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Dicamptodon tenebrosusCoastal Giant Salamander(Also: Pacific Giant Salamander)

By Mike Leighton

Geographic Range

Pacific giant salamanders occupy the coastal areas of British Colombia, Oregon, Washington, and northern California. In British Colombia, these salamanders are only found in the extreme southwest region, south of the Fraser valley and in the Chilliwack district. (Bishop, 1947; Carl, 1959)

Habitat

Pacific giant salamanders live in small to midsized streams. They also occupy moist, riverside forests. The type of stream bed they prefer is composed of large gravel to small boulders having some large logs in them with very little silt on the bottom of the stream. During rainy periods this species may also be found under forest litter such as leaves and small branches. This species can be found at elevations from sea level to 1830 m. (Corkran and Thoms, 2006)

  • Aquatic Biomes
  • rivers and streams
  • Range elevation
    sea level to 1830 m
    to 6003.94 ft

Physical Description

Pacific giant salamanders are the largest terrestrial salamander in the Pacific Northwest and are one of the largest terrestrial salamanders in the world. Adults of this species may exhibit neoteny and retain gills to live a more aquatic lifestyle, or may metamorphose completely and live terrestrially. Gilled, aquatic adults are common in more coastal populations and in those of British Columbia.

The dorsal surface of most adults is dark brown to nearly black and is covered with light brown spotting or marbling, though coloration varies between individuals and populations. The ventral side is unmarked and white or pale in color. Young salamanders have bright golden marbling that becomes more diffuse and more conspicuous with age. The pattern may fade in very old adults but they usually retain some spotting on the head. Larval salamanders metamorphosize when they reach 92 to 166 mm in length.

Pacific giant salamanders have moderately broad heads, short blunt snouts, and medium sized eyes with brass-freckled irises. There is a guar fold; but there are no parotoid glands present in this species of salamander. They have large strong legs with no webbing or tubercles on the soles of their feet. They have 12 rather indistinct costal grooves on each side of the body. The tail makes up two fifths of the body length. The tail is stout and laterally compressed, and males of the species have slightly longer tails than the females. Adults measure 6.25 to 17 cm snout-vent length (SVL) and may reach 34 cm in total length. Adult mass ranges from 22 to 114 g.

In addition, Pacific giant salamanders have a basal metabolic rate of 31.2 +or- 4.3 at a temperature of 15 degrees Celsius. The value for basal metabolic rate is temperature dependent. (Green and Campbell, 1984; Petranka, 1998; Wood, 1972)

  • Sexual Dimorphism
  • male larger
  • Range mass
    22 to 114 g
    0.78 to 4.02 oz
  • Range length
    34 (high) cm
    13.39 (high) in
  • Range basal metabolic rate
    20.7 to 63.3 cm3.O2/g/hr

Development

Little is actually known about the development of Pacific giant salamanders. It is known that environmental conditions (such as the cold temperature of preferred streams) affect the growth and survival of the larvae. After they are laid, the eggs may take up to 7 months to hatch. Larvae are 3 cm long upon hatching and feature large yolk sacs that will sustain them for 2 to 4 months. At this point, the young are about 40 cm in length, and can begin to hunt their own prey. Metamorphosis begins 18 to 24 months after hatching, when the young are 92 to 166 mm in length.

Pacific giant salamanders exhibit slow growth rates and do not reach sexual maturity until 5 or 6 years of age. Adults of this species may be terrestrial or aquatic; the aquatic being neotenes which retain many larval characteristics like external gills. Neoteny seems to be more prevalent in certain, more coastal populations, specifically, British Colombia salamanders are nearly all neotenes. ("Wildlife at risk in British Colombia: Pacific giant salamander", 1993; Lannoo, 2005; Sagar, et al., 2007)

Reproduction

Very little information is available about the mating system for Pacific giant salamanders. Courtship occurs from spring to fall, and reproductively mature, terrestrial females will migrate to streams to oviposit. Field observations have suggested that the courtship ritual occurs terrestrially in crevices under rocks and logs, however, the courtship behavior has not been directly observed. (Petranka, 1998)

When it is time for the females to ovipost they migrate from upland habitats to streams. It is unknown if these salamanders breed yearly as the females have a significant parental investment of guarding her eggs for up to 7 months. Most females appear to oviposit during early to mid May then they guard their eggs until hatching. The few nests that have been discovered have been in subterranean habitats in running water. These salamanders have one of the longest incubation periods of all salamanders. Hatchlings appear in December and January about 6 to 7 months after oviposition. It takes 5 to 6 years for Pacific giant salamanders to reach sexual maturity. ("Wildlife at risk in British Colombia: Pacific giant salamander", 1993; Blood, et al., 1993; Lannoo, 2005; Petranka, 1998)

