Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Salamandridae Members:
Notophthalmus viridescens - Eastern Newt

caption

Taxonomy

Class: Amphibia

Order: Caudata

Family: Salamandridae

Subfamily: Pleurodelinae


Taxonomic Comments: The Eastern Newt (Notophthalmus viridescens) is a very wide-ranging species that exhibits geographic variation in size and color patterning. Four subspecies are currently recognized (Mecham 1967). These are 1) the Red-spotted Newt (N. v. viridescens) that is a relatively large subspecies that has well-developed red dorsal spots that are encircled by black, 2) the Central Newt (N. v. louisianensis) that is similar, but usually lacks red spots, 3) the Peninsula Newt (N. v. piaropicola) that is dark olive to black above, lacks red spots, and has a venter that is heavily marked with black spots, and 4) the Broken-striped Newt (N. v. dorsalis) that has broken, red dorsolateral stripes that are bordered with black. The latter three are primarily found in the Coastal Plain and are smaller and more slender than the Red-spotted Newt. The Broken-striped Newt occurs in Coastal Plain habitats from central North Carolina to central South Carolina, while the Peninsula Newt is found in all but the extreme northern portions of Florida. The Central Newt occurs from the Lake Superior region southward to eastern Texas. From there, the range extends eastward through the Gulf Coastal Plain to northern Florida, then north along the Atlantic Coastal Plain to central South Carolina. The Red-spotted Newt occupies the remainder of the range from the Piedmont of Georgia and Alabama northward to southern Canada. Several earlier studies examined genetic variation in this species and found that genetic differences between geographically distant populations were surprisingly low (Petranka 1998). Others since then have examined regional variation using mtDNA or other genetic markers and have found both previously undetected geographic differentiation, as well as patterns of underlying genetic variation that are often discordant with the recognized subspecies (e.g., Gabor and Nice 2004, Lawson and Kilpatrick 2014, Whitmore et al. 2013). The latter could potentially signal significant past or present introgression between forms, or perhaps be explained by other phenomena. Most herpetologists continue to recognize the four subspecies above, but a comprehensive analysis of genetic variation from throughout the range of the species is clearly needed to determine the validity of these recognized taxa.
Species Comments: In addition to the Eastern Newt functioning as a keystone species in many aquatic communities, it has frequently been used in many cellular and developmental studies, particularly those that focus on limb and tissue regeneration. These animals can regenerate their limbs and spinal cords, as well as the lens of the eye. The findings of these studies can hopefully be applied to regenerate structures in humans.

Identification

Description: The Eastern Newt has one of the most variable life cycles of any North American salamander. In addition of the egg stage, most populations have an aquatic larval stage, a terrestrial juvenile stage known as the 'eft' or 'red eft', and an aquatic adult stage. After spending several years on land, the efts migrate back to the breeding sites and transform into aquatic adults. The aquatic adults have lungs and may remain in water for the remainder of their lives. If the ponds dry or stressful environmental conditions develop, they may leave the water and live temporarily on land (Petranka 1998). Adults that leave the breeding sites for prolonged periods undergo further morphological changes and are referred to as 'terrestrial adults'. The morphological changes include a reduction or loss of the dorsal tail fin, and the development of more granular skin.

Gilled adults occur in some populations, particularly in Florida, along the Gulf Coast, along portions of the Atlantic Coast, and in a few scattered locations elsewhere in the range (Takahashi and Parris 2008). They are derived from larvae that undergo partial metamorphosis, but retain the gills and associated structures as sexually mature adults. In other populations the larvae metamorphose, but the terrestrial eft stage is skipped. The transformed juveniles remain in the ponds and eventually mature sexually. Populations with gilled adults and aquatic, lunged juveniles are most common in sandy coastal habitats that lack suitable terrestrial cover for the efts, and have only occasionally been observed in North Carolina.

