Dicamptodon ensatus Eschscholtz, 1833
California Giant Salamander
R. Bruce Bury1
1. Historical versus Current Distribution. California giant salamanders (Dicamptodon ensatus) are the southernmost taxa of four species in the genus (Good, 1989). They occur in the Pacific Coastal region around San Francisco Bay north to Mendocino, Sonoma, and Napa counties, and south to Santa Cruz County. A disjunct population exists farther to the south in Monterey County (Anderson, 1969; Nussbaum, 1976). There is little evidence to suggest the current distribution differs from the historical distribution, but populations have undoubtedly been lost with the intense urbanization and habitat alteration characteristic of many parts of their range.
2. Historical versus Current Abundance. Unknown, although it is likely that abundance is reduced in populations experiencing habitat modifications. In related Pacific giant salamanders (D. tenebrosus), larvae may be reduced in numbers where there has been clear-cut logging (Corn and Bury, 1989a) or siltation from roads (Welsh and Ollivier, 1998). However, opening of forest canopies over streams may lead temporarily to higher primary productivity that in turn increases the body sizes of larval Pacific giant salamanders (Murphy and Hall, 1981).
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. Unknown.
ii. Breeding habitat. During the breeding season, adults are found under stones in streams, but information on courtship behavior is not available.
i. Egg deposition sites. Subterranean habitats in running water (Henry and Twitty, 1940; Dethlefsen, 1948). On 17 June 1937, one nest of about 70 eggs was found attached to a submerged timber in a stream in the Santa Cruz Mountains, San Mateo County, California (Henry and Twitty, 1940); some eggs may have been lost in removing the timber from the stream bed. Dethlefsen (1948) reported on about 100 eggs and dismembered parts of two adult Dicamptodon that were ejected from a pipe drilled 6.1 m (20 ft) into a hillside spring in Santa Cruz County, California. Another live adult (243 mm TL) was in the pool outlet about 1 hr later. Three weeks later, another five adults were located under the same drilling station. No eggs appeared, but upon dissection, about 80 eggs were found in one female. All adults were weakly pigmented, suggesting they were underground for some time. Eggs are about 5.5 mm in diameter and attached singly to substrata such as rocks and logs by pedicels about 6 mm long.
ii. Clutch size. From 70 (Henry and Twitty, 1940) to about 100 eggs (Dethlefsen, 1948). Incubation time was suggested as extremely long at almost 5 mo (Henry and Twitty, 1940), but this was in the laboratory.
i. Length of larval stage. Perhaps 18 mo (Kessel and Kessel, 1943a,b, 1944; see also Petranka, 1998). Larvae are mountain brook type with a reduced tail fin and no balancers.
ii. Larval requirements.
a. Food. No data exist for food of California giant salamanders. Diet is most likely similar to related Pacific giant salamanders that feed on aquatic invertebrates, with a shift towards larger prey items with growth (Johnson and Schreck, 1969; Parker, 1994).
b. Cover. Younger larvae are found in slowly moving water near the shoreline, while older larvae tend to be found in the main stream channel (Kessel and Kessel, 1943a,b, 1944). Larvae often hide under gravel and cobble or other objects in streams.
iii. Larval polymorphisms. Unknown.
iv. Features of metamorphosis. Larvae metamorphose at about 130–140 mm TL in their second year of life (Kessel and Kessel (1943a,b).
v. Post-metamorphic migrations. Undocumented.
vi. Neoteny. Neotenic animals are present in many populations (De Marco, 1952; Nussbaum, 1976).
D. Juvenile Habitat. Probably similar to adult habitat.
E. Adult Habitat. California giant salamanders are associated with permanent and semipermanent streams. Adults occasionally are found under cover objects, such as rocks and logs, or under stones in streams during the breeding season (see Petranka, 1998).
F. Home Range Size. Unknown.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Aestivation is unlikely; animals likely avoid dessicating condition by seeking shelter under cover objects.
I. Seasonal Migrations. Adults return to streams with the advent of fall rains (Kessel and Kessel, 1943a). In related Pacific giant salamanders, newly metamorphosed juveniles (Nussbaum et al., 1983) and sometimes neotenic adults (Welsh, 1986) move away from streams in rainy periods.
J. Torpor (Hibernation). Unknown, but unlikely.
K. Interspecific Associations/Exclusions. There is a hybrid zone between D. ensatus and D. tenebrosus about 10 km north of Gualala, Mendocino County, California (Good, 1989).
L. Age/Size at Reproductive Maturity. Adults measure 170–305 mm TL (Nussbaum, 1976; see also Petranka, 1998).
M. Longevity. Unknown.
N. Feeding Behavior. Includes a range of invertebrate prey and small vertebrate prey (Bury, 1972), including conspecifics (Anderson, 1960).
O. Predators. Likely include large birds, small mammals, and other vertebrates, including garter snakes (Thamnophis couchii; Lind and Welsh, 1990).
P. Anti-Predator Mechanisms. Antipredator posturing has not been documented in California giant salamanders, but Pacific giant salamanders have an arched posture and will release toxins when disturbed (Nussbaum et al., 1983). Unlike most salamanders, California giant salamanders can emit a vocalization that resembles a bark (Stebbins, 1951).
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. The current distribution of California giant salamanders likely does not differ from the historical distribution, but populations have undoubtedly been lost due to the intense habitat alterations characteristic of many parts of their range. According to Petranka (1998), because California giant salamanders have a small range that exists within an area of intense human activity, they are at threat from siltation of their stream habitats and urbanization.
1R. Bruce Bury
USGS Forest and Rangeland Ecosystem Science Center
3200 Southwest Jefferson Way
Corvallis, Oregon 97331
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 14 Nov 2018.
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