The following account is modified from Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo (©2005 by the Regents of the University of California), used with permission of University of California Press. The book is available from UC Press.

Batrachoseps aridus Brame, 1970
Desert Slender Salamander

Robert W. Hansen¹
David B. Wake²

1. Historical versus Current Distribution. Desert slender salamanders (Batrachoseps aridus) were discovered in 1969 from Hidden Palm Canyon (760 m elevation), a tributary of Deep Canyon on the eastern flank of the Santa Rosa Mountains, Riverside County, California (Brame, 1970). This remained the only known population until the discovery of salamanders along Guadalupe Creek (945–1,097 m elevation), about 4.5 air miles from the type locality (Giuliani, 1981; Wake and Jockusch, 2000). These two sites constitute the only known localities for the species (Wake, 1996). Available habitat for Hidden Palm Canyon (about 0.2 ha; Bleich, 1978) and Guadalupe Canyon (about 0.6 ha; Duncan and Esque, 1986) combines for one of the most restricted distributions of any North American salamander.

Portions of the Hidden Palm Canyon habitat were destroyed by a severe storm in 1976. Damage included loss of limestone sheeting and underlying soil on the canyon wall, as well as scouring of the canyon bottom to a depth of about 2 m (Bleich, 1978). Other parts of the canyon retain viable habitat (K. Nicol, personal communication).

2. Historical versus Current Abundance. Brame (1970) and subsequent workers found desert slender salamanders to be extremely localized but common within Hidden Palm Canyon. For example, during single visits Brame and colleagues found 8 specimens in February 1970, 11 specimens in March 1970, 10 specimens in July 1970, 39 specimens in March 1971, and 25 specimens in March 1972 (Brame, 1970; Brame et al., 1973). Bleich (1978) found as many as 21 salamanders in one night in the 1977–'78 field season. Giuliani (1981) observed 16 individuals in one night in January 1981, although most of these were juveniles. More recent searches (since 1995) confirm the presence of salamanders in Hidden Palm Canyon, although estimates of abundance are lacking (Brame and Hansen, 1994; K. Nicol, personal communication). Comparing the field results of Brame and colleagues (who relied on movement of surface cover to locate specimens) with more recent searches is difficult owing to the passive search techniques employed by later workers to minimize disturbance of the fragile habitat.

Within Guadalupe Canyon, salamanders have been found at discrete sites over approximately 1.6 linear km (1 mi) of riparian canyon-bottom habitat. However, numbers of salamanders at a given locality are much lower than in Hidden Palm Canyon. Duncan and Esque (1986), for example, never found > 4 salamanders at any one locality/visit.

3. Life History Features.

A. Breeding. Reproduction is terrestrial.

i. Breeding migrations. Unknown. We expect that breeding movements are similar to garden slender salamanders (Batrachoseps major), their close phylogenetic relatives.

ii. Breeding habitat. Unknown.

B. Eggs.

i. Egg deposition sites. Oviposition sites are unknown. Presumably, desert slender salamander females deposit egg clutches deep within limestone crevices (Hidden Palm Canyon) where moisture may be present year-round. Egg attendance by females and communal nesting are unknown for this species.

ii. Clutch size. Unknown.

C. Direct Development. Although unreported, we presume that desert slender salamanders undergo direct development, as is the case with other species of bolitoglossine plethodontids. Dates of hatching are unknown.

D. Juvenile Habitat. It is unknown how this may differ from adult habitats.

E. Adult Habitat. Desert slender salamanders exist in seep formations and other localized moist areas within steep-sided, protected canyons on the eastern (desert-facing) slope of the Santa Rosa Mountains. Salamander sites are beyond the reach of direct sunlight year-round. Mesic-associated vegetation at the Hidden Palm Canyon site includes sugar bush, willow, Washington palms, creosote, mesquite, and various grasses and mosses. Bordering slopes display typical desert plant species (e.g., cholla, agave, barrel cactus, prickly pear cactus, creosote, juniper, and mesquite). Within Guadalupe Canyon, the following plants are characteristic of salamander sites: maidenhair fern, Fremont cottonwood, willows, waterweed, deer grass, California fuschia, wild grape, sugar bush, and scrub oaks. Now considered extinct.

Although individual desert slender salamanders have been found beneath rocks resting on damp substrates, perhaps the most important element of the Hidden Palm Canyon habitat is the numerous crevices and fissures present in the limestone rock formations (U.S.F.W.S., 1982). These permit moisture to move through crevices and provide critical refugia for salamanders. This may be critical in sustaining the population following stochastic events, such as severe storms, that result in significant modification to surface habitat.

