Description
This salamander is the largest terrestrial salamander in the Pacific Northwest of North America and one of the largest terrestrial salamanders in the world (Petranka 1998). Body stout and powerful. Smooth skin. Dorsal ground color is dark brown or gray to black with well defined irregular marbling of purple to reddish brown. Degree of marbling varies among individuals and among populations. Underside is usually light colored: light brown to off-white. The posterior half of the tail is laterally compressed, and the head is depressed in front of the eyes.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Canada, United States

U.S. state distribution from AmphibiaWeb's database: California, Oregon, Washington

Canadian province distribution from AmphibiaWeb's database: British Columbia

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (58 records).

Near sea level to ca. 7000 ft. (2160 m). From extreme SW British Columbia to northern Sonoma County in California (Good 1989).

Adults inhabit damp, dense forests (especially Coastal Redwood and Douglas Fir), usually in the vicinity of streams or seepages. Found under logs, rocks, bark, or other objects or sometimes crawling in the open. Occasionally climbs and has been recorded to a height of 8 ft. (Stebbins 1951). Larvae are found in small to medium sized creeks and streams in habitat similar to that in which adults are found.

Life History, Abundance, Activity, and Special Behaviors
Adults are remarkable for salamanders in their voracious feeding habits. Small rodents such as shrews and mice are regular prey, as are other amphibians, insects, snails, and slugs (Leonard et al. 1993; Petranka 1998). Diller (1907) observed an eight inch Dicamptodon with a two foot garter snake in its jaws, held by its head and neck. Some supposed that the salamander was defending itself rather than feeding on the snake, as garter snakes are common predators of Dicamptodon (see references in Petranka 1998). However, a series of photos and field notes from the MVZ Archive provide evidence of predation of snakes by large larva of this salamander (Childers et al 2020). Both predator (salamander larva) and prey (garter snake) are specimens in the museum collection as proof of the predation event.

Adults are very good diggers and likely burrow at the base of a spring upon arrival of the autumn rains. Indeed, adults have been found under ground at a depth of 20 ft. (Dethlefson 1948).

Nests of 83 and 146 eggs, attended by females, have been found in rocky areas nears streams and seeps. One nest was under rocks 3 feet from the surface. Egg deposition is in the spring (early May) and hatching may occur up to 9 months later (Nussbaum 1969).

Adults are very powerful and can inflict a painful bite when handled. They are also known to emit an audible growl or bark when threatened (Stebbins 1951 1985). Adults are relatively rare and are a good find even in prime habitat, especially considering the abundance of the larvae in streams of the Pacific Northwest.

Larva
Larvae generally measure from 33 mm TL up to 30 cm which is the size of some untransformed adults (Petranka 1998). They have tail fins that extend forward to the insertion of the hindlimb. The gills are bushy and purplish to red. Ground color of larvae is light to dark brown. The larvae frequently have a yellow stripe behind the eye, and the toe tips are covered with dark, cornified skin (Nussbaum 1976). Some older larvae are mottled.

Larvae are mainly found in small to medium sized mountain streams (Nussbaum and Clothier 1973) and are most common in areas where stones and cobbles cover the stream bottom with little silt (Murphy and Hall 1981). Censuses by Murphy et al. (1981) showed that D. tenebrosus larvae are the dominant vertebrate fauna in terms of biomass in the Cascade Mountain Streams that were sampled.

Predators include fish, common garter snakes (Thamnophis sirtalis), northern water shrews (Sorex palustris), river otters (Lutra canadensis), weasels (Mustela) and other Dicamptodon (Nussbaum et al. 1983).

Trends and Threats
The primary threat to Dicamptodon is logging. Larvae are approximately four times more abundant in streams passing through unlogged versus logged stands (Corn and Bury 1989). In addition, larvae were present in all the unlogged streams, but were absent from 30% of logged streams. The species is far more abundant in unsilted versus heavily silted streams (Hawkins et al 1983). In high gradient streams populations may increase for the first five to seventeen years after logging due to increase in primary productivity (Murphy et al 1981). After canopy closure populations decline below numbers typical of old growth forests, due to increased siltation (Corn and Bury 1989). It may be difficult for adults to persist even in relatively good forest habitat if nearby logging ruins streams for the larvae. There has been a decline of D. tenebrosus populations in British Columbia due to habitat destruction by logging (Orchard 1992). Indeed this species is considered an endangered species in Canada (Munro 1993).

Relation to Humans
There is evidence that indicates that logging and other human disturbance is harmful to Dicamptodon, especially since the larvae depend on streams that are likely to be adversely affected by logging. It is rare to find adults in disturbed habitat, such as in clearings or on roads.

