The four-toed salamander is thought to be in a state of decline throughout its range due primarily to its specialized habitat requirements in conjunction with destruction, degradation, and fragmentation of wetlands and forests. Even in the north and east, where the four-toed salamander's range is more continuous, it only occurs is small isolated colonies where suitable wetland-woodland interfaces exist. Additionally, the low dispersal ability of this salamander hinders it from recolonizing suitable habitat once it has been extirpated from an area (Harding 1997).
Hemidactylium scutatum is currently listed as endangered in Indiana and Minnesota, threatened in Illinios, and has special concern or rare status in Wisconsin, Ohio, and Missouri (Lannoo 1998). To improve conservation efforts, people should be educated on the vulnerability and value of the species.
To improve and increase habitat for the four-toed salamander, mature, closed canopy, mesic hardwood forests should be preserved. Downed woody debris should be left in place or added to these forests. Shallow vernal pools can be created within these woodlands and raised hummucks of earth can be added in and around the pool to promote growth of spagnum moss and sedges (Petranka 1998). The creation of suitable habitat between two populations, or "corridors," could also be investigated where two fragmented populations in close proximity exist.
Individuals are likely killed crossing roads while migrating to and from breeding sites. As a preventative measure, "'critter-culverts" can be installed in areas of high road kill risk to allow salamanders to pass underneath roads to and from their breeding sites.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
The four-toed salamander is a small plethodontid (lungless) salamander only 5 to 10.2 cm (2 to 4 in) in length. It is a rusty brown color or gray-brown color with grayish sides. It is often speckled with black and bluish spots. Unique four-toed hind feet and a constricted ring around the base of its tail easily identify it. They have nasolabial grooves and 13 to 14 coastal grooves (Harding 1997). The tail makes up about 57 percent of its total body length (Petranka 1998).
Female four-toed salamanders have rounded snouts, while sexually active males have more squared (truncated) snouts. Enlarged premaxillary teeth are also evident in sexually active males and can be seen with a closed mouth. The snout-to-vent length (SVL) is approximately 15 percent longer in females than males (Petranka 1998).
Hatchlings are only 11 to 15 mm total body length. They are usually born with toes or toe buds. The larvae are aquatic and a yellowish brown color. A dorsal fin runs from the length of the tail to near the back of the head. Some hatchlings look more like adults but have shorter tails (Petranka 1998).
Other Physical Features: ectothermic ; bilateral symmetry
Average lifespan
Sex: female
Status: captivity: 5.5 years.
Four-toed salamanders have specialized habitat requirements which require suitable breeding wetlands within or adjacent to mature forests. They prefer mature, mesic forests with dense canopy cover to preserve body moisture, an abundance of downed woody debris for cover and foraging opportunities, and vernal pools, ponds, bogs, shallow marshes, or other fishless bodies of water for nesting and larval success. Wooded wetlands such as seepage swamps or cedar swamps with many moss mats are ideal. Male adults can be located under leaves, bark, and logs in the upland forest, while females are most often found during the breeding season nesting in moss mats which overhang pools of water. (Harding 1997, Petranka 1998).
Terrestrial Biomes: forest
Hemidactylium scutatum, the four-toed salamander, occurs from Nova Scotia to northern Minnesota, and south to the Gulf of Mexico. It has a discontinuous range and occurs only in small isolated populations in the southern and midwestern states. Its range is more continuous in states along the Appalachian Mountain Range, New England and west to northeastern Minnesota. (Behler and King 1979, Conant and Collins 1998, Lannoo 1998).
Biogeographic Regions: nearctic (Native )
Few studies have been conducted on the feeding habits of the four-toed salamander, but it is believed their diet consists mainly of insects and their larvae (beetles, flies, ants, bristletails), spiders, mites, worms, and snails (Harding 1997, Petranka 1998).
Forest dwelling salamanders, in general, have been shown to be very important contributers to nutrient cycling and energy flow in forest ecosystems. Therefore, they are important for the health and balance of forest systems as both predator and prey. A study in New Hampshire showed that forest salamanders act as sinks for high quality nutrients such as calcium and their tissue is higher in protein than birds or mammals. Additionally, their collective biomass may be twice that of birds and around the same as small mammals (Burton 1975a, 1975b). While Four-toed salamanders alone are not this abundant, it is likely that they contribute similarly to the food web in many forests where they are plentiful.
Their diet of calcium rich invertebrates makes them nutritious meals for shrews, snakes, birds, fish, and other carnivores which likely feed on four-toed salamanders (Burton 1975b, Harding 1997).
Four-toed salamanders are harmless, slow moving, colorful creatures of our forests and wetlands and are can be an interesing find for the casual naturalist or small child. The asthetic niche these creatures hold makes outdoor recreation more valuable to many.
The four-toed salamander is completely harmless to humans and their interests.
Development - Life Cycle: metamorphosis
PLEISTOCENE GLACIATION AND DISJUNCT DISTRIBUTION:
Hemidactylium scutatum occures only in small isolated populations in Illinois, Indiana, Kentucky, Missouri, Arkansas, Oklahoma, Louisiana, Mississippi, Alabama, and Florida. These disjunct populations in the southern and midwestern states are thought to be relict populations left during the post pleistocene glacier retreats. As glaciers moved south during the Pleistocene period the climate cooled and terrestrial animals were gradually forced into warmer refugia in the south. Later, as the glaciers retreated north, barriers such as prairies and deforested areas were created. These barriers stranded populations of animals with low disperal ability and specialized habitat requirements, such as H. Scutatum, and they were left stranded in isolated pockets of suitable habitat. (Lannoo 1998).
