© 2010 Stephen Bennett (1 of 43)
Country distribution from AmphibiaWeb's database: United States
Can you confirm these amateur observations of Eurycea guttolineata?
Eurycea guttolineata (Holbrook, 1838)
Travis J. Ryan1
1. Historical versus Current Distribution. Three-lined salamanders (Eurycea guttolineata) are distributed throughout much of the southeastern United States. From west to east, the range of three-lined salamanders begins along the eastern bank of the Mississippi from Louisiana, north through all of Mississippi and Tennessee and into Kentucky. Eastward, they are distributed throughout Mississippi (save for the northeastern corner) and Alabama (save for the northern portion), all but the northwestern and southeastern extremes of Georgia, all of South Carolina, most of western and central North Carolina, and eastern Virginia. The absence of the three-lined salamanders from the bulk of North Carolina’s Coastal Plain is particularly curious. Populations rarely are found above 800 m and almost always below 1,000 m (Fisher, 1887; Ireland, 1979; Freeman and Bruce, 2000).
There is no evidence to support a difference between the current and historical distributions, but Petranka (1998) points out that the loss of bottomland hardwood forests throughout the Southeast has undoubtedly resulted in the extirpation of many populations. However, links between habitat loss and any putative population declines have not been empirically demonstrated.
2. Historical versus Current Abundance. Three-lined salamanders are fairly abundant throughout their range. While there have been a fair number of population studies of its sister species, E. longicauda (long-tailed salamanders), the population ecology of three-lined salamanders has not been studied nearly as well. Anecdotally, some of the populations first studied two and three decades ago (Bruce, 1970, 1982) apparently are still stable.
3. Life History Features.
A. Breeding. Courtship has not been described for three-lined salamanders, and relatively little is known of their reproductive activities.
i. Breeding migrations. Three-lined salamanders rarely stray far from aquatic habitats, but are found more frequently at the terrestrial/aquatic interface and in the water during the late fall, winter, and early spring. If there is a migration per se from terrestrial sites to aquatic ones, it occurs in the fall, probably coincident with the onset of the breeding season. Marshall (1999) suggested an extended breeding season (July–December).
ii. Breeding habitat. Breeding occurs in lentic and slow-moving lotic systems, such as sluggish streams and seeps, bogs, and cypress bays (Petranka, 1998).
B. Eggs. Oviposition occurs in the winter, but varies considerably in published reports and is likely a consequence of both spatial (geographic) and temporal (year-to-year) variation. Gordon (1953) reports December oviposition. In North Carolina–South Carolina populations, a February oviposition date seems more likely, based on the appearance of hatchlings (Bruce, 1970, 1982; Freeman and Bruce, 2000). Marshall (1999) suggested that oviposition could occur as early as November in some populations.
i. Egg deposition sites. Few egg clutches have been observed. Mature ova are 2.5–3.0 mm in diameter. Bruce (1970) found hatchlings and advanced embryos scattered on the bottom of a cistern in mid March. The eggs were not attached to any cover object, which is unusual for eastern Eurycea. Given the unconventional location of the embryos and the fact that no female was in attendance, Bruce (1970) speculated that eggs had washed into the cistern rather than having been oviposited there.
ii. Clutch size. Mount (1975) found groups of 8–14 eggs associated with several adults in a covered concrete reservoir associated with a shallow spring. Beyond this, we are aware of no reliable data regarding fecundity (Ryan and Bruce, 2000).
C. Larvae/Metamorphosis. The larval life history of the three-lined salamander is one of the best studied aspects of the species with at least five comprehensive studies.
