Larch Mountain salamander
© 1998 Henk Wallays (1 of 16)
Plethodon larselli Burns, 1954
Robert E. Herrington1
1. Historical versus Current Distribution. Larch Mountain salamanders (Plethodon larselli) were originally described as a subspecies of Van Dyke's salamanders (P. vandykei; Burns, 1954) and later elevated to full species status (Burns, 1962). They are endemic to a narrow region where the Cascade Mountains have been eroded by the Columbia River in the Columbia River Gorge. Nussbaum et al. (1983) indicated they had been reported from three counties (one in Washington and two in Oregon). Fieldwork conducted from 1981–'84 (Herrington, 1985) revealed several new populations and expanded the Washington range eastward into Klickitat County. Aubry et al. (1987) extended the range northward into Lewis County, Washington. While the historical distribution is unknown, it is likely that road building, forestry practices, and human population growth in the limited range of this species has resulted in the loss of some populations. Because of the continued interest in this species by the Washington Department of Wildlife (1993), their distribution is better known in Washington. Intensive fieldwork in Oregon could yield additional populations.
2. Historical versus Current Abundance. Little is known about the historical or current abundance of Larch Mountain salamanders, and there are no detailed population studies available. It has been reported that Larch Mountain salamanders exhibit a remarkably low level of genetic diversity (Howard et al., 1983). Currently, Larch Mountain salamanders are known from isolated patches of talus habitat (with some exceptions) that appear to be separated by large expanses of unsuitable habitat. Many localities with what appears to be suitable habitat do not contain this species. In optimal habitat, during ideal environmental conditions, Larch Mountain salamanders are relatively common. They are usually less abundant than sympatric western red-backed salamanders (P. vehiculum; in Washington) or Dunn's salamanders (P. dunni; in Oregon). However, searches conducted a few meters to either side of optimal habitat or during adverse weather conditions will often fail to detect them. Environmental alteration, such as clearcutting of trees on talus slopes, render the habitat unsuitable for Larch Mountain salamanders, while sustaining populations of more tolerant western red‑backed salamanders (Herrington, 1985). During June 1998, I revisited most of the known collection sites in both Washington and Oregon (Herrington, 1985); generally, where habitat is intact, I found Larch Mountain salamanders present. However, several sites had been severely impacted over the ensuing 13 yr by anthropogenic factors. In particular, clearcutting above one site (Mabee Mines) resulted in the erosional deposition of large amounts of soil over the exposed talus. This allowed the encroachment of hardwoods that have completely closed the canopy and greatly reduced the abundance of Larch Mountain salamanders. Also, along the Washougal River, private home developments have compromised several sites. Major road construction is planned for Oregon, which could jeopardize populations in that state.
3. Life History Features.
A. Breeding. Reproduction is terrestrial.
i. Breeding migrations. No breeding migrations are known.
ii. Breeding habitat. Courtship occurs on moist talus during suitable periods of temperature and moisture from September–April (Herrington and Larsen, 1987).
i. Egg deposition sites. Oviposition sites have not been located, but it is likely that gravid females descend to suitable moist chambers within the talus to oviposit and brood eggs.
ii. Clutch size. Egg numbers average 7.3 (range = 2–12, n = 43; Herrington and Larsen, 1987).
C. Direct Development. Although development has not been observed in either the field or laboratory, it is probable that young are produced directly from eggs deposited in talus slopes (Herrington, 1985). Hatchlings (18–21 mm SVL) appear in talus during the beginning of the fall rainy season (October–November), and the absence of yolk in these individuals suggest that hatching had occurred weeks earlier.
D. Juvenile Habitat. Juvenile habitat is probably similar to that of adults. Juveniles are collected along with adults from the same habitats.