The more typical aquatic, lunged adult prevails in North Carolina. The ground color of these is light yellow below and olive green to yellowish brown above. The skin is slightly granular and has small black specks and blotches that are scattered over the entire body and generally more pronounced on the tail (Petranka 1998). A series of small red spots with black borders occurs dorsolaterally. Depending on subspecies, these may be separate, or merge to varying degrees to form broken lines down the back. In North Carolina, forms with broken red stripes, or a series of highly elongated dorsolateral spots, are restricted to the southern half of the Coastal Plain (Beane et al. 2010). The lunged adults typically vary from 31-51 mm SVL and 65-112 mm TL, but populations of the Coastal Plain are often smaller. The tail comprises about 50% of the total length and is narrowly keeled above and below except for breeding males. During the mating season the males develop broadly keeled tails, swollen vents, and horny, black ridges and pads on the inner surfaces of the thighs and the tips of the toes. Males also have hedonic pits in a line behind the eye that may be missing or reduced in females, and a yellowish, glandular spot on the posterior margin of the vent that is absent in females.

The gilled adults are uncommon in North Carolina but have been found in a few ponds in sandy coastal areas. They have a yellowish brown or brownish green ground color that is overlain with varying levels of blackish speckling or blotching. Most specimens have a dark stripe through each eye, along with conspicuous reddish gills. Gilled males in breeding condition have swollen cloacae and develop the horny black ridges and pads typical of lunged adults.

The terrestrial adults generally resemble the aquatic adults, but lack keeled tails and have more granular skin. These commonly occur in North Carolina at sites with semipermanent ponds that dry periodically and force the aquatic adults onto land, or in mountainous regions where the adults often overwinter on land. Terrestrial adults that are collected outside of the breeding season are often difficult to distinguish from large, dark colored efts and sometimes overlap in size (Petranka 1998).

The red efts vary from bright vermilion red to dull red or greenish brown and have conspicuously granular, coarse skin. The young efts are typically bright vermilion red, while large specimens that are approaching sexually maturity become duller. The pattern of red and black spotting is generally similar to that of the adults. Efts in our coastal populations are less brightly colored than those in the mountains, while Piedmont populations tend to be intermediate between the two. Aquatic juveniles that skip the eft stage have been found in a few Coastal Plain sites and resemble miniature aquatic adults. They have laterally compressed tails, olive coloration above, and less granular skin than the efts and terrestrial adults.

The hatchlings and older larvae have pond type morphology with bushy reddish to brownish-red gills and broad dorsal fins that extend along most of the back. The ground color is yellowish green above and lighter below. The mature larvae are light brown to yellowish brown above and have slender bodies and blunt snouts. As they grow, they often develop dark flecking and blotching on the body and tail fin. A conspicuous dark stripe occurs from the snout through the eyes. Individuals take on the bright red color of the efts within a few weeks after metamorphosing (Petranka 1998).

Size at sexual maturity varies depending on the life history, geographic race, and geographic locale (Petranka 1998). In general adults of all four subspecies in Coastal Plain populations tend to be smaller on average than those in inland populations. Captured efts of N. v. dorsalis in a North Carolina pond that were transforming into breeding adults averaged 28.4 mm SVL (Harris et al. 1988). In contrast, the smallest aquatic adults of N. v. viridescens that were collected by Chadwick (1944) in the western mountains and Johnson et al. (2017) in the Piedmont of North Carolina were 40 and 37 mm SVL, respectively.