EVOLUTION:
The four-toed salamander is a lungless salamander of the Plethodontidae family. All plethodontids are lungless, breathe through their skin, and most are completely terrestrial. However, the four-toed salamander belongs to the tribe Hemidactyliini of the Plethodontinae subfamily. Members of this tribe are the only plethodontids to have an aquatic larval stage and are thought to have split from an earlier line of plethodontids. This suggests the four-toed salamander is a very primitive plethodontid and more closely related to the lunged Ambistomatidae family, or mole salamanders (Wake 1966).
It has been long hypothosized that plethodontid salamanders, evolved in the Appalachian Mountains, slowly losing their lungs in order to reduce buoyancy, become stream-lined, sink easily, and grasp stream bottoms. This allowed them to avoid being carried downstream, away from their habitat, by swift mountain currents.
Due to recent evidence that the Appalachian region was not mountainous at the time of plethodontid evoluion, this hypothesis has been challenged and a debate has developed. Alternative selective mechanisms for lung loss, such as selection for narrower heads and increased prey-capture abilities, have been suggested. The outcome of this debate will be significant in determining the correct phylogenetic relationships of the four-toed salamander and other plethodontids (Beechy and Bruce 1992, Wake 1966).
Mating occurs in the late summer, fall, and possibly into early winter in some places. The male courts the female first by rubbing his nose on the female's nose, then he will circle around her with his tail bend at a sharp right angle. At some point the female straddles the male's tail and presses her snout on the base of his tail. Eventually the male starts moving forward, undulating his tail, and begins depositing spermatophores, while the female follows him at a close distance. The spermatophores are a jelly-like glob that are about 2mm wide at the base and tapers to a thin stalk, which is topped with a yellowish sperm cap. The female picks up the spermatophores and deposits them into her cloaca while pressing her snout against the male's tail. This "straddle walk" lasts for up to 20 minutes (Harding 1997, Petranka 1998).
Female four-toed salamanders migrate to nesting sites primarily from the last week of March through the second week of April, but may wait until as late as early June. Oviposition occurs from mid to late April in Michigan, but can occur as late as February in southern Alabama. Females seek out moss clumps that are just above a pool of water usually in swamps, bogs, marshes, vernal ponds, and slow moving streams. The nesting medium is usually raised clumps of sphagnum moss, but leaf litter, rotting logs, or grass and sedge clumps are also used. The female then locates or constructs a cavity to deposit her eggs, which takes several minutes for each one and may take several hours for the whole clutch. The eggs have a sticky outer coating, which she uses to adhere to the surrounding moss. Fifteen to 80 eggs, each between 2.5 and 3.0 mm in diameter, are laid. More eggs tend to be laid by larger females (Harding 1997, Oliver 1955, Petranka 1998). Females often share nests and as many as 1110 eggs have been found in a single nest (Blanchard 1934). Nest availability is thought to be a factor in this communal nesting behavior (Breitenbach 1982). Often one or more (usually one) female will stay with the nest for a period, but they are usually gone by hatching. Despite a lack of defensive behavior toward invading predators, the female's nest attendance has been found to increase embryo survival (Carreno and Harris 1998). It is believed that the mother's skin secretions may protect the eggs by impeding fungus growth. So far, no beneficial link has been established between joint nesting and embryo survival (Harris and Gill 1980). The incubation period varies from 38 to 62 days depending upon the region and local site conditions. Average survivorship after hatching has been estimted at 9 and 21 percent (Harding 1997, Petranka 1998).
After hatching the larva wiggle from their nest and drop into the nearby water. They are only about 1.1 to 1.4 cm total body length at birth. During this larval stage they feed primarily on zooplankton and other invertebrates. Their larval period lasts between 23-39 days, which is brief compared to other amphibians. At transformation they are only 1.7 to 2.5 cm total body length (Harding 1997, Petranka 1998). The sex ratio of juveniles is nearly equal (Blanchard 1935).
It takes between two and three years for H. scutatum to reach sexual maturity. Captive specimens have lived as long as nine years but it is unknown how long free-ranging individuals may survive (Harding 1997).
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)
Average number of offspring: 30.
Average age at sexual or reproductive maturity (male)
Sex: male: 912 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 912 days.
Despite their susceptibility to desiccation and use of the forest floor, evidence as of 2008 suggests that most salamanders typically avoid direct effects of fire by retreating to underground burrows or moist refugia [67,77,82]. Capture rates of 4 Plethodontid salamander species in southwestern North Carolina were not significantly altered following a spring prescribed fire [39]. Characteristics of salamander communities, such as richness, abundance, and diversity, were not significantly affected by spring prescribed fire in a Piedmont upland woodland in South Carolina [38] or winter prescribed fire in bottomland hardwood forest in Georgia [71]. Relative abundance of salamanders in a southern Appalachian upland hardwood forest in South Carolina was not significantly different between plots that were burned under prescription, had the understory removed before prescribed burning, or were untreated [43]. Relative abundance of amphibians on oak-dominated stands of the Virginia Piedmont, including eastern red-back salamanders, was not significantly different between unburned and fall-, winter-, or spring-burned sites [61].
