The red-backed salamander is a small terrestrial salamander, in total length, which usually lives in forested areas under rocks, logs, bark, and other debris. It is one of the most numerous salamanders throughout its range. The red-backed salamander exhibits color polymorphism and two color variations are common: the "red-backed" or "red-stripe" variety has a red dorsal stripe that tapers towards the tail, and the darker variety, known as the "lead-backed" phase, lacks most or all of the red pigmentation. The red-backed phase is not always red, but may actually be various other colors. Both morphs have speckled black and white bellies. Additional color anomalies of this species also exist, including iridistic, albino, leucistic, amelanistic, and melanistic anomalies. These color morphs are rarer than the red-backed, lead-backed, and erythristic morphs, but still have been reported with consistency among varying populations of this species. The skin of red-backed salamanders was found to contain Lysobacter gummosus, an epibioticbacterium that produces the chemical 2,4-diacetylphloroglucinol and inhibits the growth of certain pathogenic fungi.
Behavior
Antipredator behavior of P. cinereus was found to differ between the two color phases; the lead-backed phase has a tendency to run away from predators, whereas the red-backed phase often stays immobile and possibly exhibits aposematic coloration. Stress levels of each color phase were estimated by determining the ratio of neutrophil to lymphocyte cells in the blood, and the results suggest stress levels are higher in the lead-backed phase than in the red-backed phase. This may be a consequence of a higher predation risk experienced in the wild by the lead-backed phase, and may also mean lead-phase salamanders could be more vulnerable in captivity settings. Plethodon cinereus, like many plethodon species, exhibit homing behavior, with homing of females to their nests, as well as non-attending females and males to a home range. This allows for essential contact between a female and her eggs in order to ensure their survival, as well as for non-attending females and males to explore beyond the home range when under predation pressures, or searching for food or cover, and return to their home range if a more favorable microhabitat is not found.
Reproduction and biomass
Males and females of P. cinereus typically establish separate feeding and/or mating territories underneath rocks and logs. However, some red-backed salamanders are thought to engage in social monogamy, and may maintain codefended territories throughout their active periods. Breeding occurs in June and July. Females produce from four to 17 eggs in a year. The eggs hatch in 6 to 8 weeks. Not much is known about the dispersal of neonates, although neonates and juveniles are thought to be philopatric.The species largely consumes invertebrates and other detritus dwellers. In some areas with good habitat, these salamanders are so numerous, their population densities may surpass 1,000 individuals per acre. Pokagon State Park in Indiana is one such place. As in many Plethodon species, female red-backed salamanders have the ability to store sperm as spermatophore, and have been evidenced in doing so up to eight months prior to the oviposition period in June and July. Sperm or spermatophores are not retained following the oviposition period.