Online Photos: Google iNaturalist

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: Notophthalmus viridescens is found throughout much of the forested regions of the eastern US and adjoining areas of southern Canada, where it occurs from central Ontario eastward to Nova Scotia and Prince Edward Island. The range extends southward to southern Florida and westward to eastern Texas, then northward through eastern Oklahoma to Minnesota. The Red-spotted Newt (N. v. viridescens) is found statewide in North Carolina except for much of the southern half of the Coastal Plain where it is replace by the Broken-striped Newt (N. v. dorsalis). The Red-spotted Newt is very common in the mountains, common in the Piedmont, and uncommon in the northern half of the Coastal Plain. The Broken-striped Newt is most commonly encountered in the Sandhills and in the eastern portion of the Coastal Plain.
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: This very widely distributed salamander inhabits plant communities ranging from northern boreal forests to coastal pine savannas and subtropical forests (Petranka 1998). Most populations have biphasic life cycles, so both suitable aquatic and terrestrial habitats are needed to support local populations. The aquatic adults are found in all sorts of permanent or semipermanent bodies of water including ponds, lakes, canals, flooded ditches, swamps, marshes, sluggish streams, and semi-permanent seasonal wetlands. Sites with abundant emergent or submergent vegetation often abound with newts, and habitats with fish are commonly used since both the larvae and adults are toxic and rarely eaten by fish. Breeding sites that are surrounded by mesic hardwood forests or mixed conifer-hardwood forests provide ideal habitats for the terrestrial juveniles and adults. Populations also occur in southern pine forests where the terrestrial habitats are not too dry. Newts are capable of migrating long distances to and from breeding sites and may use forested habitats many hundreds of meters from the nearest breeding site.

Biotic Relationships: The larvae, juveniles, and adults produce toxic skin secretions and are unpalatable to many predators (e. g., Brodie et al. 1974, Hurlbert 1970a, Kats et al. 1988, Mosher et al. 1964, Petranka 1998, Wakeley et al. 1966). Brodie (1968a) found that the red efts are more than 10 times more toxic than the aquatic adults, and their bright coloration serves as warning coloration to predators. Feeding trials indicate that many species that commonly feed on other salamanders and frogs will avoid newts. Examples include raccoons, garter snakes, numerous species of fishes (however see Lutterschmidt et al. 2015), and predatory birds such as the Red-tailed Hawk. Other predators such as the American Bullfrog, the Painted Turtle, the Common Snapping Turtle, and the Lesser Siren seem to be immune to the toxins (Petranka 1998). Gill (1978a) found that leeches can cause significant mortality to both the larvae and adults and are apparently not affected by skin toxins.

Wrynn et al. (2019) found that larvae of a large dragonfly (Anax junius) that commonly inhabits breeding ponds will readily consume newt larvae and can reduce their survival to metamorphosis. Newts respond to chemical cues from Anax by reducing movements, which likely reduce the risk of being killed. Brossman et al. (2014) found that chemicals from dragonfly larvae can also induce newt larvae to grow wider tails. This likely enhances their swimming ability and reduces predation rates. Other researchers have found that newt larvae can use chemical cues to monitor the presence of predatory Eastern Tiger Salamander larvae (Mathis and Vincent 2000), as well as the presence of adult newts that cannibalize the larvae (Mathis 2003).

The efts and adults will often engage in defensive posturing if attacked or experimentally prodded. If sufficiently provoked, they exhibit an "unken reflex" with the head and tail bent upward, the eyes closed and depressed, and the tail curled (Ducey and Dulkiewicz 1994, Neill 1955, Petranka 1987). This reveals the brightly colored venter that serves as warning coloration. This can be particularly effective for the efts and terrestrial adults of Coastal Plain populations that tend to be rather drab above.

The highly toxic red efts were at one time thought to be part of a Batesian mimicry complex involving several other red-colored salamanders that frequently co-occur with the efts. The efts served as the model, while the Red Salamander (Pseudotriton ruber), Mud Salamander (P. montanus), Spring Salamander (Gyrinophilus porphyriticus), and possibly other species served as the palatable mimics. Subsequent studies reveals that the mimics themselves were unpalatable to varying degrees. As such, all of these species are thought to be part of a Mullerian mimicry complex. Details concerning these studies are in the P. ruber account and summarized by Petranka (1998).

See also Habitat Account for General Forests with Ponds

Life History and Autecology

Breeding and Courtship: The adults breed during the autumn through late spring or early summer, but the specific duration and time of breeding in local populations varies depending on latitude and climate (Petranka 1998). In many northern populations the adults often mate during the autumn and spring. However, females do not lay eggs until the following spring and can store sperm from fall matings in their spermathecae for use in the spring (Bishop 1941a, Sever 2006). Adults at intermediate latitudes such as the mountainous regions of Virginia and North Carolina mostly mate in March-June in association with the spring warm-up (Gill 1978a). Finally, individuals in the southernmost portion of the range, as well as in warmer coastal regions farther north, breed from late-autumn or early winter through spring (Petranka 1998). Mating is usually well underway in coastal South Carolina -- and presumably in coastal North Carolina -- in December and extends at least into late winter (Sever et al. 1996, Taylor et al. 1988).

