The red-backed salamander (Plethodon cinereus) is a small, hardy woodland salamander species in the family Plethodontidae. The species inhabits wooded slopes in eastern North America, west to Missouri, south to North Carolina, and north from southern Quebec and the Maritime provinces in Canada to Minnesota. It is also known as the redback salamander, eastern red-backed salamander, or the northern red-backed salamander to distinguish it from the southern red-backed salamander (Plethodon serratus ). It is one of 56 species in the genus Plethodon. This article delves into the dietary habits of this abundant and ecologically significant amphibian.
General Overview of the Red-Backed Salamander
The red-backed salamander is a small terrestrial salamander, 5.7-10.0 cm (2.2-3.9 in) in total length (including tail), which usually lives in forested areas under rocks, logs, bark, and other debris. It is one of the most numerous salamanders throughout its range. Salamanders are so secretive that most people never encounter them! But because of their sensitive skin and specific habitat requirements, these shy creatures can tell us a lot about the health of our environment.
All salamanders belong to the amphibian order Caudata, from the Latin word for "tailed." Newts and mudpuppies are also types of salamanders.
Because of their slender bodies and long tails, salamanders look somewhat like lizards, so people often confuse the two. But lizards are reptiles, whereas salamanders are amphibians like frogs and toads. Lizards have scales and claws; salamanders do not. Lizards typically have dry skin; most salamanders stay moist, and many of them use their wet skin as a surface through which to breathe.
Dietary Composition
Red-backed salamanders are mostly insectivorous, but prey on a wide assortment of other small invertebrates including isopods, millipedes, centipedes, pseudoscorpions, harvestmen, spiders, and gastropods. They largely consume invertebrates and other detritus dwellers. On one occasion an individual was found to have cannibalized a P. cinereus embryo.
Read also: The "Gray Ghost" Raptor
Salamanders eat many small animals, from insects to spiders to worms. They consume several creatures that people consider pests including slugs, mosquito larvae, and flies. They will also sometimes eat other salamanders.
Ecological Role and Diet
Research indicates that because of their abundance, red-backed salamanders hold pivotal roles in their ecosystems, influencing a forest’s fungal communities. Fungi break down organic matter like fallen leaves, logs, and dead organisms. If nothing were to rot, the forest would soon starve. Red-backed salamanders feed on a wide variety of invertebrates like ants, spiders, centipedes, beetles, snails, and termites - many of which graze on fungus.
Influence of Color Morphs on Diet
The two primary P. cinereus color morphs also differ in diet. The prevalence of certain prey taxa and the overall diversity and quality of prey items have been observed to differ seasonally between the two morphs in the spring and autumn when surface activity is greatest. The diets of striped and unstriped P. cinereus differ the most in the spring and fall seasons. The striped salamanders have a red-colored dorsal band that runs from the head/neck to their tail, and the unstriped ones lack this red stripe and are instead totally black. These salamanders are at the surface the most during these seasons. Contrasting diets during the fall and spring are due to differences in two types of prey consumed during this time.
Some studies have suggested that the unstriped morph has adapted to be better suited for drier and warmer conditions explaining the differences in diets. Unstriped morphs are less aggressive and less likely to hold territories because they are more well suited to find a territory that these striped salamanders are less adapted to withstand. The unstriped salamanders can forage in drier leaf litter, so they do not need to protect their territory to the extent that striped morphs do. The less pressure the unstriped salamander feels to hold territory does change what type of access of prey it has access to compared to the striped salamander during the drier months.
Striped salamanders defend territories underneath objects such as rocks and logs when the conditions are dry. During these dry conditions, arthropods are forced to hide in these same moist areas that the striped salamanders claim as their territory since some arthropods will desiccate in dry periods. These arthropods then become the (red-backed) striped salamander's prey while the unstriped salamanders miss this opportunity.
Read also: What do Northern Leopard Frogs Eat?
There are some disputes on which morph has the more diverse diet. In one study, the autumn diet of red-backed morphs was more diverse and of higher quality, and found to be dominated by mites, springtails, and ants, whereas the most important prey for lead-backed morphs were ants, mites, and isopods. A later study notes that this was because the earlier study only compared diets during the fall season, while the later study compared their diets throughout all of the seasons. The later study concludes that the unstriped morph has a broader diet and encounters prey the striped morph does not.
