Black-bellied Slender Salamander, Blackbelly Slender Salamander
© 2006 William Flaxington (1 of 34)
Batrachoseps nigriventris Cope, 1869
Robert W. Hansen1
1. Historical versus Current Distribution. Black-bellied slender salamanders (Batrachoseps nigriventris) are found in the coastal mountains and valleys west of the Central Valley of California, from extreme southern Monterey County and western and southern Fresno County to the Santa Monica and San Gabriel mountains of Los Angeles County. They also are found in the Tehachapi Mountains at the southern and eastern margins of the Central Valley. They also occur in isolated upland areas in southern Los Angeles County and in Orange and extreme southwest Riverside counties. Black-bellied slender salamanders are widely distributed on Santa Cruz Island. They occur from near sea level to about 2,260 m on Mt. Pinos (Wake and Jockusch, 2000). Recent range modifications are not evident, except for areas of obvious habitat modification in many parts of their historical range in southern California.
2. Historical versus Current Abundance. Black-bellied slender salamanders may be locally abundant at some times, but difficult to find at others. Long-term trends are not apparent.
3. Life History Features.
A. Breeding. Reproduction is terrestrial.
i. Breeding migrations. We have discovered seasonal aggregations of 12–20 black-bellied slender salamander adults (sex not determined) on Mt. Pinos, suggesting that adult females move to communal nesting sites. Adults have been observed moving across wet roads at night on Mt. Pinos (G. Keasler, personal communication).
ii. Breeding habitat. Unknown.
i. Egg deposition sites. Nest sites have not been located. However, our observations of adult aggregations under and within downed logs in seepages on Mt. Pinos (2,260 m elevation) are strikingly similar to the descriptions of egg-laying sites reported for their sister species, gregarious slender salamanders (B. gregarius [Jockusch and Mahoney, 1997]; reported as B. nigriventris).
ii. Clutch size. Unknown.
C. Direct Development. Timing of egg laying and hatching are poorly known. Black-bellied slender salamanders occur over a broad elevational range in diverse habitats—from lowlands that experience a mild, coastal climate to interior mountains that receive substantial winter snowfall, and it seems likely that periods of egg laying will vary accordingly. In southern California lowlands and foothills, eggs probably are laid in winter and hatch in winter and early spring. Adult aggregations have been found in July to early August at high elevations on Mt. Pinos, but eggs were not observed at this time.
D. Juvenile Habitat. Differences in habitat use between juveniles and adults have not been noted.
E. Adult Habitat. Black-bellied slender salamanders occupy a wide range of habitats, from semi-arid blue oak savannas at the northern limits of the range to moist, oak-filled canyons and pine-fir forest at higher elevations. Habitat extremes are illustrated in northern populations; near Comanche Point on the northern slopes of the Tehachapi Mountains, salamanders occur on semi-arid, grassy slopes, with only an occasional blue oak mixed with scattered granite outcrops; at Mt. Pinos (2,260 m elevation), salamanders are locally abundant in Jeffrey pine-white fir forests, especially in association with small streams and seepages. Elsewhere in the Tehachapi Mountains, the species is relatively common in canyons with extensive growths of canyon live and black oaks (Block and Morrison, 1998; R.W.H., unpublished data).
In southern California, south of the Tehachapi Mountains, black-bellied slender salamanders mostly are found in foothills and mountain canyons, usually within coast live oak woodlands and/or chaparral (Lowe and Zweifel, 1951; Cunningham, 1960; Schoenherr, 1976). These salamanders have been found on rocky, north-facing slopes covered with coastal sage scrub vegetation and some California buckeye at the ocean in southern Orange County.
Black-bellied slender salamanders are widely distributed on Santa Cruz Island, where they occur under rocks and scattered debris (e.g., old fence posts) in open grassland; under rocks, fallen branches and in leaf litter in oak woodland; in and under rotting branches and logs as well as under rocks; and in surface litter in pine forests, as well as under superficial surface cover in chaparral.
F. Home Range Size. Salamanders of the genus Batrachoseps generally are assumed to be sedentary (Hendrickson, 1954; Cunningham, 1960). The geographically restricted patterns of mtDNA haplotype distributions indicate that female movements are limited (Jockusch, 1996). Thus, although there may be some short-range surface movements associated with breeding and egg deposition (e.g., Jockusch and Mahoney, 1997), individual salamanders likely have small home ranges.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Salamander activity closely tracks the rainy season and is strongly influenced by local conditions. For example, in the open oak woodlands on the northern flanks of the Tehachapi Mountains, the soil dries rapidly following spring rains and it is likely that surface activity declines abruptly after March. However, in adjacent canyons with extensive oak forests and north-facing slopes, seasonal activity may extend to late April to early May. On Mt. Pinos, salamanders have been found throughout the summer in association with perennially moist microhabitats. In the San Gabriel Mountains, we have found black-bellied slender salamanders mostly during the winter, with surface activity usually associated with recent rainfall. In the Santa Monica Mountains, surface activity occurs mainly from January–April (De Lisle et al., 1986). Near the Pacific Ocean at the base of the Santa Ynez Mountains, marine air flows may extend surface activity to late May. Earthworm burrows and soil crevices are utilized as retreats when surface conditions deteriorate (Lowe and Zweifel, 1951). Body temperatures of salamanders found under surface cover averaged 9.8 ˚C (range = 6.0–14.0 ˚C, n = 40, mostly from Tehachapi Mountains populations; R.W.H., unpublished data) and 8.8 ˚C (range = 6.8–9.5 ˚C, n = 26, locality not stated; Feder et al., 1982). Stebbins (1951) reported finding 14 adults in early December in the Santa Monica Mountains and recorded body temperatures of 10.2–10.5 ˚C.