Courtship behavior has been described by numerous authors and appears to be identical among subspecies (Verrell 1990a). The following is a general overview as summarized by Petranka (1998). The aquatic adults engage in two versions of courtship. One is a very brief form and the second longer and more elaborate. The short version involves instances where a male that is patrolling slowly about a breeding site encounters a female. If a female stays close to a male when he first approaches, the male may perform a brief lateral display, or 'hula', in front of her that involves undulating the body and tail. If the female nudges the male's tail with her snout, then the male will deposit one or more spermatophores. The female then picks these up with her expanded vent and courtship ceases (Humphries 1955, Verrell 1982, 1990a).

If the female is unresponsive to the approaching male, then a more elaborate courtship ensues (Petranka 1998). The male rapidly darts above the female and grasps her just in front of her front limbs with his rear limbs. The pair can remain amplexed like this for several hours, during which time the male alternately rubs the snout of the female with the sides of his head where genial glands are located (Arnold 1977). During this rubbing phase, the male curls his tail forward and rapidly fans it back and forth for a few seconds to direct cloacal secretions towards the female's nostrils. After a prolonged period of rubbing and fanning, the male begins to make violent swimming contortions of his body which causes the female to be dragged and jerked about. The cloaca of the male is strongly everted and pressed against the back of the female during this time. The aggressive jerking activity intensifies over time, at which point the male dismounts. He then moves in front of the female, elevates his tail, everts his cloaca, and undulates his body. The female follows and often presses her head on his tail or cloacal region. The male responds by depositing a spermatophore. If the female again presses against the tail, the male may move forward a few centimeters and deposit one or two additional spermatophores. The female then moves forward and removes the sperm cap from the spermatophore with her cloacal lips. A female frequently will not respond to a male once he releases her and will swim away shortly thereafter. The spermatophore has a broad, disk-shaped base and an abruptly narrowing, spine-like stalk with the sperm mass on top (Bishop 1941a). The entire structure is about 4-7 mm tall. Females court repeatedly during the mating season and most presumably mate with several males.

Males in North Carolina and elsewhere usually outnumber females at breeding sites and compete for the females (Chadwick 1944, Johnson et al. 2017, Petranka 1998). The overrepresentation of males may reflect both higher mortality in females and the fact that females sometimes skip breeding for a year and remain as terrestrial adults on land (Gill 1978a, Grayson et al. 2011). Competition for females often involves males trying to dislodge rival males that are amplexing females. Verrell (1989b) found that males will spend more time trying to dislodge a rival if the female being contested for is large (fecund) or the rival is relatively small.

Rival males may also mimic female behavior during spermatophore deposition by slipping between the male and female and inducing the male to deposit a spermatophore by nudging its tail. At the same time the rival male may deposit a spermatophore and inseminate the female that is nudging his tail. Males sometimes clasp other males and in some instances may continue to court amplexed males as if they were females (Arnold 1972, Massey 1988). When a courting male dismounts, the rival male may mimic female behavior and nudge the male's cloaca. This triggers the courting male to deposit spermatophores and waste gametes.

Massey (1988) made detailed observations of courtship at natural breeding sites in Virginia and New York and found that males successfully inseminated females in only 6% of courtship bouts. In 61% of the unsuccessful courtships, the female deserted the male immediately after it dismounted, while in 35% of courtships the female deserted the male after a rival male slipped in between the pair. In 30 of 48 instances, rival males nudged the cloacae of courting males and induced them to deposit and waste spermatophores.

