Peaks of Otter Salamander
© 2011 Timothy Burkhardt (1 of 9)
Country distribution from AmphibiaWeb's database: United States
Plethodon hubrichti Thurow, 1957
Joseph C. Mitchell1
1. Historical versus Current Distribution. Peaks of Otter salamanders (Plethodon hubrichti) are endemic to the Blue Ridge Mountains, restricted to an approximately 16-km length of the mountain chain in Bedford and Botetourt counties, Virginia (Highton, 1972, 1986d; Mitchell and Reay, 1999). Information on their historical range is not available.
2. Historical versus Current Abundance. Historical abundance is unknown, but was probably less than today because of agricultural practices in the area in the 1800s and early 1900s. In optimal areas, current abundance can be high. Current abundance is affected by timber operations in parts of its range in the Jefferson National Forest. Kramer et al. (1993) marked 250 Peaks of Otter salamanders in a 10 x 10 m plot and estimated a population size of 450 individuals. Average density/field trip was 0.24 individuals/m2. Mitchell and Wicknick (1996) found 0.13–0.18 salamanders/m2 in transects in mature forests, 0.5–0.16/m2 in forest stands that had been thinned, and 0.04–0.09/m2 in recent clearcuts.
3. Life History Features. The ecology and life history of Peaks of Otter salamanders has been summarized by Pague and Mitchell (1991b) and Petranka (1998); details are given below.
A. Breeding. Reproduction is terrestrial.
i. Breeding migrations. Peaks of Otter salamanders do not migrate to breeding locations.
ii. Breeding habitat. Breeding apparently occurs in and on leaf litter in hardwood forests and under logs and rocks in moist soil.
i. Egg deposition sites. Females lay eggs under logs and rocks in deep soil (Pague, 1989).
ii. Clutch sizes. Females lay 5–15 eggs (Pague, 1989).
C. Direct Development. Mating occurs in September and October when pairs of males and females may be found under the same log or rock (Wicknick, 1995). Females lay eggs in June (Pague, 1989). Hatching occurs in August and September. The few nests that have been observed were under rocks in moist soil. Females were in attendance on these nests (J.C.M., unpublished data).
D. Juvenile Habitat. Juvenile habitat is similar to adult habitat.
E. Adult Habitat. Within the range of this species, adults occupy the forest floor of mature Appalachian hardwood forest at elevations ≥ 550 m above sea level (Pague and Mitchell, 1991b). Salamanders have been found in a variety of vegetation types, including rhododendron thickets. Rocks and logs are usually in abundance. Salamanders are not distributed evenly throughout their range, instead highest densities occur in areas of deep, moist soil in mature hardwood forest stands.
F. Home Range Size. Median area for home range of Peaks of Otter salamanders has been measured at 0.6 m2 in hardwood forest, and median distance moved was 1.0 m (Kramer et al., 1993).
G. Territories. Peaks of Otter salamanders are intraspecifically territorial. They exhibit most of the characteristics of a territorial salamander species (as defined by Gergits, 1982). They are site tenacious and can remain associated with a particular site (cover object: rock or log) within and between years (Wicknick, 1995). They may have the ability to home after displacement, although this is not yet clear (Wicknick, 1995). They are aggressive toward intruding conspecifics, retaining residency of an area and successfully expelling conspecific intruders (Wicknick, 1995). Negative intra-and intersex spatial associations indicate that intraspecific territoriality occurs within and between sexes (Wicknick, 1995). Competition for cover objects via intra- and interspecific territoriality has been only weakly supported by field experiments conducted in the fall (Wicknick, 1995).
H. Aestivation/Avoiding Dessication. Surface activity ceases when the forest floor is dry. This can occur for several days to weeks during the normal activity period (usually April to early November).
I. Seasonal Migrations. This species does not migrate.
J. Torpor (Hibernation). Peaks of Otter salamanders usually are inactive during November–March, although periods of warm temperatures and moist surface conditions may cause these salamanders to become active on the forest floor for short periods of time during these months. The coldest soil temperature for surface-active individuals we measured was 10.0 ˚C on 14 October 1994 (unpublished data). None were observed in the same sites at 9.0 ˚C.
