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Plethodon wehrleiWehrle's Salamander

By Hannah Reed

Geographic Range

Wehrle's salamanders, Plethodon wehrlei, are distributed throughout the Nearctic region, mainly indigenous to the Appalachian Mountain Plateau. The northernmost region that these salamanders are found is southwestern New York. Their range continues southward into Pennsylvania, southeastern Ohio, West Virginia, southwestern Virginia, and northwestern North Carolina. An isolated population can be found along the border of southeastern Kentucky and northeastern Tennessee. (Mitchell and Gibbons, 2010; Petranka, 2010; Wilson, 1995)

Habitat

Within their range, these salamanders are commonly found on wooded hillsides of mountains with elevations above 183 m. Suitable habitats include, red spruce Picea rubens and yellow birch Betula alleghaniensis forests, mixed deciduous and coniferous forests with an abundance of coverage, such as rocks, logs, and leaves. The salamanders live among mature hardwood forests when inhabiting lower elevations. Compared to other salamander species, Wehrle's salamanders typically occupy drier habitats. Although they tolerate drier habitats better than most Plethodon salamanders, Wehrle’s salamanders are not immune to desiccation. When extremely dry conditions exist, these salamanders can burrow down into the soil, and even squeeze between narrow gaps between rocks. Tolerant of these rocky habitats, they can also inhabit cave entrances where light still penetrates. (Fergus and Hansen, 2003; Gibbs, et al., 2007; Mitchell and Gibbons, 2010; Petranka, 2010; Wilson, 1995)

  • Other Habitat Features
  • caves
  • Range elevation
    183 (low) m
    600.39 (low) ft

Physical Description

Wehrle's salamanders are considered to be a large, slender member of the Plethodon genus. They have a dark gray or brown body marked on the sides with an irregular row of white, bluish white, or yellow spots or dashes. These spots may be arranged in two rows that are yellow in color in some populations in Tennessee, Kentucky, and West Virginia. These yellow-spotted Wehrle's salamanders occur in isolated populations, and it's unknown if they are a distinct subspecies. Genetic analyses are in progress.

Salamanders inhabiting cave area may demonstrate variation of coloration and distribution of spots. For example, in Roanoke County, Virginia Wehrle’s salamanders living in the Dixie Caverns and Blankenship Cave typically have a purplish brown dorsum profusely frosted with small white flecks and bronzy molding. The dorsal spots of juveniles are often red and arranged in pairs. Adults usually have brassy dorsal flecks with little white dots. In the southern portions of their range, the middorsal area may lack conspicuous markings or have spots arranged in pairs that are yellow, red, or orange-red in color. With the exception of a white or white-blotched throat with frequent small spots extending to the chest, their venter is uniformly gray. Their forelimbs and hindlimbs are nearly equal in size. The webbing of their hindfeet extends to the tips of their first two toes. Typically, their tails are rounded and can grow up to the equivalence of their body length. The number of costal groves they have ranges from 16-18, but most individuals have 17.

Adult salamanders can range from 100-170 mm from head to tail (HT), or 50-75 mm snout-vent length (SVL). The majority of male salamanders’ sizes ranges from 100-160 mm HT, and 50-65 mm SVL, making them slightly smaller than females. Males also distinguish themselves from females by having cloacal papillae and enlarged mental glands. (Beane, et al., 2010; Gibbs, et al., 2007; Lannoo, 2005; Mitchell and Gibbons, 2010; Petranka, 2010; Powell, et al., 2016)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    100 to 170 mm
    3.94 to 6.69 in

