Western Red-backed Salamander, Western Redback Salamander
© 2001 Henk Wallays (1 of 28)
Plethodon vehiculum (Cooper, 1860)
R. Bruce Bury1
1. Historical versus Current Distribution. Western red-backed salamanders (Plethodon vehiculum) range throughout much of western Washington and Oregon, and northward to southern British Columbia and Vancouver Island. They occur on some coastal islands eastward to an altitude of about 800 m in the Washington Cascades (Brown and Slater, 1939; Slater and Brown, 1941; Slater, 1955). According to Storm and Brodie (1970b), the easternmost record in the Columbia Gorge is about 5 km east of Stevenson, Skamania County, Washington. In Oregon, except for a record near Boring, southeast of Portland, western red-backed salamanders appear to be absent from the northern portion of the Oregon Cascades. South of Oakridge, Lane County, salamanders again occur in the Cascades, but only to the North Umpqua River in Douglas County (Storm and Brodie, 1970b). At this location, western red-backed salamanders occur at about 1,250 m, one of the highest known elevations for any western Plethodon (Storm and Brodie, 1970b).
2. Historical versus Current Abundance. Western red-backed salamanders are common in Douglas fir and other mixed forests throughout their range (Bishop, 1943; Nussbaum et al., 1983). Western red-backed salamanders are one of the few species of Pacific Northwest salamanders that are common in young forests (Corn and Bury, 1991; Petranka, 1998). They occur across all forest stand ages (Aubry et al., 1988; Aubry and Hall, 1991).
3. Life History Features.
A. Breeding. Reproduction is terrestrial. The mating season varies from November to early March, depending on geography. In Oregon, breeding activity may begin as early as September but peaks from November–January (Dumas, 1956; Peacock and Nussbaum, 1973). Females in many populations have biennial reproductive cycles (Peacock and Nussbaum, 1973; Petranka, 1998). They may only oviposit every third year on Vancouver Island (Ovaska and Gregory, 1989).
i. Breeding migrations. Do not occur.
ii. Breeding habitat. Same as adult habitat.
i. Egg deposition sites. Nests have rarely been found, suggesting that females lay eggs in subsurface retreats.
ii. Clutch size. Eggs number from 4–19 (mean usually near 10) and are large at 4.4–6.0 mm in diameter (Carl, 1943; Stebbins, 1951; Peacock and Nussbaum, 1973; Hanlin et al., 1979; Nussbaum et al., 1983; Norman and Swartwood, 1991).
C. Direct Development.
i. Brood sites. Females oviposit during the spring or early summer but nests have rarely been found, suggesting that females lay eggs in subsurface retreats. Eggs are laid in grape-like clusters attached to the roofs and sides of cavities under or in rocks and logs (Peacock and Nussbaum, 1973; Hanlin et al., 1979; Norman and Swartwood, 1991).
ii. Parental care. Females brood; on rare occasions males are found with brooding females (Norman and Smartwood, 1991).
D. Juvenile Habitat. Hatching occurs at about 13–15 mm SVL (Peacock and Nussbaum, 1973; Petranka, 1998). Hatchlings can be abundant on the forest floor in late autumn and early winter. Juveniles grow about 10 mm SVL annually for their first 3 yr. Microhabitat use varies with age (increased size). Juveniles (< 30 mm SVL) tend to use smaller cover objects such as leaf litter and stones, while larger animals use larger objects. During drier conditions, juveniles tend to be more active on the forest floor than are adults (Ovaska and Gregory, 1989).
E. Adult Habitat. Western red-backed salamanders are found beneath logs, bark, stones, and moss in cool, shaded areas (Dumas, 1956; Brodie, 1970; Nussbaum et al., 1983; Corn and Bury, 1991). They are sometimes extremely abundant in rocky, talus slopes. Bishop (1943) reports collecting many specimens from such areas and among loose stones at the foot of a cliff. Populations are found associated with rocky seeps, springs, and small streams in the northern Puget Trough and Cascade Range foothills in Washington (Leonard, 1996; Petranka, 1998).
F. Home Range Size. According to Ovaska (1988b), individuals show a high degree of site specificity, with adults maintaining small home ranges on the order of a few m2.
G. Territories. According to Ovaska (1987), adults and particularly males competing for females are aggressive during their mating season. Individuals can detect chemical odors from the fecal pellets and bodies of conspecifics. Both males and females avoid odors of conspecific males, but not females (Ovaska, 1988a). Nevertheless, adults frequently share cover objects, are rarely aggressive toward each other, and do not avoid burrows with fecal pellets, suggesting that while males may compete for females, they are not territorial (Ovaska, 1987, 1988a,b, Ovaska and Davis, 1992).
H. Aestivation/Avoiding Dessication. During the drier summer, adults retreat to moist underground sites, although juveniles remain active on the forest floor (Ovaska and Gregory, 1989).
I. Seasonal Migrations. Unlikely.
J. Torpor (Hibernation). During the winter, western red-backed salamanders move deep into the talus (Dumas, 1956; see also Petranka, 1998).
K. Interspecific Associations/Exclusions. Western red-backed salamanders are rarely found with Dunn's salamanders (Plethodon dunni) and species of torrent salamanders (Rhyacotriton sp.), which are species that inhabit wet areas such as seeps or sides of streams. Recently, I found western red-backed salamanders for the first time in sympatry with Del Norte salamanders (P. elongatus). The locality was in the West Fork of Cow Creek, a tributary of the South Fork of the Umpqua River, southwest of Roseburg, Douglas County, Oregon (personal observations). This area is in the Oregon Coast Range. I captured both species, and a few Dunn's salamanders, in a rocky talus slope, 5–20 m from a small, north-flowing creek.
L. Age/Size at Reproductive Maturity. Individuals become sexually mature between their second and third year, when males reach about 42 mm SVL and females reach about 44 mm SVL, although this varies geographically (Brodie, 1970). The largest specimens in most populations are females.
M. Longevity. Unknown.
N. Feeding Behavior. The diet of western red-backed salamanders consists of small invertebrates including annelids, isopods, snails, spiders, mites, millipedes, centipedes, pseudoscorpions, and insects such as collembolans, dipterans, lepidopterans, and hymenopterans—including ants (Dumas, 1956; Nussbaum et al., 1983; Petranka, 1998).
O. Predators. Poorly documented but are known to (or probably) include common garter snakes (Thamnophis sirtalis; Norman, 1988b), shrew-moles (Neurotrichus gibbsi; Dumas, 1956), American dippers (Cinclus mexicanus; Dumas, 1956), and carabid beetles (Ovaska and Smith, 1988; Petranka, 1998).
P. Anti-Predator Mechanisms. Western red-backed salamanders rarely assume anti-predator postures when approached by carabid beetles in laboratory settings (Ovaska and Smith, 1988).
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. This is a widespread species that occurs in a variety of habitats. Rocky substrate is a key habitat need, but forest age is not. The species appears not to be declining at the present time.
1R. Bruce Bury
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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