Southern Red-backed Salamander
Plethodon serratus Grobman
Plethodon serratus is small, dark, and slender with short legs and a distinctive red or red-orange stripe running from the base of its neck to its tail. The stripe runs down the middle of its back (hence the name); it sometimes has straight edges, sometimes saw-toothed edges that correspond with its costal grooves (Figure 1). The sides are brownish-gray with some red pigment, and the belly is covered with gray-blue mottling. Typical adult male red-backed salamanders range from 81 to 105 mm on average, with the largest recorded specimen in Missouri measuring 107 mm (Johnson, 2000).
The southern red-backed salamander is often confused with the Ozark zigzag salamander, but there are a number of distinguishing characteristics to tell the two apart. The dorsal stripe on the two species differs: the Ozark zigzag salamander (P. angusticlavius) has a stripe that is usually very thin (less than 1/3 the body width) and is sometimes broken into lobes, whereas the stripe on the southern red-backed salamander is generally uniform in width and has serrated edges. Furthermore, the belly of has gray mottling, while the Ozark zigzag has black and white mottling on its stomach (Johnson, 2000).
The diet generally consists of small invertebrates, mainly ants and beetles but also snails, spiders, millipedes and centipedes (Edwards, 2008).
There have been no formal studies on predation of this species, but the most likely predators include small snakes, birds, shrews and small mammals such as skunks, and possibly even larger salamander species (Edwards, 2008).
Male salamanders compete for mates, and tend to defend their territories more aggressively against other males than against females, especially during the breeding season. The breeding season generally occurs during the late fall and winter, and females lay their eggs (between 4 and 10) in underground cavities (under rotten logs, rocks, etc) during June and July. The eggs are attached to a thin stalk suspended from the top of the cavity and are around 4.5 mm. Females remain with the eggs until they hatch between August and October. The hatchlings are small replicas of adults and average 20 mm in length. Juveniles reach full maturity within 2 or 3 years of hatching (Edwards, 2008).
There are no published studies on the lifespan of southern red-backed salamanders, but other salamanders in this genus have been known to live up to 25 years (Edwards, 2008).
Southern red-backed salamanders tend to live in forests where they can be found under rocks, rotten logs and clumps of moss. During the dry season they are often found near seeps and springs.They can be found under moist leaf litter in the spring (April to early June), rocks and logs from September to March, while in the summer months (June through August), they burrow underground to stay cool and moist (Edwards, 2008).
Within Missouri, most populations exist in southern, central, eastern and southeastern Ozarks (Figure 3). Outside of Missouri, there are isolated populations in eastern Tennessee, the southwestern corner of North Carolina, northwestern Georgia, eastern Alabama, central Louisiana, west-central Arkansas and eastern Oklahoma (Edwards, 2008).
Jaeger et al (2005) studied the ability of southern red-backed salamanders to detect intruders to their territory, particularly through their ability to detect volatile pheromones. The amount of time the individual spent in all-trunk raised threat postures and the number of times their nose touched the pheromone-laden filter paper placed inside their habitat was recorded. The research concluded that these salamanders are able to detect intruders without having to roam their territory; instead, they can detect volatile components of an intruder’s pheromones left on the substratum (Jaeger, Martin and Prosen, 2005). This research is important in understanding how southern red-backed salamanders interact within its environment and how their behavior affects other species in their immediate environment. In particular, these male salamanders are able to distinguish between male and female pheromones and respond more aggressively to male presence. With this ability, the males are able to detect and respond to potential threats much quicker than if they have to roam their territory.
Deckard et al (1998) investigated aggression and territoriality in southern red-backed salamanders. They tested the hypothesis that P. serratus are more aggressive and less submissive as residents (that is, when they are within their own territory) than they are as intruders (within other’s territory); they determined this by recording specific behaviors considered “aggressive” (such as biting, looking at the other salamander and moving towards it) and “submissive” (such as keeping towards the edge of the enclosure and moving away from the other salamander). The second experiment compared responses of salamanders to self vs. non-self specific scent marks by recording the number of times each individual pressed its nose against the substrate. The research concluded that specimens of these salamanders tend to act more aggressively in defending their own territory than when they were in another individual’s territory, and that they can differentiate between self and non-self specific scents (Deckard, Duer and Mathis, 1998). This study is important because it helps us understand how P. serratus interacts with its environment; also, such behaviors as aggression and territoriality can have affects on an individual’s access to food, shelter and mates. Furthermore, in responding aggressively, they are able to exclude intruders from their territory.
Notes: In Missouri, the southern red-backed salamander was identified as Plethodon cinereus (eastern red-backed salamander) until the mid 1970’s, at which point researchers showed that the Missouri populations were actually related to the Arkansas populations of southern red-backed salamanders, as well as populations in other southeastern states. The Missouri populations were then reclassified as the southern red-backed salamander (Johnson, 2000).
Pictures and Photographs:
Conant R, Collins J.T. Reptiles and Amphibians Eastern/Central North America. Peterson Field Guides. Published 1998.
Deckard K, Duer C, Mathis A. Laboratory Evidence for Territorial Behavior by the Southern Red-Backed Salamander, Plethodon serratus: Influence of Residency Status and Pheromonal Advertisement. The Southwestern Naturalist. 1998:43(1):1-5. http://jstor.org/stable/30055325. Accessed November 25, 2013.
Edwards, B. Plethodon serratus: Southern Red-backed Salamander. Animal Diversity website. http://animaldiversity.ummz.umich.edu/accounts/Plethodon_serratus/#caac09f5e4fb38b550e4ff4d0245737. Published 2008. Accessed November 25, 2013.
Jaeger RG, Martin SB, Prosen ED. Territorial Red-Backed Salamanders Can Detect Volatile Pheromones from Intruders. Herpetologica. 2005:61(1);29-35 http://www.jstor.org/stable/3893557. Accessed November 25, 2013.
Johnson, T. R. Southern Red-backed Salamander. In: ed. The Amphibians and Reptiles of Missouri. Jefferson City, MO: Missouri Department of Conservation; 2000: 87-88.