Notophthalmus viridescens
eastern newt
(Also: red-spotted newt)

The eastern newt, Notophthalmus viridescens, is one of only a few species in the Family Salamandridae native to North America. This newt ranges throughout most of eastern North America, from the Canadian Maritime Provinces west to the Great Lakes and south to Texas, Alabama, Georgia, and Florida (Dunn and Hagen 1999; Petranka 1998; Richmond 1997). There are four recognized subspecies: the red-spotted newt (N. v. viridescens) of the eastern and northeastern U.S. and Canada, the central newt (N. v. louisianensis) of the central states and the deep south, the broken-striped newt (N. v. dorsalis) of the Carolina coastal plains, and the peninsula newt (N. v. piaropicola) of peninsular Florida. (Dunn and Hagen, 1999; Petranka, 1998; Richmond, 1997)

Notophthalmus viridescens inhabits both deciduous and coniferous forests. Immature larvae and the adult newts live in small bodies of freshwater (ponds, small lakes, ditches, and marshes) usually with mud bottoms. Adults can survive on land if their aquatic habitat becomes unsuitable; adults may move onto land during dry periods when the water is low or to rid themselves of ectoparasites. The juvenile "eft" stage lives in lakeshore and woodland habitats and is often seen in forest litter on rainy nights. (Petranka, 1998; Richmond, 1997)

The aquatic larvae have laterally compressed tails, olive colored skin, and feathery gills. The hatchlings range in length from 7 to 9mm and have fairly smooth skin with little toxicity. Although the length of the larval period and the size at metamorphosis varies, they usually transform into a terrestrial "eft" stage after 2 to 5 months. The eft is reddish-orange in color with two rows of black-bordered red spots. It has well-developed lungs, limbs, and eyelids. The eft's skin is dry and somewhat rough and its color is a sign of its toxicity to predators. The eft has a long-slender body with a laterally flattened tail and ranges in length from 3.4 to 4.5 cm. The eft usually transforms into the mature, breeding stage after 2 to 3 years on land. The adult newt varies in color depending on its age and sex, ranging from yellowish-brown to greenish-brown dorsally and have black-bordered red spots. Its ventral color is yellow and black spots speckle the belly. The newt is slightly moist (just enough to keep its skin from drying out), with rough-scaleless skin and indistinct coastal grooves. Its size ranges in length from 7 to 12.4 cm and it has small eyes with a horizontal pupil. During the breeding season, males can be easily identified by their enlarged hind legs, with black-horny structures on the inner surfaces of their thighs and toe tips (used for gripping females during mating), swollen vents, and broadly keeled (high-wavy crest) tails. (Behler, King, and 1979, 1998; Lazell, 1976; Petranka, 1998; Richmond, 1997)

The incubation of the eggs is somewhat dependent on temperature, but generally lasts from 3 to 8 weeks. In early fall, 3 to 4 months later, the aquatic larvae lose their gills, acquire sac-like lungs (heart transforms from two chambered heart to three, capable of supporting lungs), and emerge onto land as an eft. Two to 3 years later, the eft develops a powerful, flattened tail and returns to the water to breed, as an adult, and remains there the rest of its life, if water is permanent. (Lacking permanent water, adult newts will estivate and overwinter on land and enter vernal ponds in spring to breed.) Some eastern newt populations skip the eft stage and immediately transform into breeding adults. There are some coastal populations of eastern newts that become reproductively mature while retaining a gilled "larval" form (i.e., are neotenic). In other populations, newts enter the eft stage but never undergo a complete second metamorphosis, and enter the water only to breed. Both of these latter two cases may be in response to harsher than average environmental conditions. (Behler, King, and 1979, 1998; Lazell, 1976; Petranka, 1998; Richmond, 1997)

Eastern newts have a lifespan of up to 12 to 15 years. However, mortality is high in eggs and larvae. (Petranka, 1998)

With the aid of its flattened tail, Notophthalmus viridescens moves quickly in water, yet is slow on land. Larvae are fairly sedentary, settling at the bottom of the water to hide. They appear to segregate by size in ponds, which probably serves as a defense against larger, cannibalistic adults, however few are lucky enough to survive the first winter. The eft is nocturnal (active during the night) and more active on rainy nights. In dry, sunny weather, the eft will find a cool, moist place to rest and crawl out to feed when damp, darker weather approaches. The adult newt returns to the water and spends the rest of its life there, often foraging both day and night. Winter is spent underground, unless the adults are in permanent water. Newts can often be seen foraging in winter beneath the ice. (Behler, King, and 1979, 1998; Lazell, 1976; Petranka, 1998)

Carnivorous throughout their lives, eastern newts use both chemical and visual cues to locate food. Adults seem to rely more on visual cues when feeding. They don't have a specialized diet, but temperature and water clarity, as well as prey density, can effect the feeding process. (Behler, King, and 1979, 1998; Petranka, 1998)

The aquatic larvae eat small invertebrates including water fleas, snails, and beetle larvae; the terrestrial efts eat small invertebrates, mainly those found in humus and leaf litter, including snails, spring tails, and soil mites; the adult newts eat mainly midge larva and other aquatic immature stages of insects. Adults don't have a specialized diet, eating any small invertebrate that they can find. (Behler, King, and 1979, 1998; Petranka, 1998)

Predators of N. viridescens include birds, mammals, fish, and other amphibians, however many of them are deterred by the newt's toxic skin secretions. (Petranka, 1998)

Eastern newts are important predators of small invertebrates in the freshwater ecosystems of eastern North America. (Petranka, 1998)

Leeches appear to be a major source of adult mortality. Adults will generally flee the water and begin biting or scratching themselves in an attempt to rid their bodies of these ectoparasites, however they're not always successful. (Petranka, 1998)

This species does not have any significant negative economic importance.

The eastern newt may benefit humans by helping to control the populations of aquatic insects, including mosquitoes. They are aesthetically interesting and may play an important ecological role in freshwater and woodland habitats. Eastern Newts are sometimes kept as aquarium or terrarium pets and have even been commercially collected for the pet trade. Effects of this trade on exploited populations is not well documented. (Lazell, 1976)

There is no special status listed for Notophthalmus viridescens. Newts have declined in the face of habitat degradation by humans, but remain locally common in parts of their range. Adult newts will readily colonize man-made bodies of water, even in the presence of predatory fish, as their toxic skin secretions may reduce fish predation. Researchers do believe, however, that eastern newts may be suffering at higher than normal rates from diseases caused by viruses, bacteria, and fungi, due to a variety of environmental problems including pollution. Acid precipitation and deforestation may be other cause of depleted populations. (Dunn and Hagen, 1999)

N. viridescens appears to be involved in a Mullerian mimicry complex, with several other salamander species possibly mimicking the red eft, with its toxic skin secretions.

This newt is capable of locating its home pond through true navigation using its olfaction and light-dependent magnetic compass. (Petranka, 1998)