However, fewer captures of salamanders on burned sites compared to unburned sites [38,44,69,70] and mortalities of eastern red-backed salamanders sheltering under dead logs [70] indicate the potential for negative effects of fire on adult four-toed salamanders. Four-toed salamanders have not been observed on recently burned sites. On the Atlantic coastal plain in Maryland, 20 four-toed salamanders were captured in unburned pine-mixed-hardwood habitat, while none was captured in a repeatedly burned loblolly pine site. This difference was statically significant (P<0.01). The burned site was the same distance as the unburned site from a marshy area likely used for nesting, but it was 790 feet (240 m) farther from the nearest wetland than the unburned site [69]. Unmanaged mixed-hardwood stands had higher amphibian relative abundance and surface activity than 2 regularly but infrequently burned pine plantations in South Carolina [44].
According to a review, aquatic life stages of salamanders are typically sheltered from direct effects of fire, so mortality is rarely documented [77]. However, larval mortality could occur if water was heated to lethal temperatures or if temperatures reached stressful levels, likely above 77 °F (25 °C) [88], for several hours. Heat can also lead to lethal chemical changes in water [77].
Fires occurring during inactive periods such as late summer or winter would likely be least detrimental to four-toed salamanders, since use of underground burrows is more common during these periods (see Cover Requirements). The use of moist sites suggests that four-toed salamander eggs are seldom exposed to lethal fires. The higher surface-to-volume ratio of juveniles makes them more susceptible to drying [37,88]. Therefore, juveniles may be even more restricted to moist environments than adults [5,37] and may be exposed to fire less often than adults.
Effects on aquatic habitat: Fire can have beneficial or detrimental impacts on the availability of nesting sites and larval pools, wetlands, and ponds. According to a review, fires can prevent succession of aquatic habitats such as bogs to hardwood forest; succession would reduce water levels and, presumably, available larval habitat [82]. Reduction in vegetation also reduces evapotranspiration, raising water levels and providing more potential larval habitat [77]. Woody debris that falls following fire can create new pools for nesting and larval habitat [56]. However, consumption of nesting vegetation and other substrates by fire would likely negatively impact habitat, particularly because of four-toed salamander's apparent fidelity to nesting ponds [50].
If erosion and sedimentation occur following fire, availability of breeding sites may be reduced temporarily. The California newt (Taricha torosa), a species that nests in deep, slow-moving water, laid fewer egg masses following a chaparral wildfire that reduced the number of runs and pools in a nesting stream [41]. A review suggests that impacts of sedimentation on nesting habitat may be greater in streams with low gradients [34], such as those used by four-toed salamander larvae [88]. According to a review, sediment in streams can reach 100 times typical levels and persist for over 10 years following severe fires. Nevertheless, effects of fire and the resulting sedimentation on pond-breeding amphibians could be negligible in most circumstances [77].
Characteristics of larval habitats that may be impacted by fire include temperature, nutrient input, productivity, pH, evaporation rate, morphology, and water-holding capacity [34,74,77]. Reviews suggest that fire typically results in a temporary increase in pH [64,72]. This could potentially benefit acid-sensitive species [84]. Although four-toed salamanders can occur in acidic water, they may be sensitive to low pH (see Aquatic habitats). Characteristics of temporary ponds, including pH, were not significantly altered by prescribed fire on low-elevation sites of South Carolina [84].
Effects on terrestrial habitatFire often reduces leaf litter and other ground cover in salamander habitat [43,61,62,69,71,84]. A mixed pine-hardwood site occupied by four-toed salamander had significantly greater litter depth than an unoccupied burned site on the Atlantic coast plain of Maryland [69]. Similar changes have been observed following fire in other areas within the four-toed salamander's distribution. In south-central Pennsylvania, average litter cover the spring following a fall fire was 52.3%, and the litter layer averaged 0.5 inch (1.15 cm) deep, compared to 76.8% average litter cover and an average litter depth of 2.8 inches (7.15 cm) on an adjacent unburned site. Living ground cover was also reduced, with the unburned site having 13.7% cover of shrubs and mosses and the burned site lacking living ground cover. On the burned site cover of mineral soil was 27.6%, while on the unburned site it was only 0.1% [62]. In bottomland hardwood forests in Georgia, litter was significantly deeper (P<0.025) and percent cover of bare ground was significantly smaller (P<0.003) on unburned plots compared to burned plots [71]. Prescribed fires and understory removal followed by prescribed fires resulted in significantly (P<0.0001) reduced leaf litter compared to untreated plots in southern Appalachian upland hardwood forest in North Carolina [43].
Loss of leaf litter may also affect four-toed salamanders by reducing the availability of prey. If four-toed salamanders feed only in wet litter, as is the case with eastern red-backed salamanders [58], reduction of leaf litter likely reduces foraging habitat. Reductions in leaf litter associated with timber harvesting resulted in a decline in the abundance of macroarthropods in the leaf litter in the southern Appalachians [85]. See Food Habits for a discussion of the possible repercussions of reduced food availability on four-toed salamanders.
The litter that accumulates within a few years of a disturbance apparently provides adequate habitat for salamanders, suggesting that impacts to certain four-toed salamander habitat features may be short lived. In northern hardwoods of New Hampshire the amount of leaf litter increased from nearly zero to as much as 20% of precutting levels within 4 years of clearcutting [28]. Plethodontid salamanders in the southern Blue Ridge Mountains of North Carolina were detected in clearcut stands 4 to 6 years after harvesting, which coincided with development of the litter layer [5]. Differences in leaf litter depth between burned and control sites in a southern Appalachian deciduous forest in eastern Tennessee were no longer significant 3 years following fire [40]. Living ground cover was similar in burned and unburned vegetation by the end of the summer following a fall fire in south-central Pennsylvania [62].
