The Peaks of Otter salamander (Plethodon hubrichti) is a species of salamanders in the family Plethodontidae. It is endemic to the Peaks of Otter area in the Blue Ridge Mountains of Virginia. It is a montane salamander found at elevations above , but more commonly above . It can be locally common, but its distribution is small and patchy. This makes it vulnerable to local threats such as timber harvesting, recreational development, defoliation by gypsy moths, and spraying to control the latter.
Description The adult Peaks of Otter salamander is characterized by a dark-brown dorsum with heavy brassy flecking down its entire length. The dorsum and sides of P. hubrichti may also be lightly speckled with white, while the venter is not spotted and ranges from light to charcoal grey in color. Males have small mental glands immediately behind the chin.Petranka, J. 1998. Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C., 583 pp. While the Peaks of Otter salamander is superficially similar to the Cheat Mountain salamander (P. nettingi), the two species are differentiated by a higher concentration of metallic flecking on the dorsum of P. hubrichti, and the presence of a usual 19 costal grooves compared to the variable 17–19 costal grooves of P. nettingi. Although Petranka stated that hatchlings have a distinct dorsal stripe consisting of reddish spots, this was never seen in over 100 neonates observed, which have a uniform dark-grey dorsum. Brassy flecks begin to appear when salamanders reach about 25 mm snout-to-vent length.Kniowski, A., and N. Reichenbach. 2006. Plethodon hubrichti (Peaks of Otter salamander). Reproduction. Herpetological Review 37: 332.
In the early 1950s, the P. cinereus group of small Plethodon species was made up of only three species: the southern ravine salamander (P. richmondi), the Cheat Mountain salamander (P. nettingi), and the eastern red-backed salamander (P. cinereus). Numerous other members of the genus have since been described, including the Peaks of Otter salamander.
Naming The story of P. hubrichti'''s naming began in 1949 with a typewriter salesman, Leslie Hubricht, who also collected and studied land snails. Hubricht encountered salamanders in his pursuit of snails because of their similar habitats, and sent any unusual salamanders he found to museums for identification. Some salamanders he had collected in the Blue Ridge Mountains of Virginia were identified as P. nettingi by herpetologist Gordon Thurow. If true, this would have represented a significant range extension for P. nettingi, since this species had been known only from West Virginia. Richard Hoffman and Richard Highton also examined these specimens, and suspected they actually represented a new species or subspecies.Highton, R. 2009. The Discovery of Plethodon hoffmani and Plethodon hubrichti and Why Richard L. Hoffman Became a Myriapodologist. Pp. 55-57, in S.M. Roble and J.C. Mitchell (eds.). 2009. A Lifetime of Contributions to Myriapodology and the Natural History of Virginia: A Festschrift in Honor of Richard L. Hoffman's 80th Birthday. Virginia Museum of Natural History Special Publication No. 16, Martinsville, VA.
Hoffman and Highton successfully located Hubricht's collection site about 0.9 miles south of the Black Rock Hill Overlook on the Blue Ridge Parkway, and after collecting and examining 24 of their own specimens, confirmed their suspicions that this was a new species. The two prepared a manuscript describing the salamander, which they designated P. aureolus, and planned to submit the account for publication by December 1956. However, P. aureolus was never to officially exist as the scientific name for the salamander discovered by Leslie Hubricht in the Blue Ridge Mountains. Shortly before Hoffman and Highton's manuscript was submitted, Highton phoned Gordon Thurow, who was in the army at the time, and was stationed near where he lived. Richard invited Gordon and his wife over for dinner at their home. During the phone conversation, Richard told Gordon that he had found Leslie Hubricht's site along the Blue Ridge Parkway and that Gordon had misidentified the specimens Hubricht collected as P. nettingi. Richard also told Gordon that the specimens were of a new species and that he and Richard Hoffman were in the process of describing it. When Gordon and his wife came over for dinner, Richard showed Gordon the new specimens Hoffman and he had collected. During the visit, Gordon never mentioned that right after he received the phone call from Richard Highton, he rushed to Hubricht's collection site and collected some specimens for himself. He then swiftly submitted his own description of this new species,Thurow, G. 1957. A new Plethodon from Virginia. Herpetologica. 13: 59-66. giving the Peaks of Otter salamander its official specific epithet of hubrichti. This less-than-honorable rush to be the first to name this new species, plus other similar events, caused Richard Hoffman, a budding Virginian herpetologist at the time, to look for another group of animals in the forests of Virginia that needed taxonomic work. He decided to work with millipedes.
Distribution The Peaks of Otter salamander is endemic to a 19-km stretch along the Blue Ridge Parkway in the Peaks of Otter area of the Blue Ridge Mountains in Bedford, Botetourt, and Rockbridge Counties of west-central Virginia. P. hubrichti occupies forest floor habitats and is generally found at elevations above 845 m.
