The Shenandoah salamander (Plethodon shenandoah) is a small, terrestrial salamander found exclusively in Shenandoah National Park in Virginia. The Shenandoah salamander inhabits a very small range of land on just three mountain peaks. Due to the small habitat range, interspecies competition, and climate change, the population of the Shenandoah salamander is vulnerable to extinction. Mitigating human effects on the habitat of the species will be essential in attempting to preserve and grow the population.
Description The adult Shenandoah salamander is slender and moderate in size, with a total length of 3.5 to 4.5 inches (7 cm - 10 cm).U.S. Fish and Wildlife Service. 1994. Shenandoah salamander (Plethodori shenandoah) Recovery Plan. Hadley, Massachusetts. 36 pp. The species has two distinct color phases: striped and unstriped. The striped color phase has a narrow stripe down the center of its back that can range in color from red to yellow, while the unstriped color phase is uniformly dark with occasional scattered brass-colored flecks. In both color phases, white or yellow spots occur along the sides of the body. The Shenandoah salamander is similar in appearance to the red-backed salamander (Plethodon cinereus). However, the two species can be distinguished in many ways. The stripe on the Shenandoah salamander takes up one-third of its dorsal area, while the stripe on the red-backed salamander is wider and takes up approximately two-thirds of the dorsal area. In addition, the Shenandoah salamander lacks the "salt and pepper" color pattern on its underside that is characteristic of P. cinereus, and has a slightly larger and more broadly rounded head. Shenandoah salamanders are members of the family Plethondontidae, the lungless salamanders that breathe through the surface of their skin. Due to the lack of lungs, successful respiration depends on the ability to maintain skin moisture, thus restricting body size and necessitating a moist environment such as forested areas. This species is chiefly nocturnal, hunting for food at night and taking cover in dark, damp locations like rock crevices and underneath logs during the day.
Life history Like most woodland salamanders, the Shenandoah salamander eats mites, flies, small beetles, springtails, and other soil invertebrates.T. K. Pauley 1980. The ecological status of the Cheat Mountain Salamander. United States Department of Agriculture. Forest Service, Elkins, WV. Report 7798. 160. Pp. No direct observation of predation of the Shenandoah salamander has ever been reported, but potential predators residing within the habitat of the Shenandoah salamander include ring-necked snakes, short-tailed shrews, brown thrashers, and towhees. The Shenandoah salamander's life history is not well understood, though adult salamanders have a high survival rate, some even reaching 25 years of age. Like many salamanders, the breeding season for the Shenandoah salamander occurs during late spring or summer. Female salamanders do not breed prior to 4 years of age and lay an average clutch size of 13 eggs every other year. Clutches are laid in areas of moisture and incubate for 1–3 months. Fertilization occurs internally and the entire developmental process takes place within the egg—there is no aquatic larval stage. For the duration of the incubation period, females guard the nest and do not forage.
All salamanders, including the Shenandoah salamander, have an important impact on ecosystem functions. Salamanders regulate population dynamics via predation of insects and other invertebrates, aerate the soil through burrowing behavior, and influence large-scale processes such as decomposition.
Distribution
Habitat range The Shenandoah salamander species is believed to have originated in the Appalachians of eastern North America, though the historical abundance of this species is unknown. Currently, Shenandoah salamanders are exclusively found on the north-facing talus slopes of three mountains within the Shenandoah National Park in Virginia: Hawksbill, The Pinnacles, and Stony Man (see range map). Each of the three talus slopes houses an isolated salamander population residing at approximately 3,000 feet above sea level. The talus slopes are typically dry, so the Shenandoah salamander is generally found within moist microhabitats scattered throughout the talus environment. Although the dry talus slopes are not optimal, the Shenandoah salamander is excluded from optimal forested areas containing deep, moist soil due to competition with the red-backed salamander.
Population size Based on data from 2008/2009 there was a population estimate between 110,262 and 140,625, but current population trends and estimates cannot be established until surveys with marked animals are conducted.U. S. Fish and Wildlife Service (2012). Programmatic Biological Opinion for Shenandoah National Park Ongoing Management Activities.
Major threats
Red-backed salamander The Shenandoah salamander species is threatened by competition by the aggressive red-backed salamander, which restricts the Shenandoah salamander to dry, sub-optimal talus environments and prevents Shenandoah salamander populations from expanding into heavily forested areas. Furthermore, the talus habitat of the Shenandoah salamander is in a state of disintegration due to erosion. Eventually, this weathering will result in soil formation and a subsequent increase in moisture, thus making the talus environment suitable for red-backed salamander invasion and increasing the possibility of extinction of the Shenandoah salamander species
Both laboratory and field experiments have provided evidence of the red-backed salamander's aggressive, territorial behavior toward the Shenandoah salamander. The two species compete for large cover objects that provide cool temperatures and high moisture levels, but the territoriality of P. cinereus results in competitive exclusion of the Shenandoah salamander from moist soil environments. As a result, the Shenandoah salamander, which has a higher tolerance for dry conditions, is restricted to the talus slope environments in which the red-backed salamander cannot survive.