Reproductive Mode: Females attach their eggs individually to aquatic plants, decaying leaves, or other debris and scatter them widely within ponds or other breeding sites. They often conceal them by wrapping portions of aquatic vegetation around the sticky outer envelopes. The freshly laid eggs average about 1.5 mm in diameter, are light to dark brown above and yellowish green below, and are surrounded by three envelopes. Each female lays a small number of eggs per day and several weeks may be required to lay an entire complement (Petranka 1998). Five females examined by Bishop (1941a) contained 232-376 mature ova, but it is uncertain if females lay all of their mature ova each year.

Females in most populations begin laying their eggs during the spring warm-up. Egg-laying is not strongly synchronized among females within a breeding site and may continue for two or more months after egg laying begins. Egg laying can start in early January in the southernmost populations, but generally does not begin until mid-March or later farther north (Petranka 1998). Harris et al. (1988) first found hatchings in a pond in the Sandhills of North Carolina in late April and reported that females oviposit from April-June. Females in the southern Appalachians and in northern populations begin laying in late March through mid-April and continue until May, June, or early July depending on the location (Bishop 1941a, Chadwick 1944, Gill 1978a, Pope 1924). The eggs require about 20-35 days to hatch depending on water temperatures (Petranka 1998).

Aquatic Life History: The larvae are gape-limited, euryphagous predators that feed on small invertebrates (Petranka 1998). They tend to be secretive during the day and more active after dark where they either enter the water column to feed, or prowl slowly over aquatic vegetation or leaf litter in search of prey. The larvae use both chemical and visual cues to locate food (Pope 1924). The hatchlings and smaller larvae feed on very small prey such as ostracods, copepods, cladocerans and small midges. Older larvae continue to take small invertebrates, but also incorporate larger prey into the diet as their gape widens. Ostracods, copepods, chironomid larvae, snails, and finger clams were the most important prey in New York specimens that were examined by Hamilton (1940), while cladocerans, ostracods, amphipods, chironomids, odonates, clams, and snails were eaten by larvae in New Hampshire (Burton 1977). Larvae at a coastal South Carolina site fed mostly on cladocerans and consumed larger prey such as chironomid larvae as they grew (Taylor et al. 1988). A variety of other prey have been documented in the diet, including aphids, beetle larvae, mosquitoes, water mites, protozoans and turbellarians (Petranka 1998).

In populations with a typical life cycle that includes the larval and eft stages, the larval stage is relatively brief and lasts only 2-5 months (Petranka 1998). Metamorphosis typically occurs during the summer months through early autumn (Petranka 1998). Reported times for metamorphosis include in July and August in Massachusetts (Noble 1929b, Smith 1920), in September in Illinois (Brophy 1980), from mid-August through November in western Virginia (Gill 1978a) and from July through early November in New York (Bishop 1941a, Hurlbert 1970b). In North Carolina, transforming larvae have been observed in August and September in both the mountains (Chadwick 1950) and Coastal Plain (Harris et al. 1988). In populations where gilled adults and aquatic juveniles occur, length of the larval period is highly variable depending on whether individuals metamorphose into aquatic juveniles or remain in ponds and mature sexually (Noble 1929b, Petranka 1998).

The average size at metamorphosis for N. v. viridescens is typically 19-21 mm SVL and 35-38 mm TL and is remarkably similar for several populations that have been studied from throughout the range (e.g., Brophy 1980, Healy 1973, 1974a, Worthington 1968). Average size at metamorphosis in a mountain population in North Carolina was 21 mm SVL and 38 mm TL (Chadwick 1950). The larval period in a Sand Hills population in North Carolina that was studied by Harris et al. (1988) lasted 4-5 months, although a few larvae overwintered. The average size at metamorphosis was 33 and 50 mm TL during two consecutive years, with pond drying triggering early metamorphosis at a small size in one year. Growth appeared to be density-dependent and averaged only 5 mm TL/month when larval densities were high versus 11 mm/month when larval densities were low.

Although the larvae are toxic and unpalatable to many predators, larval survivorship to metamorphosis is normally very low. Typically < 2-3% of the hatchlings surviving to metamorphosis (Petranka 1998). In some populations, it is not uncommon for any metamorphs to emerge from the breeding ponds in a given year (Gill 1978a, Massey 1990).

