Garden Slender Salamander
Harold C. Bryant
© Museum of Vertebrate Zoology, University of California, Berkeley (1 of 21)
Batrachoseps major Camp, 1915
Robert W. Hansen1
1. Historical versus Current Distribution. Garden slender salamanders (Batrachoseps major) are found in southern California from the southern foothills of the Santa Monica, San Gabriel, and San Bernardino mountains south along the Pacific Coast to the vicinity of El Rosario, Baja California (Wake and Jockusch, 2000). Populations extend eastward via San Gorgonio Pass to the margins of the Colorado Desert, occurring south of Cabazon (Wake and Jockusch, 2000), in Snow Creek Canyon (D.B.W., unpublished data), and within the city of Palm Springs (Cornett, 1981). They also are found on Santa Catalina, North, Middle, and South Coronados, and Todos Santos islands. Garden slender salamanders have been introduced at Hanford, Kings County, in the San Joaquin Valley of central California, 250 km north of their natural range (Jockusch, 1996). They occur from sea level to 1,500 m (Mt. Palomar, San Diego County), but most populations are found below 700 m elevation.
2. Historical versus Current Abundance. While formerly widespread and common in southern California, garden slender salamanders have been extirpated from much of their historical range due to habitat destruction (Cunningham, 1960; Wake, 1996). DeLisle et al. (1986) recorded garden slender salamanders from only two sites along the southern base of the Santa Monica Mountains (lowland areas that have experienced substantial habitat loss) but found black-bellied slender salamanders (B. nigriventris) at 31 localities from higher elevations, where native habitats have been less affected by development.
3. Life History Features.
A. Breeding. Reproduction is terrestrial.
i. Breeding migrations. Seasonal movements associated with reproductive activity have not been described. Although unrecorded, courtship probably occurs in the fall (November–December) after the start of the rainy season. Groups of 15–20 adults have been found under single cover objects in spring (B. Campbell, in Stebbins, 1951), but such aggregations are unlikely to be related to breeding activity.
ii. Breeding habitat. Unknown. Eggs are laid underground in burrows (Cunningham, 1960), but the location of spermatophore deposition and capture is unrecorded.
i. Egg deposition sites. Eggs are laid underground. At night in late January, hatchlings were observed in groups of 3–12 near burrows following heavy rains (Cunningham, 1960), suggesting that eggs had been deposited underground in burrows. Communal nesting (Jockusch and Mahoney, 1997) is suggested by the mass emergence of 158 hatchlings following heavy rains in late January; salamanders had emerged from a 4–5 mm crack between the wall of a house and a concrete landing (Grant, 1958).
ii. Clutch size. Davis (1952) discovered a clutch of 13 freshly laid eggs; by 18 January, five additional eggs were observed, though it is unknown whether these were deposited by the same female. Two adult females collected in mid December contained 15 and 20 fully developed ova (Stebbins, 1951).
C. Direct Development. In the northern part of the range (Los Angeles County), eggs are deposited in December–January (Stebbins, 1951; Davis, 1952), with hatchlings first appearing in late January. Hatchlings have been observed as late as mid April in northern San Diego County (Holland and Goodman, 1998).
D. Juvenile Habitat. Differences in habitat use between juveniles and adults have not been noted.
E. Adult Habitat. Prior to extensive modification of southern California native landscapes, garden slender salamanders occupied areas of coastal sage scrub, chaparral, and coast live oak woodlands, mostly in open areas with little relief (Camp, 1915; Stebbins, 1951, 1954a; Wake, 1996). Such areas experience a mild, dry summer–wet winter climate, often with coastal fog. In the San Gabriel Mountains, garden slender salamanders occur mostly in the foothills, but occasionally are found in oak woodland on alluvial fans (Schoenherr, 1976). In northern San Diego County, garden slender salamanders may be locally abundant in oak woodland and chaparral (Holland and Goodman, 1998). In present day southern California, garden slender salamanders frequently are associated with suburban landscapes that receive regular irrigation (Cunningham, 1960; Cornett, 1981). At their southern range limits at the edge of the Vizcaino Desert (26 km east of El Rosario, Baja California), garden slender salamanders have been found beneath decaying desert agave, at a site characterized by cardon cactus, boojum tree, and several species of Opuntia (Grismer, 1982).
On Santa Catalina Island, garden slender salamanders are found in coastal sage scrub (Schoenherr et al., 1999). On South Todos Santos Island off the Pacific Coast of northern Baja California, garden slender salamanders were found under rocks on a northeast-facing slope in early March (Zweifel, 1958).
