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Eurycea bislineataNorthern Two-lined Salamander

By Elizabeth Vanwormer

Geographic Range

The range of Eurycea bislineata, the Northern two-lined salamander, extends south from southern Quebec and New Brunswick to northern Virginia, and west from New England to northeastern Ohio (Harding 1997).

Habitat

Adult Northern two-lined salamanders prefer woodland or open habitats with sufficient cover provided by layers of fallen leaves, logs, or rocks. Although occasionally found several meters from a water source, adult salamanders commonly occur along stream banks. Adults may remain active in springs, streams, or water laden soil where temperatures are above freezing in winter months. Alternatively, adults may burrow deep into leaf litter, becoming inactive during cold seasons. Larvae typically inhabit the flowing waters of springs or streams (Harding 1997). In at least one region of their range, larvae may also live in lakes (Bahret 1996).

Physical Description

Adult Northern two-lined salamanders, 6.4 to 12.1 cm in length, are characterized by a broad stripe stretching from head to tail along their slender bodies. The stripe, bordered on both sides by narrow black lines that may separate into dashes along caudal regions, ranges in color from yellow to greenish yellow or tan. Medially, the stripe may be marked with a row of dark spots. Yellow or mottled pigmentation extends down the sides, each with fifteen to sixteen costal grooves, and small legs to the yellow belly. Sexual dimorphism exists among males and females, but is more pronounced in the breeding season. During this time period, males possess whitish lower eyelid glands, a distinictive mental gland on the chin, and cirri (protruding extensions of the naso-labial gooves). Young and older Eurycea bislineata larvae differ from adults in coloration and markings. The yellowish ground color of young larvae is spotted with gray or brown on the head and back. Young larvae also possess one dark irregular stripe containing six to nine light spots along upper regions of each side. A secondary row of spots may develop as the larvae age. Distinctive short, reddish brown gills are also characteristic of the larvae (Harding 1997).

Development

Reproduction

Northern two-lined salamanders reach sexual maturity the first fall, or occassionally, one year after metamorphosis. Fertilization occurs internally after the female collects a spermatophore in her cloaca. The breeding season lasts from October through May with females typically laying their eggs in April or May. Females may attach as few as fifteen or greater than one hundred eggs to the underside of firm substrate, usually rock, in flowing streams or spring water (Harding 1997). Recent evidence suggests Northern two-lined salamanders, in some areas of their range, attach eggs to vegetational carpets in fish free, acidic lakes (Bahret 1996). Females tend to guard nests for at least part of the incubation period lasting thirty to sixty days. Only one female typically guards a nest in cases where multiple females deposit eggs at the same site. The larvae measure 1.2 to 1.4 cm snout to vent length (svl) when hatched, and usually transform into semiterrestrial juveniles after two to three years as aquatic larvae. Parental care ceases after eggs hatch (Harding 1997).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)

Behavior

Northern two-lined salamanders exhibit complex courtship behavior. A male uses his head to nudge or poke a potential mate, and encircles the female's head with the front of his body. The male scratches the female's skin with his teeth, possibly allowing secretions from his mental gland to enter the female's bloodstream. It is hypothesized that these secretions may stimulate courtship behavior in the female. The female eventually presses her chin to the male's glandular area at the tail base and the two engage in a "tail straddling" walk. The male then releases a spermatophore which is picked up by the female(Harding 1997).

Adult and larval Northern two-lined salamanders also exhibit antipredation behavior. Garter snakes constitute a significant predatory force on the adults. Different populations and individual adults within a population display unique behavioral patterns to snake contact. Adults touched by the body or head of a snake typically remain immobile. However, if touched by the snake's tongue, adults may demonstrate running or jumping behavior as an alternative to an immobile response. Adults that run after touching a snake tongue also run faster than other adults in the absence of a predator. The chosen response may be correlated with physical ability (Dowdey and Brodie 1989). Adults can also drop their tails (autotomy) which continue to move as the salamander escapes from a snake or other common predators including various mammmals, birds, and larger salamanders (Harding 1997). Larvae also evade predators by altering their behavior. Aquatic larvae utilize chemical cues in the water to detect the presence of predatory fish. If fish are present, larvae seek shelter and may hide for days even after the fish are no longer present. Although they escape predation, larvae may lose access to food resources, threatening their survival. This may indicate an evolutionary trade-off (Petranka et al 1987).

Food Habits

Eurycea bilineata is primarily insectivorous. Adult diets consist of insects such as beetles, mayflies, and springtails, as well as spiders, pillbugs, and centipedes. Adults may also consume other small invertebrates including earthworms and snails. Larvae eat crustaceans and copepods in addition to aquatic larvae of midges, mosquitos, caddisflys, stoneflys,and beetles (Harding 1997). A high dietary overlap exists among the different sizes of larvae which feed continuously throughout the night and day. The larvae act as opportunistic generalists as they mature, continuing to ingest large amounts of small prey after the developmental point when their jaw size can accomodate larger prey items (Petranka 1984).

Economic Importance for Humans: Positive

Northern two-lined salamanders are often collected and used as fish bait by humans (Harding 1997).

Conservation Status

Continued exploitation of Northern two-lined salamanders by humans, for fish bait, or destruction of salamander habitat could lead to reduction or extinction of local populations (Harding 1997).

Other Comments

Prior to 1987, the Eurycea bislineata complex was thought to encompass several subspecies distributed farther south and west of the current accepted range. The subspecies were Eurycea bislineata bislineata, E.b. wilderae, and E.b. cirrigera. In the late 1980's significant genetic divergence was recognized among these groups, and the subspecies were elevated to species status (Jacobs 1987).

Contributors

Elizabeth Vanwormer (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

References

Bahret, R. 1996. Ecology of the lake dwelling Eurycea bislineata in the Shawangunk Mountains, New York. Journal of Herpetology, 30: 399-401.

Dowdey, T., E. Brodie.. 1989. Antipredator strategies of salamanders: individual and geographic variation in responses of Eurycea bislineata to snakes. Animal Behavior, 38: 707-711.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, MI: University of Michigan Press.

Jacobs, J. 1987. A preliminary investigation of geographic genetic variation and systematics of two-lined salamanders, Eurycea bislineata. Herpetologica, 43: 423-446.

Petranka, J., L. Kats, A. Sih.. 1987. Predator-prey interactions among fish and larval amphibians; use of chemical cues to detect predatory fish.. Animal Behavior, 35: 420-425.

Petranka, J. 1984. Ontogeny of diet and feeding behavior of Eurycea bislineata larvae. Journal of Herpetology, 18: 48-55.

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