The Coastal Plain subspecies have more variable life histories relative to the Red-spotted Newt. Examples of gilled adults and aquatic juveniles are commonplace relative to the more stereotypic life cycle of the Red-spotted Newt. A fundamental question is whether these differences reflect differences in life history plasticity or not. Harris (1987) found that larvae of N. v. dorsalis from the Sandhills of North Carolina were far more likely to become gilled adults or aquatic juveniles when experimental densities in artificial ponds were low and food levels were correspondingly high. Takahashi and Parris (2008) also experimentally tested whether the observed subspecific differences in life-cycle polyphenism was genetically based or environmentally induced by raising larvae under three different hydrologic regimes (short-drying, long-drying, and permanent water conditions). They found that N. v. viridescens metamorphosed to efts regardless of hydrologic conditions. In contrast, two Coastal Plain subspecies (N. v. dorsalis and N. v. louisianensis) exhibited greater plasticity and produced either efts under short-drying conditions, or aquatic juveniles and gilled adults under longer hydroperiod regimes. Takahashi et al. (2011) conducted a companion study across the contact zone of N. v. viridescens and N. v. dorsalis in South Carolina and found parallel results. The differences in plasticity of life history traits between subspecies correlate with the availability of natural wetlands and abundance of mesic terrestrial habitats in the two regions. These studies suggest that the complex life-history variation seen in N. viridescens is often plastic and reflects adaptations to local and regional environmental conditions.

The aquatic adults are diurnally active and can often be seen moving slowly about pond bottoms, exploring beds of macrophytes, or swimming in the water column in search of prey. They feed on both zooplankton as well as larger aquatic organisms. Some of the known prey include oligochaetes, leeches, amphipods, sphaeriid clams, cladocerans, and a variety of aquatic insects such as hemipterans, beetles, mayflies, stoneflies, lepidopterans, dipterans, and odonates (Petranka 1998). Bishop (1941a) noted that the adults in New York sometimes take small fishes such as sticklebacks. Start and DeLisle (2018) reported that males tend to forage in the water column on pelagic prey such as zooplankton, while females more often forage on pond bottoms on benthic prey such as insect larvae and ostracods. They demonstrated that the sex ratios in breeding sites can strongly influence the composition of invertebrate communities in experimental ponds. The annual survival of the aquatic, lunged adults is often low. Gill (1978a) estimated that females on average breed only 1.3 times during their lifetimes versus 1.9 times for males. It is uncertain to what extent they incur mortality during their stay on land versus in the breeding sites.

The adults often are major predators on the eggs or larvae of frogs and ambystomatid salamanders (Bishop 1941a, Gill 1978a, Hamilton 1932, Walters 1975, Wood and Goodwin 1954), and often play important roles in structuring amphibian communities in North Carolina (Fauth 1990, Morin 1983a, Wilbur and Fauth 1990). The adults also frequently cannibalize the larvae (Burton 1977, Morgan and Grierson 1932), which may play a role in regulating local population size.

Terrestrial Life History: In populations with typical life cycles, the efts disperse away from ponds shortly after metamorphosis and move into surrounding forests. They often move long distances from the breeding sites before establishing home ranges in forested settings. Healy (1974a, 1975) conducted detailed studies of the life history of the efts in Massachusetts and found that they take about 1 year to migrate to woodlands 800 m from their natal pond. They moved beneath leaf litter during dry weather and were most active on the ground surface during rainy weather. The average home range was about 270 m2, and they often shifted to different microhabitats seasonally to exploit shifts in local food patches.