The eastward extension of garden slender salamanders through San Gorgonio Pass to the margins of the Colorado Desert at Cabazon and Palm Springs suggests that they are tolerant of both heat and drought. However, these populations remain poorly studied. Although the Palm Springs region receives only 13.7 cm of annual precipitation, salamanders are now associated with residential and commercial landscapes that receive regular irrigation (Cornett, 1981); presumably these populations formerly experienced much shorter periods of surface activity corresponding to the brief rainy season. Some salamanders near Cabazon were found on the desert floor, although a few cottonwood trees grew nearby at a spring; during a cold rain in mid winter, one salamander was found under a dead stalk of a shrub on the open desert floor . The Cabazon site lies at the base of the San Jacinto Mountains in creosote bush desert (D.B.W., unpublished data).
The introduced San Joaquin Valley population is located in an area where summer daytime temperatures regularly exceed 37 ˚C and winter temperatures occasionally drop below freezing. Salamanders are confined to residential gardens with ornamental trees and shrubs that receive daily watering during the dry season (R.W.H., unpublished data).
Salamanders use gopher burrows, soil crevices, and earthworm tunnels for retreats (Lowe and Zweifel, 1951). One specimen was found 0.8 m below ground in a gopher burrow in early June (von Bloeker, 1942). During periods of surface activity, salamanders may be found under rocks, logs, boards, and other surface cover, as well as within moist leaf litter, mostly on coarse, well-drained substrates. Individuals occasionally are found climbing in low vegetation (Cunningham, 1960).
F. Home Range Size. Of 539 salamanders marked during a study in Santa Monica (Los Angeles County), 141 animals were recaptured at least five times; the maximum distance from point of last capture averaged 6.0 m (Cunningham, 1960). Juveniles tend to wander and have larger home ranges than adults.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Surface activity generally begins with the first significant rains of fall (October–November) and lasts into spring (April–May). However, in areas receiving coastal fog, activity may extend to June–July, and salamanders living in watered residential landscapes are active year-round (Cunningham, 1960). During a pitfall trapping survey on the western slope of Palomar Mountain (San Diego County), salamanders were captured from late December to late April and late December to late February over a 2-yr period (Powers and Banta, 1972).
Substrate temperatures for > 400 salamanders found under surface cover ranged from 4–21 ˚C, with most in the 9–11 ˚C range (Cunningham, 1960). Body temperatures averaged 12.9 ˚C for 53 salamanders (range 7.0–19.6 ˚C; Brattstrom, 1963; Feder et al., 1982). A cluster of six aestivating salamanders was unearthed 1 m below ground in moist soil (Cunningham, 1960). Four salamanders collected in mid February from the introduced San Joaquin Valley population had body temperatures of 12.0 ˚C (R.W.H., unpublished data).
I. Seasonal Migrations. Unknown.
J. Torpor (Hibernation). Body temperatures below 4.0 ˚C have not been recorded, and much of the range of garden slender salamanders rarely experiences nighttime temperatures below freezing.
K. Interspecific Associations/Exclusions. Garden slender salamanders are sympatric with black-bellied slender salamanders from southern Los Angeles County to the southern limits for black-bellied slender salamanders (B. nigriventris) in Orange and Riverside counties (Brame, 1970; Glaser, 1970; Wake, 1996). In areas where both species occur, there is a general pattern of ecological segregation, with garden slender salamanders occurring in open, grassy areas, mostly absent from slopes, while black-bellied slender salamanders are largely restricted to areas with tree cover (Campbell, 1931b; Lowe and Zweifel, 1951; Cunningham, 1960). However, at some sites with northern exposures, both species have been taken under the same cover (Campbell, 1931b).
Garden slender salamanders are sympatric with Monterey ensatinas (Ensatina eschscholtzii eschscholtzii) and arboreal salamanders (Aneides lugubris) at many localities, although the presence of garden slender salamanders in suburban gardens is unique among southern California salamanders.
L. Age/Size at Reproductive Maturity. Minimum adult size unknown. Age at sexual maturity has not been established, but Campbell (in Stebbins, 1951) found three size classes, which probably correspond to young of the year, 2 yr olds, and animals in their third year or older. The 2-yr group (46–60 mm TL) is clearly too small to be mature; thus, we suggest that likely minimum age for adults is 3 yr.