i. Length of larval stage. In North Carolina, hatchlings emerge at 10–13 mm and undergo metamorphosis when they are 22–27 mm SVL after a 4–6 mo larval period (Bruce, 1970, 1982). Larvae in montane populations occasionally will overwinter and transform during the early summer, 16 mo after hatching and at between 30 and 32 mm SVL. The effect of elevation on larval periods was studied in a more comprehensive manner by Freeman and Bruce (2000). They investigated changes in timing of and size at metamorphosis over an elevational gradient within a single watershed. At the low elevation populations (in Georgia and South Carolina), metamorphosis came 5–6 mo post hatching. Larvae overwintered and delayed metamorphosis until 14–15 mo post hatching in the high elevation populations in North Carolina. There were no differences between size at hatching or growth rate between the high and low elevation populations. Freeman and Bruce (2000) posited that differences in hydrological stability (which is greater in the high elevation populations) likely accounts for these differences. Marshall (1999) also found metamorphosis occurring at 5–6 mo post hatching. However, his analysis of variation in size and age at metamorphosis led him to conclude that three-lined salamander larvae are adapted to warm, stable aquatic environments and found no support for their adaptation to variable habitats.
ii. Larval requirements. Larvae are found in the same slow-moving streams, bogs, and marshes as the adults.
a. Food. Larval three-lined salamanders most likely feed on small invertebrates (Petranka, 1998), but there are no detailed studies of foraging behavior or gut content analyses.
b. Cover. It is difficult to quantify or even accurately describe the cover object of three-lined salamander larvae, as they most frequently inhabit waters that make direct observation extremely difficult. Larvae are captured most easily by thrusting a dipnet (e.g., Freeman and Bruce, 2000) rather blindly through the shallow water near the land–water interface or in deeper waters along the substrate. Larvae most likely seek refuge in decaying vegetation along the stream/pond/bog/marsh bottom (Bruce, 1982).
iii. Larval polymorphisms. Unknown.
iv. Features of metamorphosis. Metamorphosis occurs fairly early in three-lined salamanders (see "Length of larval stage" above). The first sign of metamorphosis is the adoption of an adult pigment pattern that frequently far precedes other signs of metamorphosis (such as the resorption of the tail fin and external gills; Bruce, 1970).
v. Neoteny. Paedomorphosis is not known in three-lined salamanders.
vi. Post-metamorphic migrations. Recently metamorphosed three-lined salamander juveniles are encountered most frequently at the land–water interface, but it is not altogether unlikely to find juveniles in the surrounding forest among adults. Coordinated migrations (in the manner of various Ambystoma, which may frequently be members of the same guild) per se are unknown and unlikely.
D. Juvenile Habitat. Same as adult habitat, see below.
E. Adult Habitat. Mainly terrestrial as adults, however, they rarely are found considerable distances from wetlands. Most abundant in river-bottom wetlands and in the vicinity of springs and streams (sometimes ditches, vernal ponds, and bogs) where seepage keeps the ground moist. Animals occasionally are found some distance from water, but are good swimmers and at home in the water. Like most other plethodontids, three-lined salamanders are primarily nocturnal, but may be found during the day under cover objects. Surface activity is closely tied with surface moisture; adults are likely to be encountered foraging on humid or rainy nights shortly after sunset (Petranka, 1998).
F. Home Range Size. Unknown. Because three-lined salamander adults do not defend territories (see below); the definition of individual home ranges is problematic. Furthermore, detailed autecology studies have not been published to date.
G. Territories. According to Jaeger (1988), three-lined salamanders are one of the few plethodontid salamanders that are not territorial.
H. Aestivation/Avoiding Dessication. Aestivation is unknown and unlikely.
I. Seasonal Migrations. Seasonal habitat shifts in response to temperature (toward the water in fall and winter as temperatures descend and away from aquatic habitats in the spring when air, ground, and water temperatures rise) occur, but highly synchronized movements have not been described.