Possible reasons for amphibian decline

Habitat modification from deforestation, or logging related activities

Comments
Dicamptodon tenebrosus has until recently been included in D. ensatus, but recent genetic research has shown that the coastal Giant Salamander consists of two distinct species, D. tenebrosus to the north and D. ensatus to the south (Good 1989). These two species interbreed over a 4.7 km contact zone near Anchor Bay in Mendocino County, CA, but there is very little gene flow (Good 1989). There is a hybrid deficiency and little evidence of introgression outside the narrow hybrid zone (Petranka 1998).

This species is remarkable in their gregariousness, their formidable bite, their production of a “bark” (Stebbins 1951 1985), their large size, and consumption of mammals and other amphibians.

More work is necessary to determine the impacts that logging has had and the impacts that future logging could have on the abundance of this species.

See another account at californiaherps.com.

References

Childers J, Singh K, and Koo M. (2020). ''Natural History Note: Dicamptodon tenebrosus (Pacific Giant Salamander) Diet.'' Herpetological Review , 51(4), 806-807.

Corn, P. S. and Bury, R. B. (1989). ''Logging in Western Oregon: responses of headwater habitats and stream amphibians.'' Forest Ecology and Management, 29, 39-57.

Dethlefsen, E.S. (1948). ''A subterranean nest of the Pacific Giant Salamander, Dicamptodon ensatus (Eschscholtz).'' Wasmann Collector, 7, 81-84.

Diller, J. S. (1907). ''A salamander-snake fight.'' Science, 26, 907-908.

Good, D.A. (1989). "Hybridization and cryptic species in Dicamptodon (Caudata: Dicamptodontidae)." Evolution, 43, 728-744.

Hawkins, C. P., Murphy, M. L., Anderson, N. H., and Wilzbach, M. A. (1983). ''Density of fish and salamanders in relation to riparian canopy and physical habitat in streams of the northwestern United States.'' Canadian Journal of Fisheries and Aquatic Sciences, 40, 1173-1185.

Leonard, W.P., Brown, H.A., Jones, L.L.C., McAllister, K.R., and Storm, R.M. (1993). Amphibians of Washington and Oregon. Seattle Audubon, Seattle.

Munro, W. T. (1993). ''Designation of endangered species, subspecies and populations by COSEWIC.'' Our Living Legacy: Proceedings of a Symposium on Biological Diversity. M. A. Fenger, E. H. Miller, J. F. Johnson, and E. J. R. Williams, eds., Royal British Columbia Museum, Victoria, B.C., Canada, 213-217.

Murphy, M. L. and Hall, J. D. (1981). ''Varied effects of clear cut logging on predators and their habitat in small streams of the Cascade Mountains, Oregon.'' Canadian Journal of Fisheries and Aquatic Science, 38, 137-145.

Murphy, M. L., Hawkins, C. P., and Anderson, N. H. (1981). ''Effects of canopy modification and accumulated sediment on stream communities.'' Transactions of the American Fisheries Society, 110, 469-478.

Nussbaum, R. A. (1969). ''Nests and eggs of the Pacific Giant Salamander, Dicamptodon ensatus (Eschscholtz).'' Herpetologica, 25, 257-262.

Nussbaum, R. A. (1976). "Geographic variation and systematics of salamanders of the genus Dicamptodon Strauch (Ambystomatidae)." Miscellaneous Publications of the Museum of Zoology, University of Michigan, 149, 1-94.

Nussbaum, R. A., Brodie, E. D., Jr., and Storm, R. M. (1983). Amphibians and Reptiles of the Pacific Northwest. University of Idaho Press, Moscow, Idaho.

Nussbaum, R. A., and Clothier, G. W. (1973). ''Population structure, growth, and size of larval Dicamptodon ensatus (Eschscholtz).'' Northwest Science, 47, 218-227.

Orchard, S.A. (1992). ''Amphibian population declines in British Columbia.'' Declines in Canadian amphibian populations: designing a national monitoring strategy. C. A. Bishop nd K.E. Petit, eds., Canadian Wildlife Service, 10-13.

Petranka, J. W. (1998). Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C. and London.

Stebbins, R. C. (1985). A Field Guide to Western Reptiles and Amphibians. Houghton Mifflin, Boston.

Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.

Species Account Citation: AmphibiaWeb 2022 Dicamptodon tenebrosus: Pacific Giant Salamander <https://amphibiaweb.org/species/3867> University of California, Berkeley, CA, USA. Accessed Nov 2, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 2 Nov 2024.

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