Amphibians
Two-lined Salamander
Eurycea bislineata · also called northern two-lined salamander
Turn over a flat stone at the edge of almost any clean brook in the north-eastern United States and there is a fair chance a small, quick, yellow salamander will squirm out and vanish into the gravel. The two-lined salamander is one of the most common amphibians of eastern streams, and one of the easiest to recognise once you know the two dark lines to look for.
Overview
Eurycea bislineata is a slender lungless salamander, usually 6 to 12 cm long including a tail that makes up more than half the length. The back is yellow to tan or greenish with fine dark flecks, bordered by a dark stripe down each side; the belly is plain yellow. It lives along streams, seeps, and springs and in wet floodplain forest across north-eastern North America, and it breathes entirely through its skin and mouth lining.
A slow start in the stream
Females lay a cluster of eggs on the underside of a submerged stone and often stay to guard them. The gilled larvae then spend one to three years on the streambed before transforming into terrestrial adults. Adults hunt small invertebrates at night, moving out onto wet ground when it rains and retreating underground in dry weather. Caught by a predator, the salamander can shed part of its tail and regrow it slowly.
Breeding males transform
In autumn and winter, mature males change shape: they grow enlarged jaw muscles, long teeth that can nick a female’s skin to pass on courtship secretions, and small projections called cirri beneath the nostrils. The northern two-lined salamander is one of several nearly identical species — southern, three-lined, and Blue Ridge — that divide up eastern North America between them.
Status
The two-lined salamander is Least Concern and often abundant. Its weak point is its need for clean, cool, well-oxygenated water and shaded banks, so it disappears from streams damaged by sediment, warming, and pollution, which is why biologists track it as an indicator of stream health.
Two-lined Salamander: common questions
How do you tell a two-lined salamander from other brook salamanders?
Look for the pair of dark stripes. A two-lined salamander has a fairly bright yellow to tan back with a clean dark line running along each side, from the eye back onto the tail, and a plain yellow belly. It is slender, usually 6 to 12 cm long including the long tail, with 14 to 16 grooves along the flanks. The similar northern dusky salamander is bulkier, drabber, has a pale line from eye to jaw, and holds its tail more knife-edged. The red salamander and mud salamander are stouter and reddish with dark spots rather than stripes.
Where does the two-lined salamander live?
In and beside cool running water. Adults are found under stones, logs, and leaf packs at the margins of small streams, brooks, springs, and seepages, and in wet floodplain woods, roadside ditches, and spring-fed wetlands. They rarely stray far from moisture. On rainy or humid nights they move out onto the wet forest floor and streambanks to hunt, and in dry spells they retreat underground or deep into the streambed. The larvae are fully aquatic and live on the bottom of the stream among gravel and dead leaves.
Is the two-lined salamander dangerous or venomous?
No. It has no venom and no way to harm a person. Like many salamanders its skin produces mild distasteful secretions that deter some predators and can irritate if rubbed into the eyes or a cut, so it is good practice to wet your hands before handling one and wash afterward, mostly for the animal's protection since dry or lotioned hands damage its skin. It does not bite in any meaningful way. The elongated teeth that breeding males grow are for courtship, pressed against a female's skin, not for defence.
Why are two-lined salamanders important to streams?
They are abundant mid-level predators in headwater streams, eating vast numbers of small invertebrates and in turn feeding fish, snakes, birds, and shrews, so they move a lot of energy through the system. Because they need clean, cool, well-oxygenated water and an intact streamside canopy, and because they are easy to find and count, biologists use them along with dusky and spring salamanders as indicators of stream health. A stream that has lost its two-lined salamanders has usually also lost water quality to sediment, warming, or pollution.