During the active season, desert slender salamanders move at night from locations deep in the recesses of crevices to the crevice openings to capture food. Thus, diurnal searches for this species that rely on examination of surface cover may seriously underestimate the number of individual salamanders present. Nighttime searches using a flashlight to examine moist crevices, together with use of artificial cover objects (plastic garbage bags), are more effective and minimize potential impact to the habitat (Duncan and Esque, 1986; Palazzo, 1994; Duncan, 1998).

F. Home Range Size. Unknown.

G. Territories. Unknown.

H. Aestivation/Avoiding Dessication. Salamanders have been observed surface active or under cover mostly during the winter, although Brame (1970) found animals in July under porous limestone, suggesting that activity continues into the summer at Hidden Palm Canyon. Conditions were too dry in Guadalupe Canyon in July for surface activity (Duncan, 1998).

I. Seasonal Migrations. Unknown.

J. Torpor (Hibernation). Unknown. Potentially, low winter temperatures (≤ 5 ˚C) would preclude activity, but this remains unstudied.

K. Interspecific Associations/Exclusions. Unknown. This is the only salamander species within the range.

L. Age/Size at Reproductive Maturity. Unknown. Based upon measurements of a small series and comparisons with other species of Batrachoseps, we estimate that sexual maturity is attained at 31 mm SVL in males and at a slightly larger size in females. The largest individuals are females (maximum SVL 48.4 mm).

M. Longevity. Unknown.

N. Feeding Behavior. Bleich (1978) observed feeding at night on two occasions, with salamanders capturing small insect prey using their projectile tongue.

O. Predators. Bleich (1978) speculated that western skinks (Eumeces skiltonianus) and ring-necked snakes (Diadophis punctatus) were potential predators, although the latter species is unrecorded from desert slender salamander sites.

P. Anti-Predator Mechanisms. Brame et al. (1973) reported that when uncovered in the field, about 75% of desert slender salamanders would coil their body while elevating their tail. Although coiling is a common defensive response in several species of Batrachoseps, the combination of body coiling and tail elevation is apparently unique to desert slender salamanders. Most of the specimens encountered by Bleich (1978) coiled tightly with the tail in a horizontal position or slightly elevated; the head was either on top of the body coil or hidden beneath.

Q. Diseases. Unknown.

R. Parasites. Unknown.

S. Comments. The taxonomic status of desert slender salamanders has been called into question by recently published analyses of allozymes and mtDNA (cytochrome b) sequences (Wake and Jockusch, 2000). With respect to allozymes, desert slender salamanders are no different than a local population of garden slender salamanders and are deeply nested within that taxon. Thus, continued recognition of desert slender salamanders (B. aridus) would render garden slender salamanders (B. major) paraphyletic. With respect to mtDNA sequences, desert slender salamanders have a unique haplotype (shared by the two populations) that is most similar to those found in a population of undetermined status (but which appears to be identical to B. major from the mainland) from Isla Todos Santos off the northwestern coast of Baja California. In turn, all of these haplotypes cluster with a phylogeographic segment of B. major from San Diego County. Wake and Jockusch (2000) recommend that B. aridus be treated as a subspecies of B. major because they differ from that taxon in morphology and possibly in ecology. We make no judgment about taxonomy, but choose to handle B. aridus as a separate entity for this work because of its status as a Federally protected Endangered species, which would not change regardless of its formal taxonomy.

4. Conservation. Desert slender salamanders are listed as Endangered at both state and federal levels. All parts of their known range occur on public lands adminstered by the U.S. Bureau of Land Management or the California Department of Fish and Game. The Hidden Palms Ecological Reserve, harboring the largest population, is closed to public access.

Acknowledgments. Todd Esque (U.S. Geological Survey), Derham Giuliani, and Kim Nicol (California Department of Fish and Game) provided unpublished reports or other information derived from their fieldwork with Batrachoseps in the Santa Rosa Mountains. Gavin Wright and Larry Foreman (Bureau of Land Management) also provided copies of reports from BLM files.

¹ Robert W. Hansen
16333 Deer Path Lane
Clovis, California 93611-9735
rwh13@csufresno.edu

² David B. Wake
Museum of Vertebrate Zoology
3101 Valley Life Sciences Building #3160
University of California
Berkeley, California 94720-3160
wakelab@uclink4.berkeley.edu

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 27 Dec 2024.

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