Northern Zigzag Salamander Plethodon dorsalis

Description: Adult Morphology: Northern zigzag salamanders are small, slender, and often marked with an irregular (i.e. "zigzag") red or orange dorsal stripe. However, many individuals lack this zigzag and are instead a dark brown or gray with lighter frosting. Northern zigzag salamanders often have a noticeable patch of red or orange pigmentation at their armpits, and their ventral coloration is light. Costal grooves number 16-18 (Minton 2001).

Size: Minton (2001) reports body lengths of 35-45.5 mm for males and 34-50 mm for females.

Larvae: Northern zigzag salamanders exhibit direct development, in which the larval stage is bypassed and terrestrial juveniles hatch from eggs laid on land. Juvenile zigzag salamanders appear similar to adults.

Eggs: Observations of zigzag salamander nests are rare, but Mohr (1952) documented twelve adults brooding eggs in a cave in Kentucky. Each nest contained 2-5 eggs, each of which was attached to the rock substrate by a thin filament.

Similar Species:: Northern zigzag salamanders can be easily confused with eastern red-backed salamanders (Plethodon cinereus) and northern ravine salamanders (Plethodon electromorphus). The dorsal stripe on a northern zigzag salamanders is typically jagged, while that of an eastern red-backed salamander is straight-edged. When unmarked by a dorsal stripe, zigzag salamanders are typically lighter in overall coloration than unmarked red-backed salamanders and northern ravine salamanders (which are also much more elongate). Additionally, zigzag salamanders typically have red or orange pigmentation around the insertion of the limbs--a trait that is absent in eastern red-backed salamanders and northern ravine salamanders.

Distribution: Northern zigzag salamanders are distributed from Indiana southward to southern Alabama.

Northern zigzag salamanders are restricted to unglaciated regions of Indiana and are found primarily in the west-central, south-central, and southeastern parts of the state.

Taxonomy: The northern zigzag salamanders (P. dorsalis) is part of a species complex that includes the southern zigzag salamander (P. ventralis) and the Ozark zigzag salamander (P. angusticlavius). Highton (1997) elevated these forms from subspecies to separate species. The northern zigzag salamander belongs to the genus Plethodon and is in the family Plethodontidae which is represented in Indiana by eleven species.

Ecology: Habitat: This species is typically found in hilly, deciduous forest and seems to prefer slightly moister microhabitats than the eastern red-backed salamander. It is not uncommon to discover northern zigzag salamander in shaded ravines and wet, rocky areas. Northern zigzag salamanders are secretive amphibians and are almost always found under rocks, logs, and leaf-litter. Zigzag salamanders are most commonly encountered during the spring and late fall, and they may retreat far underground during the winter and summer.

Diet: The diet of northern zigzag salamanders is composed of a variety of insects and other invertebrates, including spiders, beetles, mites, slugs, and earthworms (Bausmann and Whitaker 1988; Holman 1955; Minton 2001).

Reproduction and Life History: Little is known about the reproductive biology of the northern zigzag salamander, but some evidence (Minton 2001; Sever 1978) suggest that breeding probably occurs in the late fall and spring, with eggs laid in the spring.

Conservation: The largest conservation threats to the northern zigzag salamander are probably related to habitat alteration and destruction from the removal of thick-canopied forest. Minton (2001) reported that the northern zigzag salamander "greatly outnumbered the [red-backed salamander] in the Ohio River counties from Madison to Cannelton" prior to 1970, but that it had declined in relative abundance since. To the best of our knowledge, this trend has not been further examined.

Literature

Bausmann, G. and J. O. Whitaker. 1987. Studies of the habitat and food of sympatric populations of Plethodon cinereus (Green) and Plethodon dorsalis (Cope) in south central Parke County, Indiana. Proc. Indiana Acad. Sci. 97: 513-23.

Conant, R. and J. T . Collins. 1998. Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded. Houghton Mifflin, New York, New York

Highton, R. 1997. Geographic protein variation and speciation in the Plethodon dorsalis complex. Herpetologica 53: 345-356.

Holman, J. Alan, 1955: Fall and winter food of Plethodon dorsalis in Johnson County Indiana. Copeia: 143

Minton, S. A. Jr. 2001. Amphibians and Reptiles of Indiana. Indiana Academy of Science, Indianapolis, IN

Mohr, C. E. 1952. The eggs of the zig-zag salamander, Plethodon cinereus dorsalis. National Speleological Society Bulletin 14: 59-60.

Petranka, J. W. 1998. Salamanders of the United States and Canada. Smithsonian Institute Press, Washington D.C.

Sever, D. M. 1978. Female cloacal anatomy of Plethodon cinereus and Plethodon dorsalis (Amphibia, Urodela, Plethodontidae). Journal of Herpetology 12: 397-406.

Distribution Map
Distribution map of Northern Zigzag Salamander (Plethodon dorsalis)
Photographs