A large, heavy, terrestrial salamander. Gilled adults are found in some populations. Transformed adults reach sizes of 17 - 30.5 cm total length and larval adults may reach 35 cm (Stebbins 1985; Petranka 1998). In transformed adults, the dorsal color is reddish brown overlain with copper-colored, coarse marbling. The marbling often extends to the chin, throat and undersides of the forelimbs (Nussbaum 1976). Young metamorphs have bright, golden marbling. Larvae are the stream type and have short, bushy gills and a low tail fin that extends forward to the hindlimb insertion. Larval coloration is light brown above with a white to yellowish venter. The tail lacks the conspicuous blotching seen in larval D. tenebrosus. A yellow stripe is usually present behind the eyes and the tips of the digits are black and cornified (Petranka 1998).
 
On the basis of genetic differentiation, D. tenebrosus was recently recognized as a species distinct from D. ensatus (Good 1989). The genus Dicamptodon was historically included as a subfamily (Dicamptodontinae) in the family Ambystomatidae, and was placed in a separate family, Dicamptodontidae, based on features of the spinal nerves (Edwards 1976).

See another account at californiaherps.com.

This species can be found in west-central California, USA (Good 1989). It also occurs from Sonoma and Napa Counties south to Santa Cruz County and to Monterey County (Petranka 1998). It is found from 0-900m asl.

The Pacific Giant Salamander is found along the West Coast of North America from northern California to southern British Columbia. Its range in British Columbia is only about 250 square kilometers, a meager 0.03% of the province. It is also only found in a limited area in California.

Biogeographic Regions: nearctic (Native )

endemic to a single state or province

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (5000-20,000 square km (about 2000-8000 square miles)) Range includes only west-central California (Good 1989); Sonoma and Napa counties south to to Santa Cruz County and disjunctly to Monterey County (Petranka 1998).

Restricted to Coast Ranges in California, from Sonoma and Napa counties south to Santa Cruz county with a geographic isolate in Monterey county (Stebbins 1985; Petranka 1998). Giant salamanders inhabit humid, forested areas, and are found in and around permanent and semi-permanent streams. Larvae are more abundant than adults and tend to occur in small to medium sized mountain streams. Adults are rare, but occasionally can be found under rocks and logs near, or under rocks in streams during the breeding season (Petranka 1998).

Like all salamanders, the Pacific Giant has an aquatic larval stage, and a terrestrial adult stage. The adult is stout-bodied with a long tail. It is very large, usually 30 centimeters or more in length. Its tail is about 40% of its total length, and is laterally compressed as an aid for swimming. The Giant Salamander has four toes on the front feet, and five toes on the hind feet. Pacific Giant Salamanders are often identified by their coloring. They have a distinct pattern of dark blotches on a light brown almost brassy-colored background. Color is known to vary widely within the range of this species.

Larvae of the Pacific Giant Salamander are streamlined and adapted for life in flowing water. They have small "fuzzy" gills behind their heads and a fin along the top and bottom of their tails.

Length: 30 cm

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

The Pacific Giant Salamander is found in a variety of aquatic habitats, including lakes, ponds, rivers, and streams. They prefer fast moving water to slow moving water. Cover is another vital characteristic of this Salamander's habitat. Cover is used for hiding, protection from the sun, and brooding eggs.

Aquatic Biomes: lakes and ponds; rivers and streams

Comments: Larvae usually inhabit clear, cold streams but are also found in mountain lakes and ponds. Adults are found in humid forests under rocks and logs, etc., near mountain streams or rocky shores of mountain lakes (Stebbins 1985). Eggs usually are laid in headwaters of mountain streams, in water-filled chambers under logs and rocks or in rock crevices.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Migrates between aquatic breeding and terrestrial nonbreeding habitats.

The adult and larval forms of the Pacific Giant Salamanders are predators. Adults feed on land snails and slugs; insects such as beetles, caddisfly larvae, moths and flies. They also eat small mammals such as shrews and white-footed mice; and other amphibians. Larvae feed on absolutely anything that comes near them. This includes insects, snakes, and small fish. In an experiment they were shown to grab anything attached to a hook, and refuse to let go of it, even when dragged from the water.

Comments: Larvae feed on a wide variety of aquatic invertebrates as well as some small vertebrates (e.g., fishes, tadpoles, other larval salamanders). Adults eat terrestrial invertebrates, also small snakes, shrews, mice, and salamanders, etc.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: Unknown

Comments: Information not available; very difficult to survey (D. Wake, pers. comm., 1997).

2500 - 10,000 individuals

Comments: Total adult population size in unknown but likely is at least several thousand. Locally abundant (J. Petranka, pers. comm., 1997). Terrestrial adults are far less abundant than the aquatic larvae (Petranka 1998). Specific information not available (D. Wake, pers. comm., 1997).