  • Breeding interval
    The breeding interval for Pacific giant salamanders is unknown.
  • Breeding season
    Pacific giant salamanders breed from spring through fall, with high altitude populations breeding later.
  • Range number of offspring
    83 to 146
  • Range time to hatching
    6 to 7 months
  • Range age at sexual or reproductive maturity (female)
    5 to 6 years
  • Range age at sexual or reproductive maturity (male)
    5 to 6 years

After mating terrestrially, female Pacific giant salamanders will migrate to fast-flowing streams to lay their eggs. The females will guard the aquatic clutches until the young hatch after 6 or 7 months. Cannibalism is well documented among the males of the species, which may explain why the female is in attendance. (Nussbaum, 1969; Nussbaum, 1969)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Nothing is yet known about the lifespan of Pacific giant salamanders however, other species of aquatic salamander are known to be long-lived. Given that the young take 5 to 6 years to reach reproductive maturity, they are likely a long-lived species as well. (Lannoo, 2005)

Behavior

The newly metamorphosed and sometimes paedomorphic individuals move out of streams during rainy, wet periods. Some will remain in the vicinity of the streams while others go to higher ground. Both the larvae and adults seek refuge from temperature extremes such as in winter during freezing temperatures.

Pacific giant salamanders are mostly nocturnal, though may be active during the early morning hours as well. Female salamanders will perform migrations to suitable streams for oviposition, but currently this seems to be the only migrational behavior for this species. As most salamanders live within 50 m of a stream, these migrations are not significant and the species is considered sedentary.

From what is known of these salamanders, they lead largely solitary lives but individuals will come together to breed. They exhibit very territorial behaviors and will forcefully guard burrows from intruders. (Lannoo, 2005)

  • Range territory size
    3,047 to 5,196 m^2

Home Range

It has been documented that the home range size of this species is between 3,047 and 5,196 metres squared. ("Wildlife at risk in British Colombia: Pacific giant salamander", 1993; Lannoo, 2005)

Communication and Perception

When disturbed by predators Pacific giant salamanders will emit a "bark". When approached by a predator, individuals strongly arch their bodies and may thrash their tails to threaten the predator. They can also secrete a noxious substance from their tails to ward off predators. The adults of this species will also head butt and bite viciously. They often produce a rattling or growling sound while snapping their jaws and lashing their tail. Little information exists about the communication between members of this species. (Lannoo, 2005; Petranka, 1998)

Food Habits

The larvae of the species will consume a variety of invertebrate prey in a wide range of sizes. They will consume insect larvae and adults, amphipods, ostracods, termatoes, mollusks, and crayfish. Larger larvae will prey on some salmonids, sculpins, and salamanders. Adult diets are dominated numerically by aquatic organisms but they consume a higher volume of terrestrial prey. Terrestrial adults emerge from logs and other surface cover on rainy nights and forage the forest floor. Individuals of this species may forage one and a half to two meters above the ground on tree trunks. Large terrestrial members of the species can handle eating small mammals such as mice and shrews or even snakes. Pacific giant salamanders are sit and wait predators who quickly lunge short distances in order to obtain prey. (Lannoo, 2005; Parker, 1994; Petranka, 1998)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • mammals
  • amphibians
  • reptiles
  • fish
  • eggs
  • insects
  • other marine invertebrates

Predation

Natural predators of Pacific giant salamanders are weasels, river otters, water shrews, garter snakes (Thamnophis genus), salmonids and conspecifics. When approached by predators salamanders employ a variety of anti-predator adaptations. These include tail lashing, biting, arching of the back, and skin secretions. They are also known to emit a warning bark. Their black and brown marbled coloration is cryptic in their terrestrial and aquatic habitats. (Lannoo, 2005)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators
    • Weasels
    • Garter snakes (Thamnophis genus)
    • Salmonids
    • Pacific giant salamanders (dicamptodon tenebrosus)
    • Water shrews
    • River otters

Ecosystem Roles

Pacific giant salamanders likely impact prey populations of aquatic and terrestrial vertebrates, as well as aquatic invertebrates. High frequency of small mammals in the diet of large, terrestrial adults suggests that these salamanders may play a role in structuring the shrew and mice communities. Parasitic helminths have been found in this species. (Lannoo, 2005; Petranka, 1998)

Commensal/Parasitic Species
  • Helminths

Economic Importance for Humans: Positive

Pacific giant salamanders are predators of small mammals including mice, which may be of economic benefit to humans, as mice have become a prevalent pest for farms, industries and homes. (Petranka, 1998; Pimentel, et al., 2005)

Economic Importance for Humans: Negative

There are no known adverse effects of dicamptodon tenebrosus on humans.