Moss provides cover, foraging habitat, and nesting habitat for four-toed salamanders on many sites, so the impact of fire on moss will likely influence four-toed salamanders. Recovery of moss following fire varies with species [2,63]. For instance, juniper haircap moss (Polytrichum juniperinum) can colonize sites within 4 years of fire, while late-successional species such as splendid feather moss (Hylocomium splendens) may take over 50 years to reach prefire levels. A bog in western Canada experienced substantial colonization of upright haircap moss (Polytrichum strictum) within 2 years of fire, with greater colonization in low, wet areas. Colonization of upright haircap moss appeared to facilitate the establishment of sphagnum mosses [7]. Mosses often used by four-toed toed salamander are discussed in Nest sites.
Effects on coarse woody debris: Reduction in coarse woody debris due to fire may negatively impact four-toed salamanders. A loblolly pine stand in Maryland that was repeatedly burned under prescription had significantly (P<0.05) less coarse woody debris and significantly (P<0.01) fewer four-toed salamanders than an unburned mixed pine-hardwood stand [69].
The consistent moisture levels of coarse woody debris may provide refuge for salamanders following fires that consume substantial amounts of leaf litter. Presence of coarse woody debris following disturbance may be especially important on dry sites [71,75]. As of 2008, information on loss of large amounts of coarse woody debris from wildfire in salamander habitats in the eastern United States was lacking; most of the studies described here investigate the impacts of low-severity fires [43,61,71].
Some fires increase coarse woody debris and could increase nesting habitat by blocking streams, forming pools and/or providing substrates where females can lay eggs. Following a mixed-severity wildfire in western Montana, potential long-toed salamander (Ambystoma macrodactylum) breeding sites increased due to fallen trees blocking intermittent streams and creating new pools [56].
Effects on canopy cover: Increases in solar radiation could reduce habitat quality for four-toed salamanders (see Canopy cover). The significant (P<0.05) reductions in canopy cover and deciduous tree density on repeatedly burned loblolly pine sites in Maryland were suggested as possible explanations for four-toed salamander absence from the repeatedly burned sites [69]. Increased light may reduce habitat quality due to higher temperatures, greater UV-B exposure [77], and drier vegetation around ponds. However, increased productivity and longer hydroperiods due to reduced evapotranspiration following reduction in canopy cover could potentially benefit salamanders [87]. For more information, see Aquatic habitats.
Landscape-scale considerations: Reduction in four-toed salamander microhabitats could interfere with successful migration into nesting ponds and/or dispersal between populations. Desiccation and predation likely pose greater risks to salamanders migrating or dispersing through burned habitat than to those in unburned habitat [20,77,84]. The consistent use of the same nesting ponds by four-toed salamanders in northern Virginia [50] and the generally low mobility of salamanders suggest obstructions to movement could compromise the long-term persistence of four-toed salamanders at a given site [69].
Landscape-scale factors such as distance to water and topography may have greater influences on salamanders than fire. Distance to water and mesic aspects were significantly (P≤0.032) associated with eastern red-backed salamander captures in oak-dominated forest in the Virginia Piedmont, while fire treatments were not [61]. Slope location had more impact on salamander abundance in southwestern North Carolina than prescribed fire treatments. This may be partly related to differences in severity on different parts of the slope (see next paragraph) [39].
Fire Characteristics: Although high-severity fires are rare in the moist habitats occupied by four-toed salamanders (see Fire Ecology), they would likely have large, long-term impacts. Little of the current information on salamanders' response to fire is based on high-severity fires [38,71]. Although a fire in southwestern North Carolina was severe in upland areas, in midslope and riparian areas the fire consumed comparatively little vegetation [39]. The most severe fire in a southern Appalachian upland hardwood forest resulted in 25% tree mortality and insignificant impacts on coarse woody debris or duff depths [43]. High-severity fires would be more likely to consume coarse woody debris, burn deep into litter and duff, and reduce canopy cover. Many shelters would likely be consumed, leaving salamanders more vulnerable to overheating or desiccation. After a fire in the Jemez Mountains of New Mexico, 24-hour average daily temperatures in potential salamander shelters were much higher in areas burned in high-severity and moderate-severity fires than those burned in low-severity fires [31]. For a discussion of the effect of canopy removal and ground disturbance on four-toed salamanders, see Forest management.
It has been suggested that large wildfires that occur during dry periods, when salamanders are generally limited to damp areas or underground burrows, may have less impact on salamanders than prescribed fires that are more likely to occur in moist or humid conditions when salamanders are active [21]. Fire during periods of four-toed salamander activity, such as the spring migratory and nesting and fall breeding seasons, could result in greater mortality due to more individuals being caught in exposed areas or migrating through recently burned areas [77,84]. However, season of burning (spring, winter, or summer) did not influence eastern red-back salamanders or amphibians in general in shelterwood-harvest oak forests of the Virginia Piedmont [61].
Frequent fires are likely to have greater impacts on four-toed salamanders and their habitat than single or infrequent fires [38,69]. A loblolly pine site that burned 5 or 6 times in 11 years had significantly fewer four-toed salamanders than a nearby unburned pine-mixed hardwood site. Repeated burning likely explains the significant (P<0.05) reductions in habitat characteristics important to salamanders such as coarse woody debris and canopy cover [69]. Data from timber harvesting studies suggest that long return-intervals of severe disturbances would minimize impacts on salamanders [55] and the litter layer [1].
