Eastern red-backed salamander (Plethodon cinereus) – photo: Dave Huth CC-BY-2.0
Life Under the Leaves
GET TO KNOW: Eastern red-backed salamanders
Eastern red-backed salamanders are tiny, delicate creatures that live in the damp leaf litter of the forest floor. Theirs is a life of hiding – under rocks and rotting logs – where they forage for insects and shelter from the sun.
FUN FACT: Red-backed salamanders have the ability to recognize close kin (most likely through scents) and often “take in” young relatives during dry seasons when food sources are scarce. In such cases, an adult accepts a related “homeless” juvenile into his foraging territory while still vigorously defending the territory against intruders.
They are slender, silent and skittish and rarely seen by the casual woodland hiker.
Male and female red-backed salamanders look alike and are generally less than four inches long. Juveniles are simply smaller versions of adults. The name “red-backed” derives from the common color pattern of a gray body with a prominent reddish stripe along the back and tail. However, many individuals are solid gray, and an occasional few are solid red.
Salamanders are amphibians, and as such, are cold-blooded vertebrates. It is a common misconception that all amphibians have two distinct life stages – a gilled aquatic (tadpole) stage and a lunged (adult) stage. In actuality, different amphibians exhibit very different life cycles. Some amphibians do have both a gilled and a lunged stage. However, some have only gills and live entirely in water. Some have only lungs and live on land. And just to confuse things, some have neither gills nor lungs. This last group breathes by absorbing oxygen through capillary action in moist skin. Perhaps the defining amphibian characteristic is a permeable skin that absorbs air, water and, unfortunately, contaminants. Their skin must stay moist at all times, and even human skin oils can hurt them. Red-backed salamanders belong to the “no gills / no lungs” group. They are members of the lung-less Plethodontidae salamander family that breathe through their skin and live out their entire life cycle on land.
HABITAT & LIFE CYCLE
Because they are dependent on a damp environment, summer droughts are difficult for these salamanders. Dry conditions confine them to small patches of moisture and limit foraging. The species has adapted to seasonal food deprivation by pulse feeding. This means they eat as much as possible during good conditions and store the extra energy for bad times. Red-backed salamanders store energy in fat cells within the tail. However, they also shed their tail if grabbed by a predator. So, while a new tail can grow back, the unfortunate salamander temporarily loses its precious energy reserve.
In their hidden world under the leaves, red-backed salamanders can live long lives (20+ years). While some fall prey to birds, snakes or small mammals, it is estimated these salamanders live, on average a good ten years. Over the seasons, they move in and out of loose partnerships, mark and vigorously defend fluid territories, and raise new generations. Within their range (Southeastern Canada, New England, the Great Lakes region, and the middle eastern US states) eastern red-backed salamanders can be very plentiful. In a healthy temperate forest, biologists estimate that the number of red-backed salamanders exceeds the total number of all birds and mammals combined. Dense populations may experience 2 to 3 of these salamanders per square meter. This hidden, but vast, army of salamanders is believed to play a vital role in the overall balance between insects, fungi, and plant matter within the forest ecosystem.
The social customs of red-backed salamanders are a bit difficult to study and observe. However, the ladies appear to be in control. The breeding cycle is an exhausting endeavor for the female, so she may be the one who moves about, checking out the guys, deciding when to breed or when to rest and live alone. She may come, she may stay – or she may just move on.
When a female is ready to choose a partner, she “sniffs” at territories. From scent markings and excrement, she can evaluate the identity and size of the male and the quality of his territory. She signals her interest by entering the territory. She is sure to be accepted as long as she doesn’t carry the scent of a different male. Partnerships are fluid, and breeding is not guaranteed. She may arrive in the fall and stay through winter hibernation -or not.
Regardless of when partnerships form, breeding takes place only in spring. The male performs a mating dance for the female before dropping an external sperm sac which the female must “pick-up”. The female then lays a small clutch of eggs (usually < 10) in a ground nest or log cavity. She curls herself around the eggs to keep them safe and moist for a two-month incubation period. During this time, she never leaves the eggs. She will snap and bite for defense, but she stays in place. Since she cannot forage, she relies entirely on the occasional passing bug and her stored energy reserve for survival. Though new hatchlings are fully formed, the mother guards for three additional weeks while they learn to forage. It is only when the tiny hatchlings leave home that the female also leaves to care for herself. She moves to establish an independent territory and she will rest until she is ready to repeat the cycle. Due to prolonged starvation during the incubation period, summer droughts and winter hibernation, a female may wait two years before breeding again.
Salamander populations are difficult to count and verify, but please do not upend logs to find them. You may destroy their territory markings and ruin microhabitats. Red-backed salamanders are confirmed as present in the watershed, but they are not specifically monitored. Their biggest threat is human destruction of forests.
FOTR directly monitors frogs and toads, aquatic macroinvertebrates, and fish. The results of FOTR’ monitoring surveys are shared with governing bodies, corporations and citizen groups to help identify and implement watershed protection goals. To participate in a FOTR species monitoring program, please see https://therouge.org/our-work/river-monitoring/