E. Adult Habitat. Larch Mountain salamanders typically are associated with steep, at least partially forested, talus slopes. Within the slopes, rock size, nutrient import, and moisture levels interact to produce optimal habitat (Herrington and Larsen, 1985). Larch Mountain salamanders are not tolerant of completely open canopies, such as that which occurs following clearcutting, although such areas frequently contain the more tolerant western red-backed salamanders (Herrington, 1985; Petranka, 1998). Larch Mountain salamanders occasionally have been found in other habitats such as at the entrance to an ice cave (Aubry et al., 1987) and in forested situations apparently no longer associated with exposed talus (Jones and Bury, 1983). However, it appears that in the latter case, these probably represent old talus slopes that have undergone successional processes associated with increased soil accumulation and subsequent tree growth.
F. Home Range Size. The home range is unknown.
G. Territories. Territoriality has not been studied in this species, but see "Interspecific Interactions" below.
H. Aestivation/Avoiding Dessication. Highly seasonal precipitation patterns occur in the Pacific Northwest, with most rainfall occurring from October–March. Greatly reduced rainfall from May–September effectively reduces surface activity by Larch Mountain salamanders to periods immediately following substantial rainfalls. During dry periods, salamanders descend deeper in the talus to locate microhabitats with suitable moisture levels.
I. Seasonal Migrations. Migrations are unknown for this species.
J. Torpor (Hibernation). Salamanders are absent from the surface during snow cover, when temperatures are < 4 ˚C, or when conditions are dry. They presumably descend into the talus to where more favorable microclimates occur.
K. Interspecific Associations/Exclusions. The distribution pattern of members of the genus Plethodon within the range of Larch Mountain salamanders suggests that interspecific competition may play a role in the micro-geographic distribution of these species. Larch Mountain salamanders are sympatric with western red-backed salamanders throughout most of their range in Washington, and with Dunn's salamanders throughout their range in Oregon (Nussbaum et al., 1983). However, even though Dunn's salamanders occur only a few miles west of the westernmost Larch Mountain salamander population in Washington, and western red-backed salamanders occur west of the westernmost population of Larch Mountain salamanders in Oregon, I have been unable to find any locality, in either state, where all three species are sympatric.
L. Age/Size at Reproductive Maturity. Based on a relatively large sample of size distributions, it appears that male Larch Mountain salamanders attain sexual maturity at 39–42 mm SVL and at 3.0–3.5 yr old. Female Larch Mountain salamanders are ≥ 44 mm SVL and are at least 4 yr old. Clutch size determined from ovarian/oviductal eggs ranged from 2–12 (mean = 7.3), and oviposition probably occurs only every other year after sexual maturity is reached. This is the only known species of salamander that lacks abdominal fat bodies, and excess energy is stored in the tail.
M. Longevity. Nothing is known about the longevity of this species in the wild.
N. Feeding Behavior. Larch Mountain salamanders feed on a variety of small invertebrates, with mites and collembolans making up a large part of their diet (Altig and Brodie, 1971). They are capable of feeding below the surface of the talus in laboratory experiments (Smith and Herrington, 1989).
O. Predators. I am unaware of studies on predation of this species. However, large salamanders, such as Dunn's salamanders (Plethodon dunni) and Pacific giant salamanders (Dicamptodon sp.), are known to feed on other salamanders. Garter snakes (Thamnophis sp.) are often abundant in the same habitat as Larch Mountain salamanders and are known to feed on a variety of amphibians.
P. Anti‑Predator Mechanisms. Larch Mountain salamanders occasionally will coil, spring, and then lie motionless with their reddish venter exposed.
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. Larch Mountain salamanders are known from isolated patches of talus habitat that appear to be separated by expanses of unsuitable habitat. Because of the continued interest in this species by the Washington Department of Wildlife (1993), their distribution is better known in Washington. Localities with what appears to be suitable habitat do not contain these salamanders. In optimal habitat, this species is relatively common. Little is known about the historical or current abundance of Larch Mountain salamanders, and there are no detailed population studies available. Clearcutting above one site (Mabee Mines) resulted in the erosional deposition of large amounts of soil over the exposed talus. This allowed the encroachment of hardwoods that have completely closed the canopy and greatly reduced the abundance of Larch Mountain salamanders. Along the Washougal River, private home developments have compromised several sites. Major road construction is planned for Oregon, which could jeopardize populations in that state.
1Robert E. Herrington
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 15 Dec 2018.
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