San Gabriel Mountains Slender Salamander
© 2011 Chris Brown, USGS (1 of 11)
Batrachoseps gabrieli Wake, 1996
Robert W. Hansen1
1. Historical versus Current Distribution. San Gabriel Mountains slender salamanders (Batrachoseps gabrieli) recently have been described (Wake, 1966) and are known from 13 discrete localities along the southern flanks of the San Gabriel and San Bernardino mountains of southern California (Wake, 1996; Goodman et al., 1998; R.H.G., unpublished data). Their distribution is discontinuous, from San Gabriel Canyon in the San Gabriel Mountains, Los Angeles County, east to Waterman Canyon in the San Bernardino Mountains, San Bernardino County (Stewart et al., in press). Elevation ranges from near 850–2,380 m. All sites occur on public lands administered by Angeles and San Bernardino National Forests.
2. Historical versus Current Abundance. San Gabriel Mountains slender salamanders are difficult to find at most sites. The number of animals found/visit has ranged from 0–31, but a more typical yield is 1–4 specimens. The difficulty of discovering animals under surface cover may be attributable to their occurrence in often-extensive talus, where salamanders may be present well below the top layer of rocks and thus are not readily observed.
3. Life History Features.
A. Breeding. Reproduction is terrestrial.
i. Breeding migrations. Unknown.
ii. Breeding habitat. Courtship and oviposition may occur following the first heavy rains in the fall.
i. Egg deposition sites. Nest sites have not been located. Considering the close association of San Gabriel Mountains slender salamanders with talus, it seems likely that eggs are deposited deep in talus piles.
ii. Clutch size. Unknown.
C. Direct Development. Egg laying and hatching have not been observed. San Gabriel Mountains slender salamanders occur at mid to high elevations with surface activity restricted to southern California’s winter precipitation season from November–April (Wake, 1996; Stewart et al., in press). A single hatchling-sized salamander was discovered on 15 April in the South Fork Lytle Canyon (San Gabriel Mountains).
D. Juvenile Habitat. Differences between juvenile and adult habitat use have not been observed, although we have found subadults more often under branches and other small cover.
E. Adult Habitat. San Gabriel Mountains slender salamanders are southern California talus specialists. However, there are considerable differences in local habitats owing to variation in elevation, vegetation, and exposure. Most salamanders have been discovered in and around stable talus accumulations of various sizes, under rotting logs, bark, downed branches, fern fronds, and rocks (Wake, 1996; Goodman et al., 1998; Stephenson and Calcarone, 1999; Stewart et al., in press). The type locality (1,550 m, 1 km ESE of Crystal Lake, along Soldier Creek, San Gabriel Mountains) consists of a steep northwest-facing talus slope within mixed conifer forest (various species of pines, white fir, big-cone spruce, incense cedar, canyon live oak; Wake, 1996). Other populations occur at lower, drier, more exposed sites within chaparral communities. At Alpine Canyon (1,150 m, San Gabriel Mountains), San Gabriel Mountains slender salamanders are associated with isolated stands of big cone spruce in talus bordered by chaparral vegetation on a southwestern exposure.
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Surface activity is limited to the rainy season during the winter and early spring (November–April). A large majority of specimens have been found following significant rain/snow events. Animals have been observed and collected while snow was present on the ground (Wake, 1996; R.H.G., unpublished data). As the talus habitat dries, there is a sharp decline in surface activity and salamanders become increasingly difficult to find. A substrate temperature of 4.2 ˚C was recorded for three salamanders found beneath a rock in late March (Wake, 1996) and is probably close to the low temperature threshold for surface presence.
I. Seasonal Migrations. Unknown.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. San Gabriel Mountains slender salamanders occur in sympatry with black-bellied slender salamanders (Batrachoseps nigriventris) at some sites in the San Gabriel Mountains (Wake, 1996; R.H.G., unpublished data). Within the San Gabriel Canyon area, black-bellied slender salamanders are common in oak woodlands and in riparian settings (with alders and sycamores). They have not been found in the forested areas east of San Gabriel Canyon, where San Gabriel Mountains slender salamanders occur.
Garden slender salamanders (B. major) occur within 5.5 km of the nearest population of San Gabriel Mountains slender salamanders in San Gabriel Canyon, but occupy distinctly different habitats at generally lower elevations in this region.
L. Age/Size at Reproductive Maturity. Adult males are 39.8–46.3 mm SVL (mean = 42.4 mm); females are 41.0–50.0 mm (mean = 46.1 mm; Wake, 1996).
M. Longevity. Unknown.
N. Feeding Behavior. Small invertebrates captured with a projectile tongue. Field observations of San Gabriel Mountains slender salamanders scat indicate at least some consumption of ants (Crematogaster sp.; R.H.G., unpublished data).
O. Predators. Unknown.
P. Anti-Predator Mechanisms. Various reactions to discovery include coiling (Wake, 1996), immobility, or slowly crawling away; less often, salamanders have escaped by moving into deeper talus layers (R.H.G., unpublished data).
Q. Diseases. Unknown.
R. Parasites. Unknown.
S. Comments. Following the description of San Gabriel Mountains slender salamanders in 1996, careful searching in rockslide habitats has revealed additional populations. Although we provisionally include them in B. gabrieli, some of these recently discovered populations appear to have diverged genetically following long periods of isolation and may warrant recognition as a distinct species (D.B.W. and colleagues, unpublished data).
4. Conservation. The ecology of San Gabriel Mountains slender salamanders remains poorly known. All but two of the localities are represented by fewer than five specimens. Further searches of rockslide and talus habitats in the San Gabriel, San Bernardino, and San Jacinto mountains are needed. San Gabriel Mountains slender salamanders are a U.S. Forest Service Sensitive Species.
1 Robert W. Hansen
2 Robert H. Goodman Jr.
3 David B. Wake
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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