison tempting. But the red-backed salamander is an amphibian. Its skin is moist and doubles as a breathing surface.

Mix-up: lungless means it cannot breathe air. It breathes air perfectly well. Oxygen simply enters through damp skin and mouth lining instead of lungs.

Myth: redbacks and leadbacks are different species. The Animal Diversity Web describes them as two color forms of one species, differing in whether the back stripe is present.

Mistake: all salamanders are lungless. They are not. The Axolotl is the lunged animal the 2022 paper uses as its comparison.

Mistake: a forest salamander needs a pond. This one needs none. Its whole life cycle is on land, unlike the Spotted salamander, which walks to a breeding pool each spring.

Conservation status

The red-backed salamander is listed as Least Concern on the IUCN Red List of Threatened Species. That is the category as distributed by GBIF, the Global Biodiversity Information Facility, and we checked it on November 9, 2026. Least Concern means the species was evaluated and does not meet the criteria for a threatened or near-threatened category.

Least Concern is not the same as no worries. The Animal Diversity Web calls the species common across most of its range, and the main threat it names is high soil acidity from human causes such as acid rain, which could affect the animal in the future. The Wisconsin page says the species is extremely sensitive to dry or acid conditions, which limits where it can live. We have no confirmed population trend, because none of our sources states one.

Categories are reviewed and can change, and the copy GBIF distributes can trail the IUCN website by some months, which is why we print the date we checked. GBIF’s copy does not give the year of the IUCN assessment, so we do not state one.