K. Interspecific Associations/Exclusions. Peaks of Otter salamanders occur sympatrically with southern two-lined salamanders (Eurycea cirrigera), seal salamanders (Desmognathus monticola), spring salamanders (Gyrinophilus porphyriticus), eastern red-backed salamanders (Plethodon cinereus), white-spotted slimy salamanders (Plethodon cylindraceus), red salamanders (Pseudotriton ruber), and eastern newt (Notophthalmus viridescens) efts. Eastern red-backed salamanders, the sibling species of Peaks of Otter salamanders, occur in a highly variable zone of overlap but generally narrow band of sympatry around the margins of the range of the Peaks of Otter salamanders (Wicknick, 1995). Wicknick (1995) found some support for competition for cover objects and their associated resources between Peaks of Otter salamanders and eastern red-backed salamanders. The two species occur in the same microhabitat but are negatively associated when in sympatry (Wicknick, 1995). It appears that Peaks of Otter salamanders hold interspecific territories, but despite a relatively high level of aggression, are only moderately successful at defending a site against invasion by red-backed salamanders (Wicknick, 1995). The two species may be in competitive equilibrium.
L. Age/Size at Reproductive Maturity. Age at maturity is unknown, but minimum size known for reproductive adults of both sexes is 39 mm SVL (Wicknick, 1995; Mitchell and Wicknick, 1996).
M. Longevity. Longevity is unknown.
N. Feeding Behavior. Peaks of Otter salamanders are opportunistic feeders along and above the forest floor on low herbaceous vegetation during warm, wet nights (Kramer et al., 1993). Prey include a wide variety of invertebrates, including ants, collembolans, isopods, beetles, spiders, centipedes, gastropods, worms, and lepidopteran larvae (Mitchell and Wicknick, 1996). Mitchell et al. (1996b) found 949 prey in 80 salamanders from 20 sites, of which 32.2% were ants and 67.8% were collembolans. They determined that there were no significant differences in numbers of ants consumed in four forest stand types (recent clearcut, old clearcut, mature, and shelterwood). However, salamanders in mature stands ate significantly more collembolans than those in other forest stand types.
O. Predators. Actual predation has not been observed. Sympatric snakes include ring-necked snakes (Diadophis punctatus), common garter snakes (Thamnophis sirtalis), juvenile black racers (Coluber constrictor), and milk snakes (Lampropeltis triangulum). Potential bird predators include wild turkeys (Meleagris gallopavo), towhees (Pipilo sp.), and brown thrashers (Toxostoma rufum) that forage in the leaf litter. Short-tailed shrews (Blarina brevicauda) and southeastern shrews (Sorex longirostris) occur sympatrically with Peaks of Otter salamanders.
P. Anti-Predator Mechanisms. Anti-predator behaviors include noxious skin secretions, immobility, and defensive postures (Brodie, 1977; Dodd et al., 1974). Dodd (1989) determined the length of time salamanders remained immobile when disturbed in the field by close approach, when their nearby microhabitat was disturbed, or when they were touched. Immobility times for Peaks of Otter salamanders averaged 16.3 s (range = 1.5–99.5 s) and were not significantly different from times for other eastern Plethodon. Three of 28 salamanders had immobility times > 180 s in duration.
Q. Diseases. Unknown.
R. Parasites. There are no published observations on parasites for this species.
4. Conservation. Peaks of Otter salamanders are recognized as a Federal species At Risk by the U.S. Fish and Wildlife Service and listed as a Species of Concern by the Virginia Department of Game and Inland Fisheries (Mitchell et al., 1999). The U.S. National Forest Service lists them as a Sensitive Species. Potential threats include logging activities, habitat fragmentation, and loss of forest canopy from the introduced gypsy moth (Lymantria dispar; Mitchell et al., 1996b; Sattler and Reichenbach, 1998). Mitchell et al. (1996b) determined that numbers of Peaks of Otter salamanders were highly variable and that clearcut sites consistently supported fewer individuals than mature forest or stands that had been thinned (shelterwood sites). This study also showed that diet quality may decrease following clearcutting. In another study, numbers of salamanders were stable over a 3-yr period in mature hardwood and shelterwood stands, but declined substantially after clearcutting (Sattler and Reichenbach, 1998). In the clearcut site, 30% of the initial population remained after treatment; many adults and juveniles either likely emigrated or died.
The current conservation plan followed by the U.S. Forest Service and the U.S. National Park Service (George Washington and Jefferson National Forests, U.S. Fish and Wildlife Service, and Blue Ridge Parkway, 1997) specifies the entire range of the Peaks of Otter salamander as a Special Biological Area with a primary conservation area that allows no logging activities and a secondary conservation area that allows logging to take place under certain restrictions. These restrictions include the use of the shelterwood technique only, a 50 ft2 basal area minimum, no cutting of remaining hardwood trees for 15 yr, location of the timber sale area away from previous sale areas, and seeding of the logged area with downed woody debris. In addition, cutting cannot occur during peak salamander surface activity time and no more than 100 ac may be harvested per year.
1Joseph C. Mitchell
2Jill A. Wicknick
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 20 Jun 2018.
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