Fire Ecology and FIRE REGIMES: Four-toed salamanders occur in forests with varied FIRE REGIMES (see the Fire Regime Table of plant communities with four-toed salamanders). Their association with moist areas near pools, streams, and other aquatic habitats suggests that their habitat would generally burn less frequently than upland forest types. Drought likely increases the risk of fire in four-toed salamander habitat. For more information on FIRE REGIMES within the four-toed salamander's range, see the FEIS reviews of the dominant plant species in four-toed salamander habitats, such as pitch pine, eastern white pine, white oak, and sugar maple (Acer saccharum), and the Fire Regime Table. Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Status: Little is known regarding four-toed salamander population trends. A population in Great Smoky Mountains National Park appeared stable, but much more data were needed to detect population change [27]. A review of four-toed salamander in Wisconsin notes four-toed salamander rarity and suggests that more information, including basic data on distribution, is needed [92].
Threats: According to reviews, major threats to four-toed salamanders are the loss, degradation, and fragmentation of habitat [88]. Reduction of hydroperiods, decreases in pH of ponds, and increases in water temperature and sedimentation can have negative impacts on four-toed salamander larvae [17,88]. For more information on the direct and indirect effects of changes to water quality, see Bol and others [17]. Removal or compaction of living and dead ground cover limits the availability of adult habitat. Fragmentation could restrict movement to breeding grounds and between populations [17]. Roads may pose dispersal barriers and result in substantial mortality if located along migration routes [17,34,83]
For speculation on possible effects of climate change on four-toed salamanders in Nova Scotia, see Herman and Scott [52].
Forest management: Reduced cover of canopy trees, leaf litter, and well-decayed coarse woody debris likely contribute to the negative response and long recovery times of salamanders after timber harvesting. Detrimental effects of tree harvesting on salamanders have been documented in the southern Appalachians [5,46,55,75,76], Pennsylvania [81], and New York [78]. In low-elevation hardwood forests of southwestern Virginia, terrestrial salamanders were significantly reduced following a clearcut (P=0.001), a leave-tree (P=0.001), a group selection (P=0.005), and 2 shelterwood (P=0.005) treatments, while terrestrial salamander abundance did not change on untreated sites or sites where the understory was removed with herbicide. Canopy cover and leaf litter cover were greatest on the control and the understory removal treatments. These plots also had higher leaf litter moisture and cooler soil temperatures [46]. In Pennsylvania there was a significant positive relationship (P=0.01) between retained basal area of harvested stands and salamander species richness. The relative abundance of salamanders also increased significantly (P<0.001) with increasing basal areas greater than 15 m²/ha [81]. In the southern Blue Ridge Mountains of North Carolina, Plethodontid salamanders were reduced by 30% to 50% in the 1st year and nearly 100% by the 2nd year following clearcutting. Recovery of salamanders began 4 to 6 years following timber harvesting and seemed correlated with litter layer development. Projections based on up to 15 years of data collected after timber harvesting in the southern Blue Ridge Mountains suggest that salamanders would reach predisturbance levels from 20 to 24 years following clearcutting [5]. Estimated recovery times in western North Carolina were more than 50 years [75,76]. In hardwood stands in New York, recently disturbed stands had significantly (P<0.05) fewer eastern red-backed salamanders than adjacent old-growth controls, while abundance was similar on old-growth and 60-year-old second-growth stands [78]. DeMaynadier and Hunter [34] provide a comprehensive review of salamander responses to timber harvesting based on the literature as of 1995.
Effects of logging on four-toed salamanders may be mitigated to varying extents by minimizing the extent of thinning [17,81]; incorporating undisturbed buffer strips around wetlands, ponds, and streams; reducing impacts to microhabitats such as moss and grass tussocks, leaf litter, and coarse woody debris; and reducing soil compaction by limiting disturbance to periods when soils are frozen or dry [17,34,75,83]. For specific recommendations for timber harvesting in four-toed salamander habitat in the Northeast, see Bol and others [17].
Protecting breeding habitat and surrounding mature forest has been suggested to maintain salamander populations from disturbance [25,34,69,75]. Several sources note the importance of maintaining complexes of mature forests used by adults and the pools and wetlands used by larvae in a mosaic that allows for movement between adult and larval habitat as well as dispersal between nesting areas [17,25,27,69]. FIRE EFFECTS AND MANAGEMENT SPECIES: Hemidactylium scutatumPrescribed fire on the Nantahala National Forest, North Carolina. USDA Forest Service photo.
Several of the studies discussed below have limitations due to small sample sizes, short-term study periods, little or no replication, no prefire data, and/or no controls [77,82]. Reviews of the effect of fire on amphibians from 1999 [82] and 2003 [77] are frequently cited in this section.
DIRECT FIRE EFFECTS:However, fewer captures of salamanders on burned sites compared to unburned sites [38,44,69,70] and mortalities of eastern red-backed salamanders sheltering under dead logs [70] indicate the potential for negative effects of fire on adult four-toed salamanders. Four-toed salamanders have not been observed on recently burned sites. On the Atlantic coastal plain in Maryland, 20 four-toed salamanders were captured in unburned pine-mixed-hardwood habitat, while none was captured in a repeatedly burned loblolly pine site. This difference was statically significant (P<0.01). The burned site was the same distance as the unburned site from a marshy area likely used for nesting, but it was 790 feet (240 m) farther from the nearest wetland than the unburned site [69]. Unmanaged mixed-hardwood stands had higher amphibian relative abundance and surface activity than 2 regularly but infrequently burned pine plantations in South Carolina [44].
According to a review, aquatic life stages of salamanders are typically sheltered from direct effects of fire, so mortality is rarely documented [77]. However, larval mortality could occur if water was heated to lethal temperatures or if temperatures reached stressful levels, likely above 77 °F (25 °C) [88], for several hours. Heat can also lead to lethal chemical changes in water [77].