The efts require greater time to reach sexual maturity than do individuals that skip the eft stage and transform directly into aquatic juveniles or gilled adults (Petranka 1998). Bishop (1941a) reported the eft stage to last 2-3 years in New York populations, while Chadwick (1944) estimated it to last 4 years in mountain populations in western North Carolina. These are based on size distributions in populations and may be conservative because age classes are often difficult to distinguish in older age groups. The eft stage was reported to lasts 4-7 years in a Maryland population based on skeletochronological aging, which is much more reliable (Forester and Lykens 1991). In a North Carolina Coastal Plain population, maturing efts are only slightly larger than metamorphosing larvae. This suggests that some individuals may reproduce when only 1-year old (Harris et al. 1988). In northern populations the eft stage is estimated to lasts 4-5 years -- but in some cases as long as 7 years -- and most individuals do not become sexually mature until 5-6 years old.

As they near sexual maturity, the efts begin migrating back to breeding habitats where they transform into aquatic adults. Individuals typically reach sexual maturity shortly before or immediately after reaching the breeding sites. Depending on the population, movements to the ponds may occur in the autumn, in the spring, or during both times of the year (Petranka 1998). Individuals typically move during rainy weather and both during the day and at night. In western North Carolina efts emigrated back to a breeding pond during the autumn (Chadwick 1944), but in mountainous regions of Virginia the efts returned to the ponds mostly during the spring (Gill 1978a). In a Massachusetts population, large efts begin moving towards the breeding ponds in July and first arrived at the ponds in August (Healy 1975).

Healy (1973, 1974a) compared coastal populations with aquatic juveniles to an inland population with efts and found that the aquatic juveniles reach sexual maturity in about 2 years versus 5-6 years for efts. In artificial pond experiments, the gilled adults may reach sexual maturity in as little as 7 months post-hatching (Harris 1987). The advantage of the eft stage is that it is a dispersal stage that allows the offspring of adults to colonized new habitats. Because the adults show very strong fidelity to home ponds (Gill 1978a), and the efts show far less fidelity (Hurlbert 1969, Gill 1978a), the eft stage is the primary dispersal stage in the life cycle (Petranka 1998). Gill (1978a) showed that movements of efts between local ponds in Virginia was essential for maintaining the larger metapopulation.

In addition to the use of forests by the efts, the aquatic adults often leave ponds in late summer or autumn and transform into terrestrial adults. In many populations where the ponds freeze during the winter, some or all of the adults overwinter on land, then faithfully return to their home ponds the following spring to breed (Gill 1978a, Gill 1979, Hurlbert 1969, Massey 1990). Regosin et al. (2005) found that most adults that left a pond in Massachusetts overwintered within 100 m of the pond. Newts use olfaction and a light-dependent magnetic compass to locate home ponds, and will return to their home ponds if experimentally displaced to nearby ponds (Petranka 1998). Most adult N. v. dorsalis in a North Carolina pond that were studied by Harris et al. (1988) also abandoned the pond during the summer and return in the fall and winter to breed. Rather than leave the ponds, the adults of N. v. dorsalis and N. v. louisianensis may simply hide in moist mud or beneath plant debris when seasonal ponds dry (Fauth and Resetarits 1991, Liner 1954, Morin 1983a).

Grayson et al. (2011) studied two populations in Virginia where only a portion of the aquatic adults migrated on to land and found that newts can switch migratory tactics over their lifetime. Males were more likely to stay in ponds, and females were more likely to stay on land and skip breeding between years. Individuals that remained in ponds tended to have higher fitness than those that migrated, but sometimes suffered significant mortality from winterkill in frozen ponds. Density-dependent processes in the ponds also appear to strongly influence the probability of individuals migrating and becoming terrestrial adults (Grayson and Wilbur 2009).

The terrestrial stages appear to be opportunistic generalists that take a wide variety of invertebrate prey. The red efts are often active on the surface following summer rains. They frequently feed in the leaf litter on tiny invertebrates such as collembolans and occasionally climb low vegetation in search of food. They sometimes aggregate near rotting mushrooms or other food patches where invertebrates are concentrated (Petranka 1998). The terrestrial adults have similar diets, but show a weak tendency to take larger prey. MacNamara (1977) conducted a detailed study of juveniles and adults at a site in New York. Tiny prey such as springtails and mites comprised most of the prey, with some individuals having more than 2,000 springtails in their stomach. Numerous other prey were taken, including species from 25 orders and 58 families of invertebrates.

