Gabilan Mountains Slender Salamander
© 2019 Gary McDonald (1 of 13)
Batrachoseps gavilanensis Jockusch, Yanev and Wake, 2001
Robert W. Hansen1
1. Historical versus Current Distribution. Gabilan Mountains slender salamanders (Batrachoseps gavilanensis) were described in 2001 on the basis of differences in allozymes and in DNA haplotypes in the mitochondrial gene cytochrome b (Jockusch, 1996; Jockusch et al., 2001). Gabilan Mountains slender salamanders are broadly distributed and currently known from many locations in central coastal California (Jockusch et al., 2001). The northernmost known location is Rodeo Gulch, Santa Cruz County. From there, populations are found southward to the Pacific Coast, and along the coast to the eastern edge of the city of Monterey. They are found in Monterey on Jack's Peak, Monterey County. South of the Monterey Peninsula, populations do not occur along the coast, but instead extend southeast to the south-central portions of Monterey County.
The northern boundary of the range of Gabilan Mountains slender salamanders extends from Santa Cruz east along the base of the Santa Cruz Mountains. From there populations extend southeast into the Gabilan Range and other mountains in San Benito County, onto Mustang Ridge in extreme eastern Monterey County. Inland locations include Coalinga Mineral Springs, western Fresno County, and the Cholame region of southeastern Monterey and northeastern San Luis Obispo counties, extending into the northwestern tip of Kern County. Preserved specimens from the Temblor Range in Kern County are tentatively assigned to this species (Jockusch et al., 2001). The elevational range is from near sea level to about 880 m (headwaters of San Benito River at Fresno/Monterey county line). Differences between historical and current distributions are not apparent.
2. Historical versus Current Abundance. Aside from local extirpations associated with development and agriculture, populations appear stable.
3. Life History Features.
A. Breeding. Reproduction is terrestrial.
i. Breeding migrations. Unknown.
ii. Breeding habitat. Unknown.
i. Egg deposition sites. Oviposition sites are unknown. Egg attendance by females and communal nesting are unknown for this species.
ii. Clutch size. Unknown.
C. Direct Development. This species lays eggs that undergo direct development. Eggs have been laid in the laboratory but no field observations have been made as yet.
D. Juvenile Habitat. Differences between juvenile and adult habitat use are not apparent.
E. Adult Habitat. Gabilan Mountains slender salamanders are found in a variety of habitats from deeply shaded, moist redwood and mixed coniferous forests through oak woodland and chaparral to open grassland with widely scattered small oaks. The northwesternmost localities have cool, equable climates and rainfall that can exceed 100 cm annually; the southeasternmost localities are hot and dry during the summer, with annual rainfall < 20 cm. Indeed, populations occurring in the southern Diablo Range (e.g., Coalinga Mineral Springs, Fresno County) and the northern Temblor Range (e.g., Cottonwood Pass, Kern County) occur in climatically harsh settings rarely occupied by members of this genus; these populations appear to be widely scattered and localized and are restricted to relatively mesic north-facing slopes in otherwise arid oak woodlands or chaparral.
F. Home Range Size. Unknown.
G. Territories. Unknown.
Aestivation/Avoiding Dessication. Salamander activity closely tracks the rainy season
(largely December–April), especially in the warmer and drier southern and eastern
parts of the range. Northern and coastal populations may remain surface active
into the summer. Body temperatures (inferred from substrate temperatures) for a
small series of adult and juvenile Gabilan Mountains slender salamanders found on 24
March in Fresno County averaged 12.1 ˚C (range 11.5–12.5 ˚C; n = 16).
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. North of Monterey Bay, Gabilan Mountains slender salamanders are found in sympatry with California slender salamanders (B. attenuatus) along an ecotone between upland redwood forests and lowland oak habitats. One such area is Hecker Pass at the southern end of the Santa Cruz Mountains (near Santa Cruz-Santa Clara county line), where both species are locally sympatric. Along the southwestern edge of their range, on Mustang Ridge and Peachtree Valley, Monterey County, and Coalinga Mineral Springs, Fresno County, Gabilan Mountains slender salamanders and black-bellied slender salamanders (B. nigriventris) are found in microsympatry except on steep slopes with scattered foothill pine and juniper (Jockusch et al., 2001). On Jacks Peak, along Carmel Valley and near Arroyo Seco, Monterey County, sympatry is expected between Gabilan Mountains slender salamanders and Santa Lucia Mountains slender salamanders (B. luciae) but has not been confirmed. These two species have been taken within 200 m of each other in southwestern Monterey County.
Gabilan Mountains slender salamanders are ecological equivalents of B. attenuatus and B. nigriventris; all three species are relatively widely distributed and occur over a broad range of ecological settings. These species replace one another geographically, with only limited range overlap, suggesting that range expansion might be limited by competition.
L. Age/Size at Reproductive Maturity. This is a moderately small species of Batrachoseps, although individuals attain larger sizes than other central coastal species of the B. pacificus complex. Based upon measurements of a small series, males ranged from 39.4–46.7 mm SVL (mean 43.1 mm; n = 10), females from 38.8–50.6 mm SVL (mean 43.9 mm; n = 10) mm.
M. Longevity. Unknown.
N. Feeding Behavior. Gabilan Mountains slender salamanders, similar to other species of Batrachoseps, capture small insect prey using their projectile tongue.
O. Predators. Unknown, although snakes, birds, and small mammals are likely predators.
P. Anti-Predator Mechanisms. Coiling is a common defensive response in several species of Batrachoseps.
Q. Diseases. Unknown.
R. Parasites. Unknown.
S. Comments. Although only recently described, specimens now referred to this species have been in scientific collections for many years though assigned to other taxa (e.g., B. attenuatus [Hendrickson, 1954] and later, B. relictus [Brame and Murray, 1968] and B. pacificus [Yanev, 1980]). Yanev (1978, 1980), on the basis of allozymes, first identified the major lineages within the central coastal B. pacificus complex. Subsequently, these have been recognized as four distinct species (gavilanensis, incognitus, luciae, and minor [Jockusch et al., 2001]). Based on studies of mtDNA and allozymes, it seems likely that B. gavilanensis is the most basal member of the pacificus group (Jockusch and Wake, 2002). There is some evidence that B. gavilanensis and B. luciae might have been in genetic contact early in their history, although there is no indication of present gene exchange despite sharing a long border through Carmel Valley (Jockusch et al., 2001).
4. Conservation. Gabilan Mountains slender salamanders are moderately widespread throughout their range and appear to be common at a number of localities. Portions of their range occur on publicly owned lands or other large land holdings that are likely to remain relatively undisturbed for the foreseeable future. Aside from local extirpations associated with human development, there are no known critical conservation concerns. Surveys for this species might be complicated by the closely similar appearance of Batrachoseps attenuatus and B. nigriventris—species that have ranges that partly overlap that of B. gavilanensis and are extremely difficult to distinguish in the field.
1Robert W. Hansen
2David B. Wake
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 11 Aug 2020.
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