Fires occurring during inactive periods such as late summer or winter would likely be least detrimental to four-toed salamanders, since use of underground burrows is more common during these periods (see Cover Requirements). The use of moist sites suggests that four-toed salamander eggs are seldom exposed to lethal fires. The higher surface-to-volume ratio of juveniles makes them more susceptible to drying [37,88]. Therefore, juveniles may be even more restricted to moist environments than adults [5,37] and may be exposed to fire less often than adults.
HABITAT RELATED FIRE EFFECTS:Effects on aquatic habitat: Fire can have beneficial or detrimental impacts on the availability of nesting sites and larval pools, wetlands, and ponds. According to a review, fires can prevent succession of aquatic habitats such as bogs to hardwood forest; succession would reduce water levels and, presumably, available larval habitat [82]. Reduction in vegetation also reduces evapotranspiration, raising water levels and providing more potential larval habitat [77]. Woody debris that falls following fire can create new pools for nesting and larval habitat [56]. However, consumption of nesting vegetation and other substrates by fire would likely negatively impact habitat, particularly because of four-toed salamander's apparent fidelity to nesting ponds [50].
If erosion and sedimentation occur following fire, availability of breeding sites may be reduced temporarily. The California newt (Taricha torosa), a species that nests in deep, slow-moving water, laid fewer egg masses following a chaparral wildfire that reduced the number of runs and pools in a nesting stream [41]. A review suggests that impacts of sedimentation on nesting habitat may be greater in streams with low gradients [34], such as those used by four-toed salamander larvae [88]. According to a review, sediment in streams can reach 100 times typical levels and persist for over 10 years following severe fires. Nevertheless, effects of fire and the resulting sedimentation on pond-breeding amphibians could be negligible in most circumstances [77].
Characteristics of larval habitats that may be impacted by fire include temperature, nutrient input, productivity, pH, evaporation rate, morphology, and water-holding capacity [34,74,77]. Reviews suggest that fire typically results in a temporary increase in pH [64,72]. This could potentially benefit acid-sensitive species [84]. Although four-toed salamanders can occur in acidic water, they may be sensitive to low pH (see Aquatic habitats). Characteristics of temporary ponds, including pH, were not significantly altered by prescribed fire on low-elevation sites of South Carolina [84].
Effects on terrestrial habitatFire often reduces leaf litter and other ground cover in salamander habitat [43,61,62,69,71,84]. A mixed pine-hardwood site occupied by four-toed salamander had significantly greater litter depth than an unoccupied burned site on the Atlantic coast plain of Maryland [69]. Similar changes have been observed following fire in other areas within the four-toed salamander's distribution. In south-central Pennsylvania, average litter cover the spring following a fall fire was 52.3%, and the litter layer averaged 0.5 inch (1.15 cm) deep, compared to 76.8% average litter cover and an average litter depth of 2.8 inches (7.15 cm) on an adjacent unburned site. Living ground cover was also reduced, with the unburned site having 13.7% cover of shrubs and mosses and the burned site lacking living ground cover. On the burned site cover of mineral soil was 27.6%, while on the unburned site it was only 0.1% [62]. In bottomland hardwood forests in Georgia, litter was significantly deeper (P<0.025) and percent cover of bare ground was significantly smaller (P<0.003) on unburned plots compared to burned plots [71]. Prescribed fires and understory removal followed by prescribed fires resulted in significantly (P<0.0001) reduced leaf litter compared to untreated plots in southern Appalachian upland hardwood forest in North Carolina [43].
Loss of leaf litter may also affect four-toed salamanders by reducing the availability of prey. If four-toed salamanders feed only in wet litter, as is the case with eastern red-backed salamanders [58], reduction of leaf litter likely reduces foraging habitat. Reductions in leaf litter associated with timber harvesting resulted in a decline in the abundance of macroarthropods in the leaf litter in the southern Appalachians [85]. See Food Habits for a discussion of the possible repercussions of reduced food availability on four-toed salamanders.
The litter that accumulates within a few years of a disturbance apparently provides adequate habitat for salamanders, suggesting that impacts to certain four-toed salamander habitat features may be short lived. In northern hardwoods of New Hampshire the amount of leaf litter increased from nearly zero to as much as 20% of precutting levels within 4 years of clearcutting [28]. Plethodontid salamanders in the southern Blue Ridge Mountains of North Carolina were detected in clearcut stands 4 to 6 years after harvesting, which coincided with development of the litter layer [5]. Differences in leaf litter depth between burned and control sites in a southern Appalachian deciduous forest in eastern Tennessee were no longer significant 3 years following fire [40]. Living ground cover was similar in burned and unburned vegetation by the end of the summer following a fall fire in south-central Pennsylvania [62].
Moss provides cover, foraging habitat, and nesting habitat for four-toed salamanders on many sites, so the impact of fire on moss will likely influence four-toed salamanders. Recovery of moss following fire varies with species [2,63]. For instance, juniper haircap moss (Polytrichum juniperinum) can colonize sites within 4 years of fire, while late-successional species such as splendid feather moss (Hylocomium splendens) may take over 50 years to reach prefire levels. A bog in western Canada experienced substantial colonization of upright haircap moss (Polytrichum strictum) within 2 years of fire, with greater colonization in low, wet areas. Colonization of upright haircap moss appeared to facilitate the establishment of sphagnum mosses [7]. Mosses often used by four-toed toed salamander are discussed in Nest sites.