General Ecology

Population Ecology: Local populations of the Eastern Newt are often organized as metapopulations. A metapopulation is a regional group of local populations that are connected by the movement of individuals between populations. Connectivity between local populations allows for the recolonization of ponds following local extinctions, and reduces the chance of a local population going extinct when a population is in decline. Gill (1978a, b) conducted detailed studies of a cluster of ponds in the mountains of western Virginia that were organized as a metapopulation. The aquatic adults never moved between ponds, but the mature efts migrated to ponds other than their natal pond. Many ponds produce few if any metamorphs year after year and the production of juveniles was not sufficient to maintain populations of breeding adults in most ponds. Nonetheless, these ponds supported healthy populations of adults --presumably due to the annual recruitment of maturing efts from productive ponds within the metapopulation. Gill (1978a, b) concluded that the existence of breeding populations in most ponds was completely dependent on metapopulation structure and annual immigration from productive ponds.

Community Ecology: The Eastern Newt plays important roles in structuring both invertebrate and vertebrate communities in aquatic sites. The adults are important predators on both the eggs and larvae of other amphibians that share breeding sites. Several researchers have examined interactions between newts and other vertebrates in artificial pond experiments (Petranka 1998). They often function as keystone predators and can mediate competition between anuran tadpoles by differentially preying on community members (e. g., Alford 1989, Morin 1981, 1983b, Wilbur et al. 1983). They can also affect the abundances of zooplankton species (Morin et al. 1983). Many of these interactions are density-dependent. Fauth and Resetarits (1991), for example, examined interactions between lesser sirens, newts, and anuran tadpoles in artificial ponds and found that the effect of sirens on newts depends on newt densities. At low newt densities sirens reduce the reproductive success of newts by preying on their larvae, but at high newt densities they enhance reproductive success by reducing the survival of adult newts that prey upon and compete with newt larvae.

Adverse Environmental Impacts

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Environmental Threats: Perhaps the greatest treat to this species is Batrachochytrium salamandrivorans, which is an emerging, invasive chytrid fungus that is currently spreading across Europe and causing mass mortality events of several salamandrid species. This pathogen has not been detected in North America as of 2021, but it could very easily be introduced and impact many native salamanders. The Eastern Newt appears to be particularly vulnerable, and B. salamandrivorans could potentially drive many populations extinct (Tompros et al. 2021).

Status Comments: The Eastern Newt is common throughout much of eastern North America, including North Carolina. Because it can tolerate fish, many populations have become established in constructed ponds and reservoirs and are flourishing in many areas of North Carolina. Populations also appear to have increased in many areas since beavers have recovered after being nearly extirpated from North Carolina during the last two centuries (Petranka 1998).

Stewardship: Local populations are best maintained by having clusters of local ponds with metapopulation structure. Mesic, forested habitats are essential for the terrestrial stages. Since the efts move long distances from the breeding sites, forest buffers that extend several hundred meters from the breeding sites are recommended for maintaining healthy adult populations.

Photo Gallery for Notophthalmus viridescens - Eastern Newt		11 photos are shown.
	Recorded by: tom ward Buncombe Co. Comment: An eft perched on a Christmas Fern at night.	Recorded by: tom ward Buncombe Co.
	Recorded by: tom ward Buncombe Co.	Recorded by: jude urfer Buncombe Co. Comment: A metamorph; note the gills that have not been fully resorbed.
	Recorded by: jude urfer Buncombe Co.	Recorded by: Jim Petranka Buncombe Co. Comment: A pair of red efts.
	Recorded by: Owen McConnell Graham Co.	Recorded by: Doris Ratchford Ashe Co.
	Recorded by: Jim Petranka Buncombe Co. Comment: Defensive posturing by a terrestrial adult.	Recorded by: Owen McConnell Graham Co.
	Recorded by: Jim Petranka Buncombe Co. Comment: A courting pair of adults.

Notophthalmus viridescens - Eastern Newt

Photo Gallery for Notophthalmus viridescens - Eastern Newt

11 photos are shown.