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Cope's Giant Salamander
Dicamptodon copei
California Giant Salamander
Dicamptodon ensatus
  (Eschscholtz, 1833)
Pacific Giant Salamander
Dicamptodon tenebrosus
  Owner:   C. Michael Hogan    

California Giant Salamander, Copeland Creek, California
California Giant Salamander
Dicamptodon ensatus

C. Michael Hogan PhD
September 12, 2008

D.ensatus is one of the most massive terrestrial salamanders in North America, with robust body and head. The limited North Coast Range distribution of this California endemic places the species in a near threatened status. The California Giant Salamander is one of the few salamanders that is able to vocalize, especially when attacked as a mechanism of frightening off predators.



DISTRIBUTION AND PHYLOGENY
The California Giant Salamander occurs in the North Coast Range of California from Point Arena in Mendocino County south to Marin and Napa Counties and disjunctively in coastal areas of San Mateo and Santa Cruz Counties. A further disjunct population occurs to the south in Big Sur (Nussbaum). Populations have declined in the past 150 years due to conversion of large tracts of land for urban and agricultural usage; to deforestation and due to human alteration of forest types. A preferred habitat type are cool headwaters of streams within the California North Coast Ranges, where species such as California Black Oak and California Bay Laurel provide shade and temperature moderation for D.ensatus. (Hogan) The headwaters of Copeland Creek in the heavily forested Fairfield Osborn Preserve are a prototypical example of this habitat.

D. ensatus is the southernmost taxon of four closely related species. Earlier taxonomy identified D. tenebrosus (Coastal Giant Salamander) and D. aterrimus (Idaho Giant Salamander) within the same taxon as D. ensatus, until DNA analysis made it clear that tenebrosus (coastally distributed from Point Arena to British Columbia) and aterrimus (occurring in Idaho and Montana) are genetically distinct from the (Monterey County to Point Arena) coastal D. ensatus. D. copei (Cope's Giant Salamander), found on the Olympic Peninsula of Washington, is morphologically similar to the foregoing taxa.



MORPHOLOGY
Mature D. ensatus extends six to 17 cm from snout to vent, with a tail of nine to 14 cm. It has sturdy limbs and a light brownish red back with a superimposed dorsal and flanking copper-colored marbling, but a belly which is pale brown to yellowish-white. This salamander has four toes on each front foot, and five toes on the hind feet. have a broad head with a shovel-like snout and a fold of skin across the throat called the gular fold. The eye structures are unremarkable except for a dotted iris and a largish black pupil. The adult head manifests a shovel-like snout and a gular fold The venter is pale yellow grading to white, typically without markings. Transformed adults have 12 to13 somewhat indistinct costal grooves, and exhibit a flattened tail with the broader aspect facing sideways. Neoteny is common in this species; with gilled sexually mature individuals sometimes being more numerous than transformed adults. The drab red gill structures are abbreviated and bushy. Stream dwelling larvae have tail fins, sometimes with black mottling, that do not extend forward of the rear limbs.



BEHAVIOR
D. ensatus feeds nocturnally on invertebrates as well as small vertebrates including amphibia, mammalia and reptilia. Aquatic larvae of D. ensatus are thought to prey upon small aquatic invertebrates and fish fry. The larvae are also notably voracious, consuming tadpoles, insects and even cannabalize smaller larvae of their own species. Transformed individuals forage among leaf litter and detritus on rainy nights. Larvae are often more numerous than transformed adults, and they thrive in low turbidity, cool waters; Typically they are found beneath stones and leaf detritus in stream pools, often near banks or next to exposed boulders. To defend against predators, this salamander will bite, thrash about and emit odorous chemicals from glands on the dorsal tail. D. ensatus is one of the few salamanders which is capable of vocalizing. (Behler)

Sexually mature adults migrate to surface waters for breeding when the rainy season begins. Females attain sexual maturity at age five or six and are only able to reproduce once every other year. The female deposits from 80 to 200 eggs in a clandestine subterranean or underwater nest. Eggs hatch in five to ten weeks, with the female guarding from predators. Once the larvae hatch, they typically transform by late summer.



CONSERVATION
Because of the limited occurrence of this species, an areal extent less than 20,000 square kilometers, this species is categorized as Near Threatened. (Bury) Urban development, stream siltation, deforestation and grazing (particularly for livestock allowed to intrude into riparian zones) are the principal threat mechanisms. Bury has identified a list of eleven unmet needs applicable to the California Giant Salamander related to policy, research and habitat protection, the most substantive item being the need for provision of corridors. Expanded protection, particularly of riparian corridors, is significant in that this region is faced with a rapidly expanding human population, with some of the local governments not having demonstrated strength in conservation planning.



REFERENCES

* R.A. Nussbaum (1976). Geographic variation and systematics of salamanders of the genus Dicamptodon Strauch (Ambystomatidae). University of Michigan, Museum of Zoology, Publication. 149:1-94.
* C.Michael Hogan (2008) California Black Oak: Quercus kelloggii, GlobalTwitcher, ed. N. Stromberg
* John H. Behler (1996) Field guide to North American reptiles and amphibians, National Audubon Society, Chanticleer Press ISBN 0-394-50824-6
* J.W. Petranka (1998) Salamanders of the United States and Canada, Smithsonian Institution Press. Washington, D.C.
* R.B.Bury (2005) Dicamptodon ensatus {Good, 1989): California Giant Salamander. Status and Conservation of U.S. Amphibians. Vol. 2: Species Accounts. M.J.Lannoo,,ed. Univ of California Press,. Berkeley, California.