Usually reaches sexual maturity in both larval and terrestrial forms at sizes > 115 mm SVL (Nussbaum et al. 1983).

Average lifespan

Status: captivity: 16.9 years.

Maximum longevity: 16.9 years (captivity)

Mature adults migrate to suitable streams or springs for breeding. This is believed to occur from spring to autumn, but not much is really known. The female deposits from 85 to 200 eggs, singly or in clumps, in a hidden subterranean or underwater nest site. The female protects these eggs for up to seven months. She aggressively protects them from being cannibalized by males or eaten by other predators, and eats little or nothing herself. When the larvae finally hatch, they live in the nest for another two to four months. During this time they do not feed but get energy from their yolk. Because of this long gestation period, females are only able to reproduce once every two years. They also do not reach sexual maturity until they are five or six years old. These things combined with the small number of eggs laid give this animal a relatively slow reproductive rate.

Breeds both spring and fall. Lays clutch of 135-200 eggs in spring. Female guards eggs until hatching. Larvae metamorphose usually in 18-24 months, but sometimes paedomorphic (Nussbaum et al. 1983, Stebbins 1985).

The Pacific Giant Salamander is a rare species due to several factors, the most important of which are limited range, human activities, severe weather, and predation. The Pacific Giant Salamander is protected from killing or collecting under the Wildlife Act in British Columbia. It has been "red-listed" by British Columbia, meaning that it is being considered for "threatened" or "endangered" status.

IUCN Red List of Threatened Species: near threatened

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Small range in west-central California; trend and abundance are not well documented; greatest threats are habitat fragmentation and degradation due to land use changes, including urbanization, agriculture, and timbering; probably only moderately threatened due to presence in numerous protected areas.

Intrinsic Vulnerability: Moderately vulnerable

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Population

Population Trend

Global Short Term Trend: Unknown

Comments: No population information is available to determine trends (D. Wake, pers. comm., 1997).

Little is known about the biology of the terrestrial adult. Information on mating and courtship is not available. Nests of D. ensatus have been found below cover objects (rocks and longs) submerged in running water. Clutch size ranged from 70 - 100 eggs (Petranka 1998). Dicamptodon ensatus are probably similar to other species of Dicamptodon in many features. Larval diet has not been studied, but presumably includes aquatic invertebrates and some aquatic vertebrates, as seen in D. copei (Nussbaum et al. 1983). Juveniles and adults forage above ground on rainy nights and can sometimes be found on rural roads. Adult D. ensatus have been reported to eat smaller D. ensatus. Birds and shrews may also prey on D. ensatus, but they have to contend with a strong defensive bite (Petranka 1998). Dicamptodon ensatus are known to vocalize (Stebbins 1951). Larvae reach high densities are likely an important component of stream communities (Petranka 1998).

Major Threats

Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable

Comments: The greatest threats are stream siltation and urban development (Petranka 1998; D. Wake, pers. comm., 1997). Threatened by habitat fragmentation due to land use changes, including urbanization, agriculture, and timbering (Welsh, pers. comm., 1997). Although the range is small and close to urban areas, the species probably is only moderately threatened since it occurs on numerous protected areas (D. Wake, pers. comm., 1997).

In the related Pacific giant salamander (D. tenebrosus), larvae may be reduced in numbers where there has been clear-cut logging (Corn and Bury, 1989) 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 D. tenebrosus (Murphy and Hall, 1981).

This species has a small range and is threatened by logging and development. Stream siltation is a particular problem for the larvae (Petranka 1998).

Conservation Actions

Biological Research Needs: Determine life history and habitat requirements (Petranka, in press). Determine fragility and movement ecology.

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Occurs in numerous state and national parks. These areas are not free from disturbance, due to high recreational use (D. Wake, pers. comm., 1997).

The Pacific Giant Salamander is sold as a pet in the United States where it is more common then in British Columbia.

Comments: Good (1989) examined genetic relationships and concluded that the genus Dicamptodon comprises 4 species: D. ENSATUS (west-central California), D. ATERRIMUS (Rocky Mountains of Idaho and adjacent Montana; see also Daugherty et al. (1983), D. TENEBROSUS (southern British Columbia to northern California), and D. COPEI (Washington and northern Oregon). A previous study of morphological variation (Nussbaum 1976) concluded that Dicamptodon includes only 2 species, COPEI and ENSATUS (the latter including ATERRIMUS and TENEBROSUS). TENEBROSUS and ENSATUS hybridize in narrow zone in northern California, but there appears to be selection against hybrids, and introgression beyond the hybrid zone apparently is nonexistent (Good 1989).