Invasive species Invasive insect species in the Shenandoah National Park, namely the gypsy moth (Lymantria dispar dispar) and the hemlock woolly adelgid (Adelges tsugae), also threaten the survival of the Shenandoah salamander. Gypsy moth larvae feed on tree leaves, resulting in widespread defoliation and tree mortality. This loss of overstory dramatically alters the Shenandoah salamander habitat, reducing the ground moisture and potentially altering the Shenandoah salamander's ability to catch prey. Hemlock woolly adelgids are a major cause of hemlock tree mortality within Shenandoah National Park, contributing to overstory loss and talus slope habitat dehydration. In addition, hemlock mortality increases the amount of hemlock needles in the soil, which lowers the pH of the soil. Acid deposition due to acid rain and/or air pollution also contributes to soil acidification and has been well-documented in Shenandoah National Park. Although the direct effects of soil acidification on the Shenandoah salamander have not been documented, studies have shown that amphibians are extremely vulnerable to this process.Corn, P. S., Stolzenburg, W., & Bury, R. B. (1989). Acid precipitation studies in Colorado and Wyoming: interim report of surveys of montane amphibians and water chemistry. Washington, DC: U.S. Dept. of the Interior, Fish and Wildlife Service, Research and Development. These results suggest that soil acidification within the Shenandoah salamander habitat could reduce reproduction, affect food supply, lower egg hatchability, and increase newborn salamander mortality.
Chytrid fungus Batrachochytrium salamandrivorans or salamander chytrid fungus causes the infectious disease chytridiomycosis, which is considered to be a large factor in the declining populations of amphibians globally.Martel, An, et al. "Batrachochytrium Salamandrivorans Sp. Nov. Causes Lethal Chytridiomycosis in Amphibians." Proceedings of the National Academy of Sciences of the United States of America, vol. 110, no. 38, 2013, pp. 15325–15329. JSTOR, www.jstor.org/stable/42713321. Accessed 2 Apr. 2020. In 2016, an interim rule by the U.S. Fish and Wildlife Service (USFWS) added all species of salamander to the list of injurious amphibians. This rule prevented the importation or transportation of any live of dead specimens, including parts, of the 20 genera of salamanders into the United States and interstate transportation between States, the District of Columbia, the Commonwealth of Puerto Rico, or any territory or possession of the United States.Injurious Wildlife Species; Listing Salamanders Due to Risk of Salamander Chytrid Fungus. (2016, January 13). Retrieved from https://www.federalregister.gov/d/2016-00452 Only with the exception of permit for zoological, educational, medical, or scientific purposes or by Federal agencies without a permit solely for their own use. This interim rule was a proactive rule to protect the wildlife from the introduction, establishment, and spread of Batrachochytrium salamandrivorans. While this fungus had a lethal effect on many salamander species, it was not currently known to be found in the United States; however, the potential introduction of the fungus upon the salamander species could have an incredibly devastating effect.
Anthropogenic factors Anthropogenic factors also appear to potentially further endanger the Shenandoah salamander. In the 1994 recovery plan, it was thought that further debilitation of overstory vegetation, changes in soil chemistry, and direct impacts to the salamanders associated with acid deposition and other sources of air pollution were potential threats. While there were no effects of acid deposition and other sources of air pollution on the Shenandoah salamander, there have been numerous studies which indicate amphibians to be very vulnerable to effects of acid deposition, especially in montane areas. Acidification of the habitat could affect the salamander's food supply, could impair reproduction by affecting courtship, egg hatchability, or neonatal viability. Studies showed that soil acidity decreased the abundance of the red-backed salamander, making it likely for the Shenandoah salamander to also be negatively affected. Finally, there was the potential disturbance to the habitat of the Shenandoah salamander due to hiking trail maintenance, use, and backcountry camping.
Climate change Climate change also directly impacts the habitat of the Shenandoah salamander. Cloud base elevation, which is influenced by climate variables, is likely to continue to shrink the suitable range of the Shenandoah salamander.Grant, Evan H. Campbell, et al. "Evidence That Climate Sets the Lower Elevation Range Limit in a High‐Elevation Endemic Salamander." Ecology and Evolution, vol. 8, no. 15, 2018, pp. 7553–7562., One study found that elevation is strongly correlated with the lower elevation range boundary for the Shenandoah salamander, despite previous assumptions that the range was limited only to competitive interactions. The lower elevational range is sensitive to climate variables, so climate change in high elevation habitats will directly affect the species' distribution.
Conservation status In December 1982, the U.S. Fish and Wildlife Service categorized the Shenandoah salamander as a "Category 2" in its Review of Vertebrate Wildlife for Listing as Endangered or Threatened Species.U. S. Fish and Wildlife Service (1982). Endangered and Threatened Wildlife and Plants; Review of Vertebrate Wildlife for Listing as Endangered or Threatened Species. Federal Register, 47(251), 58454-60. In 1989, the Shenandoah salamander was formally classified as "Endangered" under the Endangered Species Act (ESA).