Distribution in allopatry When not in sympatry with the Eastern Red-backed salamander (P. cinerus), P. hubrichti surface-active salamander densities decreased with elevation. Reichenbach and Brophy performed a study between 2008 and 2010 on allopatric populations of P. hubrichti at elevations ranging from 488 to 1143 m. They measured eggs/female, % gravid females, surface-active salamander density, temperature and relative humidity. Surface-active salamander densities, survival rates, growth rates, eggs/female and reproductive output decreased with elevation. Decreases were related to increases in temperature and a decrease in relative humidity associated with decline in elevation. Being a montane species, P. hubrichti is affected by even slight changes in the aforementioned environmental factors. This sensitivity to changes in their habitat restricts them from inhabiting lower elevations, where their range may be abiotially limited by the warmer temperatures and drier conditions.
Understanding the reasons why the Peaks of Otter salamander has such a restricted distribution can contribute greatly to its conservation. Previous work has shown that, at optimal elevations in the core of its range, P. hubrichti dominates the salamander community and can be found at high population densities (Reichenbach & Sattler, 2007). At the optimal elevation, when shelterwood cuts were conducted (partial removal of trees), the Peaks of Otter salamander densities did not decline following timbering. If these same shelterwood cuts had been conducted in lower elevation areas, however, the already sparse populations of P. hubrichti might have been adversely affected since the forest canopy would have been opened, likely resulting in increased temperatures and decreased RH. These increased temperatures and decreased RH might exceed or be closer to the tolerable limits for P. hubrichti, which could either extirpate them from these low elevations or reduce densities. Therefore, it is important to conserve mature hardwood forests, particularly in lower elevation areas in the perimeter of the Peaks of Otter salamander distribution, which represent more fragile salamander habitats.
Reproduction The first observations of a P. hubrichti nest were made in spring and summer of 2005, at a study site near Onion Mountain in Bedford County A cluster of about 10, 5.5-mm-diameter eggs, attended by the brooding female, was found beneath a rock embedded in the soil, hanging from the soil chamber ceiling. After 42–48 days of development, motile embryos with visible eyes were observed in the eggs, and 16 days later, hatchlings were found at the nest site.
The number of eggs per female ranged from 1 to 12 with a mean of 8.5 (95% CI 8.2–8.9). The number of eggs per female P. hubrichti increased directly with mass and elevation to a maximum of 12 eggs per female at 1000 m and then decreased slightly above 1000 m. While females found at higher elevations, near optimal elevations, typically produced more eggs per individual there was a greater percentage of females gravid at lower elevations. Combining data on salamander densities, number of eggs per female, and % gravid females (percentage of females in a population that are carrying eggs) allowed for the calculation of reproductive output for populations of salamanders at various elevations. While females at lower elevations reproduced more frequently than females nearer optimal elevations, the pattern for reproductive output was similar to that seen in eggs per female with reproductive output increasing from low elevations to a maximum near 900 m and then declining beyond that elevation.
Population ecology In comparison to many other terrestrial plethodontids, the Peaks of Otter salamander has a uniquely small distribution, but it may be locally abundant within its range.Kramer, P., N. Reichenbach, M. Hayslett and P. Sattler. 1993. Population dynamics and conservation of the Peaks of Otter salamander, Plethodon hubrichti. Journal of Herpetology 27: 431-435. The extremely limited range of the species and its narrow environmental requirementsArif, S., D. Adams, and J. Wicknick. 2007. Bioclimatic modeling, morphology, and behavior reveal alternative mechanisms regulating the distributions of two parapatric salamander species. Evolutionary Ecology Research 9: 843-854. put P. hubrichti in a tenuous position - easily threatened by forest disruption. The Peaks of Otter salamander is not distributed evenly within its range, and normal movements of individuals are restricted to approximately 1 m; therefore, any habitat alteration could fragment the population and affect the species' long-term survival. P. hubrichti is estimated to have a population density of 450 salamanders/100 m2, with a median individual home range of 0.6 m2, determined by mark/recapture studies.
Adults and juveniles reside mostly under cover objects, such as rocks and logs, and they are actively territorial in defending these against conspecifics. Neonates and young-of-the-year (YOY) are more likely to be found in the leaf litter.Kniowski, A., and N. Reichenbach. 2009. The Ecology of the Peaks of Otter Salamander (Plethodon hubrichti) in sympatry with the Eastern Red-backed Salamander (Plethodon cinereus). Herpetological Conservation and Biology 4: 285-294. Growth rates for various size classes have been estimated, as well. The YOY salamanders were observed to have a growth rate of 0.10 mm/day, while salamanders initially between 31 and 40 mm SVL had a rate of 0.09 mm/day, and those originally between 41 and 50 mm were observed to grow 0.08 mm/day.
The Peaks of Otter salamander is primarily active at night, between 8:00 and midnight (9–11 pm in spring, 10–12 pm in summer, and 8–11 pm in autumn). Surface-active individuals are most commonly associated with vegetation, when available, and with leaf litter damp from recent rainfall. The proportion of the population active at the surface immediately following a rainfall increases linearly with length of time between rainfall events. Plethodon salamanders feed on invertebrate prey more likely to be found at the surface, but require moist conditions for cutaneous respiration, causing them to retreat underground when surface moisture is lacking. With longer periods of time between rainfalls, salamanders presumably have less access to food and therefore a larger proportion of the population may be observed foraging at the surface after rain.