Geographic variation in adult size remains unstudied, although the largest animals have been recorded from the northern part of the range. Brame and Murray (1968) reported on a small series from Los Angeles County; nine adult females ranged in size from 50.1–67.5 mm SVL, and a single adult male measured 50.4 mm SVL. For another series, also from Los Angeles County, average size of nine adult males was 46.5 mm SVL (maximum 54.5 mm SVL), while average size of 13 adult females was 45.6 mm SVL (maximum 55.3 mm SVL). At the southern limits of the range (near El Rosario, Baja California), the largest individual in a series of 14 measured 45.2 mm SVL (Grismer, 1982). Stebbins (1985) reports a maximum size of 69 mm SVL, sex not indicated. Female-biased sexual size dimorphism is characteristic of most species of Batrachoseps for which data are available; it is unclear whether adult size differences exist in garden slender salamanders.
M. Longevity. Unknown.
N. Feeding Behavior. Prey reported for a Los Angeles County population studied by Cunningham (1960) included annelid worms, sow bugs, earwigs, and other insects.
O. Predators. Despite their broad distribution and local abundance in southern California, reports of natural predators of garden slender salamanders are rare. Ring-necked snakes (Diadophis punctatus) have been observed feeding on garden slender salamanders (Holland and Goodman, 1998; D. Holland, personal communication). Ervin et al. (2003) reported predation by a two-striped garter snake (Thamnophis hammondii). Feral pigs are reported to prey on the salamander species occurring on Santa Catalina Island, although specific reference to Batrachoseps is lacking (Schoenherr et al., 1999).
P. Anti-Predator Mechanisms. Individuals of garden slender salamanders may exhibit coiling, vigorous lateral thrashing, or immobility upon discovery or when handled (Cunningham, 1960; Schoenherr, 1976). Cunningham (1960) observed individual salamanders partly emerged from home burrows, with tail still anchored within the burrow; the salamanders would quickly retreat upon his approach. Garden slender salamanders consistently are the lightest-colored species of Batrachoseps, perhaps an example of crypsis, as Stebbins (1954a) noted their frequent association with light-colored substrates. Captive snakes (two-striped garter snakes [Thamnophis hammondii] and common kingsnakes [Lampropeltis getula]) died after consuming garden slender salamanders, presumably because of the effects of skin toxins (Cunningham, 1960). The discovery of two bodies and six tail tips of garden slender salamanders in the stomach of a two-striped garter snake clearly attests to the efficacy of tail autotomy as a defensive response in this species (Ervin et al., 2003).
Q. Diseases. Unknown.
R. Parasites. Unknown.
S. Comments. Although Wake and Jockusch (2000) provisionally included salamanders from the Sierra San Pedro Martir (Baja California) within B. major, work in progress suggests that this population warrants recognition as a distinct species (D.B.W. and colleagues, unpublished data) and thus we exclude it from this account. Following Wake and Jockusch (2000), we also exclude from B. major those populations occurring in coastal central California previously included within a large B. pacificus complex (Yanev, 1978, 1980; now consisting of four recently described species [Jockusch et al., 2001]), as well as populations on the northern Channel Islands, now accorded full species status as B. pacificus (Channel Islands slender salamanders).
Recent studies of allozymes and mitochondrial DNA sequences have led Wake and Jockusch (2000) to reduce B. aridus to subspecific status within B. major. The population of B. aridus analyzed for allozymes is no different from B. major than any of a number of other local populations. There are no fixed differences and no unique alleles. However, there is a unique haplotype for the mitochondrial gene cytochrome b, and it forms a sister group with a population from Todos Santos Island, off the coast of Baja California. These two populations are in turn sister to a group of populations assigned to B. major from San Diego County. We make no judgment about taxonomy, but choose to deal with 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.
MtDNA sequences confirm a Los Angeles County origin for the extralimital population of B. major now established in the southern San Joaquin Valley (Jockusch, 1996). Several large commercial nurseries in southern California supply plants to retail nurseries in central California; this seems a likely method for the transport of salamanders and eggs, or both.
4. Conservation. Much of the historical habitat of garden slender salamanders in southern California has been altered permanently by human development, thus fragmenting the range of this otherwise widespread species. Although portions of their range appear to be protected, examination of the relationships between genetically distinctive range segments of B. major and the long-term viability of native landscapes is needed.
Acknowledgments. We thank Dan Holland and Ted Papenfuss for sharing unpublished observations.
1 Robert W. Hansen
2 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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Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 23 Sep 2018.
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