Development

Little information specifically regarding the embryonic development of Wehrle's salamanders has been documented. Members of the Plethodon genus have an embryonic development span of approximately 72 days. Unlike most salamander species, Plethodon embryos lack metamorphic changes to the hyobranchial skeleton, a lateral line system, a fin fold on the tail, punitive Leydig cells on the integument, open gill clefts, and a larval dermal bone. The terrestrial larvae hatch from the egg capsules as miniaturized versions of mature adult salamanders. Plethodon larvae also lack a nasolabial groove, which is a diagnostic trait to the Plethodontidae family. They eventually develop this trait as they develop into adults. Plethodon larval direct development allows them to skip the intervening larval stage, making their cycle of metamorphosis incomplete. Hatchlings of members from the Plethodon genus are born with SVL measurements ranging from 12-20 mm and grow rapidly during their first year of life. Wehrle’s salamanders grow approximately 20 mm during their first year of life. Males increase their SVL length by 9-11 mm per year during their second, third, and fourth years of life. In contrast, females’ growth rate is slower during their second year of life with only a 5-7 mm increase in SVL. However, females grow an average of 9 mm annually until they reach sexual maturity. Wehrle’s salamanders are considered juveniles until their SVL reaches approximately 40 mm. At three years of age male Wehrle's salamanders begin to develop mental glands and cloacal papillae. They do not begin breeding until their fourth year. Female sexual maturity is indicated by enlargement of ovarian follicles. Females begin ovarian cycles at around five years of age. The growth rate for both sexes slows drastically after reaching sexual maturity. However, an increase of SVL length is still observed annually. (Altig and McDiarmid, 2015; Bonett and Blair, 2017; Hall and Stafford, 1972; Highton, et al., 2012; Kerney, 2011; Lannoo, 2005; Marvin, 1996; Petranka, 2010)

Reproduction

Wehrle's salamanders mate terrestrially. Monogamous mating occurs from March through October depending on the latitude of geographic range. Salamanders inhabiting northern regions, such as New York and Pennsylvania, typically mate in in late September through early October. Males begin to produce spermatophores in August. Female Wehrle’s salamanders lay their eggs during mid-winter through early spring, and the larvae begin to hatch in March. Mating usually happens during March and April for salamanders in West Virginia and Virginia. Unlike populations in the northern geographic range, males begin to produce spermatophores in October. Females will lay their eggs in May and June. The males breed annually, while females typically breed biennially. Male salamanders use pheromones to attract female salamanders. During courtship, the males’ mental glands secrete pheromones on their chins. The pheromones are used to enhance female responsiveness to the males. To administer the pheromone to the females, males wipe their mental glands across the females’ dorsum while scraping her skin with premaxillary teeth. Females may also receive the pheromones by the males slapping their mental glands directly onto their nares. The female will then pick up the sperm caps from spermatophores deposited on the ground, which fertilizes the eggs once they pass through the cloacal orifice. (Highton, et al., 2012; Lannoo, 2005; Mitchell and Gibbons, 2010; Palmer, et al., 2005; Petranka, 2010; Server, 2016; Wilson, 1995)

Male Wehrle's salamanders typically reach sexual maturity at three years of age. However, they do not begin breeding until the age of four. During mating season, males will evacuate their testes from their internal body. After mating occurs, the testes are then retracted back into the males’ bodies. Female salamanders reach sexual maturity at the age of five. Breeding occurs once annually for male salamanders and most females breed once every two years. Green and Pauley (1987) suggested that mature female salamanders oviposit in deep underground cavities. Only one nesting record has ever been found above ground, which was a clutch of six eggs in a Virginia cave. The eggs are unpigmented but appear as a creamy white color due to being surrounded by the vitelline membrane and two jelly enveloped. Adjoining eggs may be loosely fused together by tubular extensions of the outer envelope when they are laid in grape-like clusters. The average diameter of the outer capsule is 6 mm with the ova measuring 5 mm in diameter. Females will lay between 7-24 eggs; larger females tend to lay more eggs than smaller females. The number of eggs females will lay may also be inferred by the number of their enlarged ova. The length of incubation period for Wehrle’s salamander eggs is unknown. However, the average time from egg-laying until hatching for Plethodon species lasts 72 days. The female salamanders brood the eggs until they are hatched. Once the hatchlings emerge from the egg capsule, they are independent. (Green and Pauley, 1987; Hall and Stafford, 1972; Highton, et al., 2012; Kerney, 2011; Lannoo, 2005; Mitchell and Gibbons, 2010; Petranka, 2010; Wilson, 1995)