Seasonal Variations in Diet
Spatial distributions of the salamander Plethodon cinereus is observed to be seasonal. In spring, Plethodon cinereus are more likely to exist in groups of around 2 to 7 individuals under some object covers such as rocks and wood, than in the other seasons, while the density on the forest floor stays constant. This is because that spatial dispute starts in spring.
Diet and Environmental Factors
As with all amphibians, the red-backed salamander has permeable skin. They also lack lungs, a condition which is an ancestral trait of the Plethodontidae. Red-backed salamanders are thus entirely reliant on cutaneous respiration for gas exchange. Individuals confine themselves to moist microhabitats (beneath rocks, woody debris, etc. as well as beneath the soil) for long periods of time in order to maintain hydration when surface conditions are inhospitably dry or hot, and are only active on the surface to travel, forage, or reproduce for short periods.
Distribution of P. cinereus are in close contact with the soil on the forest floor. As deciduous forests mature, acid deposition can accelerate the acidification of soils. Acidic conditions can limit the distribution of amphibians and the numbers of sibling species, while the pH value of soil has a strong effect on the density and distribution of P. cinereus. When choosing between acidic and neutral soils, P. cinereus prefers to occupy more neutral soils.
Several other factors, such as moisture and temperature, can affect the population density or dispersion of Botrytis as well. During prolonged dry periods, individuals move down into the soil, while during short dry periods they retreat under logs or rocks. They will avoid very warm areas, and when the temperature drops to 4-5 Celsius degrees, they will retreat to the ground as well. The optimum temperature is 10 to 15 Celsius degrees. Moreover, intraspecific and interspecific competition also affected the distribution of P. cinerea.
Read also: Comprehensive Guide to Weight Loss in NKY
Territorial Behavior and Diet
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 co-defended territories throughout their active periods.
Because of their high population density, red-backed salamanders often maintain small territories that they guard and in which they exclusively forage. Before choosing a mate, females will crush male fecal pellets and investigate the contents, determining if the owner’s territory has ideal prey. Red-backed salamander territories host intricate politics. When a male pairs up, the female will also assume ownership of the area - although she will only guard the territory against other females, and the male only against intrepid males. However, both the male and female are friendlier if the encroaching salamander is a juvenile. Oftentimes, if it has not rained in a while, juveniles risk entering spoken-for territories to forage. Territories appear to be an integral part of the life cycle of red-backed salamanders, but researchers are still trying to figure out just how significant they are. Individuals move only an average of half a meter (1.6 feet) a day. Yet, when displaced by 30 meters (nearly 100 feet), 90 percent returned to their territories, and traveled in a fairly straight path back home almost immediately upon being released.
Threats and Conservation
But while red-backed salamanders are still relatively common, they are facing a number of threats. Logging in the southern Appalachian Mountains has reduced their numbers an estimated 9 percent (representing a loss of around 250 million individuals).
Roads have various negative effects on animal populations. For example, a major source of direct mortality for many species is accidental collisions with moving vehicles. Due to the slow movement of amphibians, it is estimated that the mortality rate of these animals on roads is as high as 10% of the total population each year. Amongst different sizes of roads, it is known that the interstate highway leads to increased genetic differentiation of Plethodon cinereus by microsatellite examination. However, plots on smaller roads were not genetically different compared to that in the case of interstate highways. Narrow paved roads reduce the movement of redback salamanders by approximately 25-75% but do not eliminate the dynamic of the population. So there is little gene flow across very large roads, and the P. cinereus population diverges from each other.
Moreover, salamanders are largely affected by forest management practices thus impacting the food web dynamics and nutrient cycling of the ecosystem they are residing in. In order to conserve the species, proper forest management practice is essential. For instance, even-aged timber harvesting practices are documented which show significantly low abundance and species richness of amphibian creatures in the area.
How You Can Help
- Support the creation of special tunnels called "amphibian migration corridors" (or "salamander tunnels") that allow these creatures to cross safely under roadways.
- Contact your local elected officials and ask them to support local wetland bylaws in your town that afford more protection to vernal pools. In addition, you can support efforts to define and preserve other critical salamander habitat.
- Reduce, reuse and recycle - in that order! Cut back on single-use goods, and find creative ways to reuse products at the end of their life cycle.
tags: #northern #redback #salamander #diet