Effects on coarse woody debris: Reduction in coarse woody debris due to fire may negatively impact four-toed salamanders. A loblolly pine stand in Maryland that was repeatedly burned under prescription had significantly (P<0.05) less coarse woody debris and significantly (P<0.01) fewer four-toed salamanders than an unburned mixed pine-hardwood stand [69].
The consistent moisture levels of coarse woody debris may provide refuge for salamanders following fires that consume substantial amounts of leaf litter. Presence of coarse woody debris following disturbance may be especially important on dry sites [71,75]. As of 2008, information on loss of large amounts of coarse woody debris from wildfire in salamander habitats in the eastern United States was lacking; most of the studies described here investigate the impacts of low-severity fires [43,61,71].
Some fires increase coarse woody debris and could increase nesting habitat by blocking streams, forming pools and/or providing substrates where females can lay eggs. Following a mixed-severity wildfire in western Montana, potential long-toed salamander (Ambystoma macrodactylum) breeding sites increased due to fallen trees blocking intermittent streams and creating new pools [56].
Effects on canopy cover: Increases in solar radiation could reduce habitat quality for four-toed salamanders (see Canopy cover). The significant (P<0.05) reductions in canopy cover and deciduous tree density on repeatedly burned loblolly pine sites in Maryland were suggested as possible explanations for four-toed salamander absence from the repeatedly burned sites [69]. Increased light may reduce habitat quality due to higher temperatures, greater UV-B exposure [77], and drier vegetation around ponds. However, increased productivity and longer hydroperiods due to reduced evapotranspiration following reduction in canopy cover could potentially benefit salamanders [87]. For more information, see Aquatic habitats.
Landscape-scale considerations: Reduction in four-toed salamander microhabitats could interfere with successful migration into nesting ponds and/or dispersal between populations. Desiccation and predation likely pose greater risks to salamanders migrating or dispersing through burned habitat than to those in unburned habitat [20,77,84]. The consistent use of the same nesting ponds by four-toed salamanders in northern Virginia [50] and the generally low mobility of salamanders suggest obstructions to movement could compromise the long-term persistence of four-toed salamanders at a given site [69].
Landscape-scale factors such as distance to water and topography may have greater influences on salamanders than fire. Distance to water and mesic aspects were significantly (P≤0.032) associated with eastern red-backed salamander captures in oak-dominated forest in the Virginia Piedmont, while fire treatments were not [61]. Slope location had more impact on salamander abundance in southwestern North Carolina than prescribed fire treatments. This may be partly related to differences in severity on different parts of the slope (see next paragraph) [39].
Fire Characteristics: Although high-severity fires are rare in the moist habitats occupied by four-toed salamanders (see Fire Ecology), they would likely have large, long-term impacts. Little of the current information on salamanders' response to fire is based on high-severity fires [38,71]. Although a fire in southwestern North Carolina was severe in upland areas, in midslope and riparian areas the fire consumed comparatively little vegetation [39]. The most severe fire in a southern Appalachian upland hardwood forest resulted in 25% tree mortality and insignificant impacts on coarse woody debris or duff depths [43]. High-severity fires would be more likely to consume coarse woody debris, burn deep into litter and duff, and reduce canopy cover. Many shelters would likely be consumed, leaving salamanders more vulnerable to overheating or desiccation. After a fire in the Jemez Mountains of New Mexico, 24-hour average daily temperatures in potential salamander shelters were much higher in areas burned in high-severity and moderate-severity fires than those burned in low-severity fires [31]. For a discussion of the effect of canopy removal and ground disturbance on four-toed salamanders, see Forest management.
It has been suggested that large wildfires that occur during dry periods, when salamanders are generally limited to damp areas or underground burrows, may have less impact on salamanders than prescribed fires that are more likely to occur in moist or humid conditions when salamanders are active [21]. Fire during periods of four-toed salamander activity, such as the spring migratory and nesting and fall breeding seasons, could result in greater mortality due to more individuals being caught in exposed areas or migrating through recently burned areas [77,84]. However, season of burning (spring, winter, or summer) did not influence eastern red-back salamanders or amphibians in general in shelterwood-harvest oak forests of the Virginia Piedmont [61].
Frequent fires are likely to have greater impacts on four-toed salamanders and their habitat than single or infrequent fires [38,69]. A loblolly pine site that burned 5 or 6 times in 11 years had significantly fewer four-toed salamanders than a nearby unburned pine-mixed hardwood site. Repeated burning likely explains the significant (P<0.05) reductions in habitat characteristics important to salamanders such as coarse woody debris and canopy cover [69]. Data from timber harvesting studies suggest that long return-intervals of severe disturbances would minimize impacts on salamanders [55] and the litter layer [1].
Fire Ecology and FIRE REGIMES: Four-toed salamanders occur in forests with varied FIRE REGIMES (see the Fire Regime Table of plant communities with four-toed salamanders). Their association with moist areas near pools, streams, and other aquatic habitats suggests that their habitat would generally burn less frequently than upland forest types. Drought likely increases the risk of fire in four-toed salamander habitat. For more information on FIRE REGIMES within the four-toed salamander's range, see the FEIS reviews of the dominant plant species in four-toed salamander habitats, such as pitch pine, eastern white pine, white oak, and sugar maple (Acer saccharum), and the Fire Regime Table. Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
FIRE
The lack of data addressing the impacts of fire on four-toed salamanders limits the generalizations that can be made regarding fire in four-toed salamander habitats. However, it is likely that low-severity, infrequent fires have few impacts on four-toed salamanders. Fires during or prior to active periods are likely to have greater impacts than fires at other times, since salamanders would be directly exposed to fire or recently burned habitats. It has been recommended that some portion of forests near nesting and larval habitat be maintained in an undisturbed, mature state to ensure the long-term persistence of salamanders, such as four-toed salamanders, with high nesting site fidelity and low dispersal ability that require cool, moist forest floors [44,69]. Prescribed burning may benefit some four-toed salamander larval habitats by increasing hydroperiods and food availability [77]. More information on four-toed salamander response to fires of varying severities are needed [77,82], including postfire dispersal ability and population-level effects of changes in microsite temperatures, litter and soil moisture levels, and water chemistry [77].