I. Seasonal Migrations. Unknown.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. Sympatric with garden slender salamanders (B. major) from southern Los Angeles County to the southern limits for black-bellied slender salamanders in Orange County (Brame, 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, both species have been taken under the same cover. Black-bellied slender salamanders and garden slender salamanders have been collected within a few meters of each other in southeastern Riverside County.
Black-bellied slender salamanders coexist broadly with Channel Islands slender salamanders (B. pacificus) on Santa Cruz Island, where both species tend to occupy similar habitats (Schoenherr et al., 1999), and they frequently are found in microsympatry.
Along the central California coast and interior uplands west of the Central Valley, in southern Monterey and northern San Luis Obispo counties, some overlap occurs with three recently described species that formerly were included in B. pacificus (B. gavilanensis, B. incognitus, and B. minor; Jockusch, 1996; Yanev, 1978, 1980; Jockusch et al., 2001).
Black-bellied slender salamanders are sympatric with Tehachapi slender salamanders (B. stebbinsi) in the Pastoria and Tejon Creek drainages of the Tehachapi Mountains, as well as at Fort Tejon (Jockusch, 1996; R.W.H., unpublished data). Although both species have been found under the same cover, Tehachapi slender salamanders are restricted to moist, north-facing slopes, where they favor areas of talus or downed logs; black-bellied slender salamanders exhibit a broader ecological distribution in these areas and are mostly absent from steep slopes (R.W.H., unpublished data). The northernmost Tehachapi Mountains population of black-bellied slender salamanders lies about 37 km south of the nearest locality, near the Kern River, of its close relative, gregarious slender salamanders; it seems likely that populations belonging to one or both species will be found in the intervening foothills.
Black-bellied slender salamanders are sympatric with talus-dwelling San Gabriel Mountain slender salamanders (B. gabrieli) at a few sites in the San Gabriel Mountains at elevations of 1,158–1,200 m, and the two species have been taken under the same cover (Wake, 1996).
Black-bellied slender salamanders are broadly sympatric with yellow-blotched ensatinas (Ensatina eschscholtzii croceater) in the Tehachapi Mountains and Mt. Pinos regions, and with Monterey ensatinas (E. e. eschscholtzii), arboreal salamanders (Aneides lugubris), and California newts (Taricha torosa) at many sites in coastal and southern California.
L. Age/Size at Reproductive Maturity. Stebbins (1985) lists adult size as 31–47 mm SVL, but this information should be regarded as preliminary, considering that black-bellied slender salamanders then included populations that are now referable to B. gregarius. In a small series of adult males from San Luis Obispo County, the average was 38.0 mm SVL (range 35.3–42.0 mm, n = 7; reported as B. attenuatus; Brame and Murray, 1968). A female from Big Oak Flat, Los Angeles County, measured 49.1 mm SVL.
M. Longevity. Unknown.
N. Feeding Behavior. Has not been described, although all Batrachoseps species observed thus far use a projectile tongue to capture small invertebrates.
O. Predators. Predation in the wild is undocumented, although captive ring-necked snakes (Diadophis punctatus) and nightsnakes (Hypsiglena torquata) have consumed black-bellied slender salamanders (R.W.H., unpublished data).
P. Anti-Predator Mechanisms. Individuals of black-bellied slender salamanders exhibit coiling, rapid crawling, and immobility upon discovery (Stebbins, 1951; Schoenherr, 1976; R.W.H., unpublished data), and tail autotomy may occur when the tail is grabbed or pinched.
Q. Diseases. Unknown.
R. Parasites. A single species of helminth, Batracholandros salamandrae, is recorded from black-bellied slender salamanders (Goldberg et al., 1998c).
S. Comments. Jockusch et al. (1998) recently demonstrated that black-bellied slender salamanders (as defined by Yanev, 1978, 1980) comprised, at minimum, two species: B. gregarius of the Sierra Nevada and B. nigriventris of the central coast and Tehachapi Mountains into southern California. However, based on studies of allozymes and mtDNA sequences, even this restricted B. nigriventris appears to consist of three distinctive lineages: a northern form including the Tehachapi Mountains and central coast north to Monterey County, an island form from Santa Cruz Island, and a southern form occurring from Ventura and Los Angeles counties to the southern and eastern margins of the species range (Wake and Jockusch, 2000). The southern form shows extensive phylogeographic structure.
4. Conservation. Black-bellied slender salamanders have a relatively wide distribution (Wake and Jockusch, 2000). Recent range changes are not evident, except for areas of obvious habitat modification in many parts of their historical range in southern California. Long-term trends in abundance are not apparent.
Acknowledgments. Stephen Goldberg provided information concerning parasites.
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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