  • Breeding interval
    Male Wehrle's salamanders breed once yearly and females usually breed once every two years.
  • Breeding season
    Fertilization occurs in March through April or September through October, depending on geographical range. Females oviposit from March through June, depending on the geographic range.
  • Range number of offspring
    7 to 24
  • Range time to independence
    0 (low) days
  • Average age at sexual or reproductive maturity (female)
    5 years
  • Average age at sexual or reproductive maturity (male)
    3 years

During embryonic development, female Wehrle's salamanders will brood their egg clusters until the hatchlings emerge from their egg capsules. The male salamanders abort paternal care promptly after fertilization. (Highton, et al., 2012; Kerney, 2011; Lannoo, 2005; Mitchell and Gibbons, 2010; Wilson, 1995)

Lifespan/Longevity

The lifespan of Wehrle's salamanders is unknown. However, their close relatives, northern slimy salamanders, Plethodon glutinosus, are believed to live up to 20.1 years in captivity. Staub (2016) reported that members of the Plethodon genus can live up to 36 years in captivity. Longevity within natural habitats for Plethodon salamanders remains unknown. (Snider and Bowler, 1992; Staub, 2016)

Behavior

Wehrle's salamanders are primarily sedentary apart from occasionally moving vertically in the soil when surface conditions become too dry. They remain in the same area for their entire lives. Typically, they are solitary animals and do not interact with other salamanders outside of breeding season. From March through October they are active at night to forage for prey on the damp forest floor. In the summer months they remain underground during the day to avoid desiccation. Salamanders inhabiting higher elevations burrow underground for hibernation in late October. They do not emerge from hibernation until late April. Salamanders living in lower elevations burrow beneath the surface for hibernation in late September and do not emerge until March. When threatened, the salamanders will be immobile, avoiding detection. Dodd and Brodie (1976) revealed that Wehrle’s salamanders have the longest immobility duration within their genus. If these salamanders are detected by predators, they can produce odorous, noxious skin secretions that initiate indigestion in smaller predators, making them undesirable to consume. Another anti-predator defense includes tail-base constrictions, allowing the salamanders to detach their tail from their bodies; tails will regenerate completely over time. The detached tail often distracts predators and gives the salamanders time to escape. (Beneski, 1989; Dodd, 1989; Dodd and Brodie, 1976; Lannoo, 2005; Mitchell and Gibbons, 2010; O'Donnell and Semlitsch, 2015; Petranka, 2010)

Home Range

The home range of Wehrle's salamanders is unknown. However, it is assumed that they share a similar range with other large Plethodon species. The home range for eastern red-backed salamanders, Plethodon cinereus, is 13 m^2 for juvenile and males and 24 m^2 for females. Wehrle’s salamanders actively defend their territories from other Plethodon species, especially during mating season. They have been known to bite the tails off of smaller Plethodon species. (Lannoo, 2005; Mitchell and Gibbons, 2010; Petranka, 2010)

Communication and Perception

Male Wehrle’s salamanders use their mental gland to secrete substances onto their chins. The secretions are pheromones that are delivered to the female salamanders during courtship. In most Plethodon species, the females follow the males with her chin on his dorsal tail base during courtship. Once males deposit their spermatophore, they continue to lead the female until her cloacal orifice comes into contact with it. Other than to serve as a sexual attractant, the purpose of the pheromone is to increase mating success and female receptivity. These salamanders also rely on their visual senses to analyze their surrounding environments and to communicate with other salamanders. (Palmer, et al., 2005; Server, 2016)

Food Habits

Wehrle's salamanders nocturnally forage for their prey in low vegetation on the forest floors. However, they have been spotted exposed on the ground surface during the day during wet, foggy, and dark conditions. Occasionally, individuals have been found foraging on tree trunks, specifically in West Virginia. Optimal foraging typically occurs in warm, wet conditions. Their prey varies seasonally and ontogenetically. Generally smaller prey items including ants, springtails, mites, beetles, and spiders are the dietary mainstay of juvenile salamanders. Adult salamanders in Pennsylvania primarily consume European strawberry weevils, Otiorhynchus ovatus. Other adult salamanders mostly consume arthropods, such as beetles, springtails, millipedes, centipedes, orthopterans, crane flies, ants, homopterans, hemipterans, lepidopteran larvae, aphids, fresh water isopods, and weevils. Arachnid prey consists of mites, spiders, and phalangids. Their diets also include gastropods and annelids. During the summer months the majority of prey consumed by both juvenile and adult salamanders includes insect larvae, ants, crickets, spiders, weevils, and orthopterans. (Gibbs, et al., 2007; Lannoo, 2005; Mitchell and Gibbons, 2010; Petranka, 2010)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • other marine invertebrates