Due to potential negative impacts on amphibians, plowing firebreaks is discouraged around wetlands, and the Forest Service no longer uses retardants containing sodium ferrocyanide in riparian areas [9,77].
The four-toed salamander (Hemidactylium scutatum) is a lungless salamander native to eastern North America. It is the only species of the monotypic genus Hemidactylium.
The four-toed salamander can be recognized by its white underbelly sprinkled with black dots. Its back varies from orange-brownish to red-brownish; its flanks are grayish. The body and the limbs are elongated. The snout is short, and the eyes are prominent. The tail color is usually brighter than the back, and you can observe a constriction at the body/tail junction. The posterior limbs have four toes (hence its name), a good identification criterion but hard to use in the field. This species rarely exceeds 10 cm (3.9 in) in length. The sexes are alike except for the shape of the head. Males have elongated and almost square snouts, whereas the females' snouts are short and round. The juveniles show a tail shorter than the body.[2][3]
The four-toed salamander can be easily mistaken for the redback salamander (Plethodon cinereus) in the wild. The Four-toed salamander's underbelly is more of a "salt and pepper" color. There is no constriction at the tail, and posterior limbs show five digits.[2]
Mating occurs in terrestrial areas throughout the autumn months. In early spring the females nest on land, along the banks of small ponds. After the 4–6 week embryonic period, the larvae hatch and make their way to the adjacent pond. Four-toed salamanders undergo a relatively short aquatic larval period, when compared to other species of the same family, ranging between 3 and 6 weeks.[2][3][4]
The four-toed salamander has three main forms of self-defense against predators. The first is that it purposely sheds off its tail to distract the enemy. When the tail comes off, it is still wiggling around. The enemy gets distracted, giving the salamander time to get away. The second form of defense is playing dead. When threatened, this salamander will have a short burst of violent thrashes and then stop dead in its tracks. It will stay frozen like this until it feels the threat is gone (Sass and Anderson, 2011). The third and final form of defense is curling up and putting its tail on its back, offering it in exchange for its life.
There are three methods of nesting that have been documented in the females of H. scutatum, which can fall into one of two categories: solitary or communal/joint nesting. Solitary nesters lay and brood only their eggs. Communal nesting is normally one female brooding the eggs of two or more, up to 14, females of the same species. In this method the females either lay their eggs and leave the nest, or lay their eggs and stay to brood their eggs as well as those of the deserting females. About one-third of the nests of a population are joint nests, while between 50% and 70% of females lay their eggs in joint nests each year.[5][6]
Oophagy has also been reported in H.scutatum, where one female would eat several eggs of another female before laying her eggs in a communal nest.[5][6]
This species' favored habitats are sphagnum bogs, grassy areas surrounding beaver ponds, and deciduous or mixed forests rich with mosses. The four-toed salamander will use the sphagnum bogs during reproduction, but uses the forest habitat during the summer. It overwinters in terrestrial habitat, using old burrows or cavities created by rotting roots, below the freezing depth. It will frequently overwinter in groups, sometimes with other amphibians such as the red-backed salamander.[2][3][7]
In Canada, the four-toed salamander can be found in southern Ontario and Quebec, in Nova Scotia, and a single population was found in New Brunswick in 1983. In the United States, it can be found from Maine to Minnesota and as far as Alabama in the south. They have also been found in eastern Kentucky.[3][4][8][9][10][11]
The home range of the species is not known. It was believed that the different elements of its habitat (breeding, summer and overwintering) had to be within 100 m of each other, but recent observations might suggest this to be an underestimation.[2]
Four-toed salamanders feed mostly on small invertebrates, such as spiders, worms, ticks, springtails (collembola), ground beetles (Carabidae), and other insects. Larvae love small aquatic crustaceans.[2][3]
Larvae are eaten by other salamanders (adults and larvae), fish, and aquatic beetles. Shrews, snakes, and some ground beetles feast on this species. When it feels threatened, H. scutatum will use autotomy (drops its tail, still wiggling) to distract the attention of predators.[2][3]
Although it is rare, or at least rarely seen in Canada, Committee on the Status of Endangered Wildlife in Canada (COSEWIC) does not consider H. scutatum to be at risk.[12] It is also listed as a species of least concern by the International Union for Conversation of Nature (IUCN) due to the wide distribution and assumed large population.[13] But it is at risk in some provinces such as in Quebec (S3 Rare in the province; usually between 20 and 100 occurrences in the province; may have fewer occurrences, but with a large number of individuals in some populations; may be susceptible to large-scale disturbances).[14] Its status in the United States ranges from Threatened (Illinois), to Endangered (Minnesota), to Special Concern (Wisconsin, Ohio, and Missouri).[15]
The four-toed salamander (Hemidactylium scutatum) is a lungless salamander native to eastern North America. It is the only species of the monotypic genus Hemidactylium.
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