Conservation Status

In the United states, Pacific giant salamanders are considered of "least concern" to the IUCN Red List and are not protected federally or by CITES. Populations are currently stable but have become fragmented as a result of forestry in their habitats. However, several studies have indicated that populations of Pacific giant salamanders decline after the logging of old growth forests. Both terrestrial and aquatic populations are affected by logging as their habitats suffer from decreased canopy cover which likely alters temperature, moisture, and degree of siltation. Studies have shown that this species is far more abundant in un-silted streams compared to heavily silted streams.

In British Colombia however, Pacific giant salamanders are considered nationally imperiled and are included in the Canada Species at Risk Act. They are considered important in conserving the biological diversity of native ecosystems in the region. To address these concerns, the British Colombia Ministry of Environment created a management strategy in April 2010 to ensure a self-sustaining population in southwest British Colombia. ("Recovery strategy for the Pacific Giant Salamander (Dicamptodon tenebrosus) in British Columbia", 2010; Petranka, 1998)

Other Comments

Pacific giant salamanders are known to hybridize with Californian giant salamanders in a few of the streams of southern Medocrine County in California. They are known to be sympatric with Cope giant salamanders across the range of Cope giant salamanders. (Lannoo, 2005)

Contributors

Mike Leighton (author), University of Alberta, Augustana Campus, Doris Audet (editor), University of Alberta, Augustana Campus, Rachelle Sterling (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

Pacific Giant Salamander Recovery Team. Recovery strategy for the Pacific Giant Salamander (Dicamptodon tenebrosus) in British Columbia. Victoria, British Colombia: B.C. Ministry of Environment. 2010. Accessed February 02, 2011 at http://www.env.gov.bc.ca/wld/documents/recovery/rcvrystrat/pacific_giant_salamander_rcvry_strat26Apr2010.pdf.

Province of British Columbia: Ministry of Environment, Lands and Parks. Wildlife at risk in British Colombia: Pacific giant salamander. Victoria, British Colombia: Ministry of Environment, Lands and Parks. 1993. Accessed February 02, 2011 at http://www.env.gov.bc.ca/wld/documents/salamander.pdf.

Bishop, S. 1947. Handbook of Salamanders. Ithaca, New York, USA: Cornell University Press.

Blood, D., M. Hames, R. Pawlas. 1993. "Pacific Giant Salamander" (On-line pdf). Accessed November 18, 2009 at http://www.lfpsf.org/pacific_giant_salamander.pdf.

Carl, G. 1959. The Amphibians of British Columbia. Victoria British Columbia: British Columbia Department of Education.

Corkran, C., C. Thoms. 2006. Amphibians of Oregon, Washington, and British Columbia. Edmonton, Alberta, Canada: Lone Pine.

Green, D., R. Campbell. 1984. The Amphibians of British Columbia. Victoria British Columbia: British Columbia Provincal Museum.

Lannoo, M. 2005. Amphibian Declines: The Conservation Status of United States Species. Berkley: University of California Press.

Mankiwn, N., N. Rowe, R. Kneebone, K. McKenzie. 2008. Princliples of microeconomics fourth edition. Toronto: Thompson Nelson.

Nussbaum, R. 1969. Nests and Eggs of the Pacific Giant Salamander, Dicamptodon ensatus. Herpetologica, 25: 257-262.

Parker, M. 1994. Feeding Ecology of Stream-Dwelling Pacific Giant Salamander Larvae (Dicamptodon tenebrosus). Copeia, 3: 705-718.

Petranka, J. 1998. Salamanders of the United States and Canada. Washington: Smithsonian Insitution.

Pimentel, D., R. Zuniga, D. Morrison. 2005. Update on the environmental and economic costs associated with alien invasive species in the united states. Ecological economics, 52: 273-288.

Sagar, J., D. Olson, R. Schmitz. 2007. Survival and Growth of Larval Coastal Giant Salamanders (Dicamptodon tenebrosus) in Streams in the Oregon Coast Range. Copeia, 1: 123-130.

Wood, S. 1972. Metabolic Rate of Larval and Adult Pacific Giant Salamanders, Dicamptodon ensatus. Copeia, 1: 177-179.

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