Predation

The only documented predator of Wehrle’s salamanders are northern ring-necked snakes (Diadophis punctatus edwardsii). However, other snakes, such as eastern garter snakes (Thamnophis sirtalis), ground-foraging birds, and shrews are also believed to prey on these salamanders. When threatened, the salamanders will be immobile, avoiding detection. Dodd and Brodie (1976) revealed that Wehrle’s salamanders have the longest immobility duration within their genus. If these salamanders are detected by predators, they can produce odorous, noxious skin secretions that initiate indigestion in smaller predators, making them undesirable to consume. Another anti-predator defense includes tail-base constrictions, allowing the salamanders to detach their tail from their bodies; tails will regenerate completely over time. The detached tail often distracts predators and gives the salamanders time to escape. (Beneski, 1989; Dodd, 1989; Dodd and Brodie, 1976; Lannoo, 2005; Mitchell and Gibbons, 2010; Petranka, 2010)

  • Known Predators
    • northern ring-necked snakes (Diadophis punctatus edwardsii)

Ecosystem Roles

Wehrele's salamanders are known to host the protozoan Batracholandros magnavulvaris. It is uncommon for these salamanders to be affected by this protozoan. Therefore, they do not have a large impact on their food web. Other members of the genus Plethodon have been known to harbor a protozoan ciliate, Cepedietta michiganesis. (McAllister and Bursey, 2004; McAllister, et al., 2013; Powders, 1970)

Commensal/Parasitic Species
  • Protozoans (Batracholandros magnavulvaris)

Economic Importance for Humans: Positive

Adult salamanders in Pennsylvania primarily consume European strawberry weevils, Otiorhynchus ovatus. These weevils are a nuisance species due to their detrimental effects of plants, specifically strawberry plants. By Wehrle's salamanders consuming them, humans are able to save money on pest management. (Mitchell and Gibbons, 2010; Pellitteri, 2007)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no negative impacts of Wehrle's salamanders on humans.

Conservation Status

Wehrle's salamanders are a species of "Least Concern" on the IUCN Red List. On the US Federal List, CITES, and the State of Michigan List, these salamanders hold no special conservation status. In many areas, they are considered to be the most abundant species within their habitat. However, in North Carolina they are listed as a state-threatened species because their range is restricted to just two northern counties in the state. The conservation status of isolated populations of the yellow-spotted morph Wehrle's salamanders in Kentucky, Tennessee, and West Virginia has yet to be assessed. It's unknown if they are a distinct subspecies. Genetic analyses are in progress, thus making it more critical to preserve the remaining population. Habitat loss due to timber harvesting, construction of roads and houses, mountain top removal, and hydraulic fracturing are threats to Wehrle's salamanders. No official conservation acts have been implemented to preserve Wehrle's salamander. However, the USDA recommended that landowners maintain montane oak, Quercus prinus, forests due to their association with Wehrle's salamander habitats. (Hall and Stafford, 1972; IUCN SSC Amphibian Specialist Group, 2014; Kiviat, 2013; Lannoo, 2005; Mitchell and Gibbons, 2010; "Nantahala and Pisgah National Forests plan revision draft", 2013; Petranka, 2010; Petty, et al., 2013)

Other Comments

Wehrle's salamanders were named by Fowler and Dunn of the Academy of Sciences after naturalist, R.W. Wehrle. He is credited with discovering the salamanders in the Two Licks Hills area of Indiana County, Pennsylvania in September 1911. (Buckles, 2013; Newman, 1954)

Contributors

Hannah Reed (author), Radford University, Layne DiBuono (editor), Radford University, Lindsey Lee (editor), Radford University, Kioshi Lettsome (editor), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

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