J. Torpor (Hibernation). Unknown and unlikely.
K. Interspecific Associations/Exclusions. Three-lined salamanders often are associated with southern two-lined salamanders (E. cirrigera) or Blue Ridge two-lined salamanders (E. wilderae). Little is known about how (Petranka, 1998) or whether these species compete. Bruce (1982) found three-lined salamanders and Blue Ridge two-lined salamanders inhabiting the same creeks in western North Carolina with no noticeable adverse effects on either; e.g., both species demonstrated life history patterns consistent with isolated populations (Bruce, 1970, 1988). The differences in larval life history (see Ryan and Bruce, 2000) may be sufficient to reduce competition prior to metamorphosis. As adults, three-lined salamanders tend to stay closer to aquatic habitats than do Blue Ridge two-lined salamanders or southern two-lined salamanders, particularly in the summer (T.J.R., personal observations); this may reduce competition in the post-metamorphic phase. At the higher elevation extreme, other stream-dwelling plethodontids may be encountered, such as Ocoee salamanders (Desmognathus ocoee) and more rarely seal salamanders (D. monticola), red salamanders (Pseudotriton ruber) and mud salamanders (P. montanus; Freeman and Bruce, 2000). However, because three-lined salamanders also inhabit more lentic waters, they also may be syntopic with members of the local pond-dwelling guilds (e.g., eastern newts [Notophthalmus viridescens] and spotted salamanders [Ambystoma maculatum]; Freeman and Bruce, 2000). Competitive interactions among these species, in either lentic or lotic environments, have not been evaluated.
Until relatively recently, three-lined salamanders were considered a subspecies of long-tailed salamanders (E. longicauda), with which they were believed to hybridize (Bailey, 1937; Martof and Humphries, 1955; Valentine, 1962; Ireland, 1979). Carlin (1998) used morphological and genetic data to elevate E. guttolineata to full species. Furthermore, Carlin’s analysis was capable of unambiguously identifying individuals from the putative zone of intergradation (located in northern Alabama and Georgia), making uncertain the status of hybrids that previously had been described based solely on morphological characters. There are also reports of zones of sympatry along Blue Ridge escarpment that lack apparent intergradation (Ireland, 1979; T.J.R. and R.C. Bruce, personal observations).
L. Age/Size at Reproductive Maturity. Maturation is synchronous between the sexes, coming at about 2-yr post hatching (Marshall, 1999; Ryan and Bruce, 2000). Females are slightly larger than males on average (Gordon, 1953).
M. Longevity. Unknown. Because of significant differences in the size at maturation and average (not to mention maximum) adult sizes (Ryan and Bruce, 2000), it is reasonable to believe that there is the potential for substantial post-maturation growth. Marshall (1999) was able to measure post-metamorphic growth in a population of three-lined salamanders and found that following maturation, growth slowed considerably (from 1.7 mm SVL/mo to 0.11 mm SVL/mo). If this is consistent across populations, then it is likely that some adult three-lined salamanders must survive for upwards of a decade or more.
N. Feeding Behavior. Three-lined salamanders feed on a variety of invertebrate prey including snails, snail eggs, arachnids, millipedes, annelids, nematodes, and insects including hymenopterans (especially ants), dipterans, coleopterans, orthopterans, hemipterans, homopterans, lepidopterans, neuropterans, odonates, collembolans, and trichopterans (Tinkle, 1952; Petranka, 1998).
O. Predators. Unknown. It is easy to speculate that inhabitants of water edges and forest floors (e.g., semi-aquatic and/or semi-fossorial snakes and small mammals such as voles and shrews) and larger salamanders are likely important predators.
P. Anti-Predator Mechanisms. Three-lined salamanders assume a classic urodelean defensive posture that includes coiling their body, tucking their head beneath their tail, and raising and undulating their tail (Brodie, 1977).
Q. Diseases. Unknown.
R. Parasites. Rankin (1937) lists the following parasites from three-lined salamanders: Protozoa—Cryptobia borreli, Cytamoeba bacterifera, Eutrichomastix batrachorum, Haptophyra michiganensis, Hexamastix batrachorum, Hexamitus batrachorum, Prowazekella longifilis, and Tritrichomonas augusta; Trematoda—Batrachycoelium hospitale and Gorgoderina tenua; Nematoda—Oxyuris magnavulvaris and spirurid cysts; Cestoda—proteocephalid cysts; Acarina—Hannemania dunni.
4. Conservation. Three-lined salamanders remain abundant throughout much of their range, and there is no evidence to support a difference between the current and historical distributions. While the loss of bottomland hardwood forests throughout the Southeast has undoubtedly resulted in the extirpation of many populations (Petranka, 1998), direct links between habitat loss and population declines have not been demonstrated.
1Travis J. Ryan
2Brooke A. Douthitt
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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