Ministry of Environment
Pacific Giant Salamander
|Common Name:||Pacific Giant Salamander|
|Scientific Name:||Dicamptodon tenebrosus|
The Pacific Giant Salamander is one of the largest semi-aquatic salamanders in the United States and Canada. Terrestrial adults can reach a total length of 34 centimetres, while aquatic adults (neotenes) can reach up to 35 cm. These salamanders have a relatively large head, body, and legs. Their smooth skin usually has tan, gold, or grey mottling on top of a dark brown, reddish-brown, or grey background. However, some individuals lack the mottling and have uniform colouring. The underside is light brown or off-white. These salamander lack obvious costal grooves (indents along the body that look like ribs), but have dark hardened toe tips used for digging and climbing.
Larval Pacific Giant Salamanders are aquatic, with streamlined bodies adapted to life in fast-moving streams, unlike the pond-type larvae of other salamander species. They have short, bushy, purplish-red gills and a tail fin that extends only as far forward as the hind limbs. Their body is usually dark brown or grey, with some having similar mottling like the adults, and a pale underside. Larvae transform to the terrestrial form when they are approximately 9 to 16 cm in length, but some aquatic individuals are larger than 30 cm in total length. This latter group do not transform to the terrestrial form, but become neotenic, meaning that they become sexually mature while retaining larval characteristics like gills. These individuals remain aquatic their whole life. Larvae require several years of growth before they transform.
Pacific Giant Salamanders are found in a variety of habitats, but most live in the forest, near cool, clear, mountain streams. Mature and old-growth forests with plenty of litter, downed wood, and talus are preferred habitats, as terrestrial Pacific Giants spend most of their time under logs, rocks, and other debris, or in burrows; they are rarely seen crawling in the open.
Larvae and neotenes are found in small to medium-sized, cool, clear, fast-flowing creeks and streams that contain pools and suitable cover in the form of sand, boulders, logs, and overhanging banks. Larvae have also been found in lakes and ponds that do not contain salmonid fish (salmon and trout).
Little is known about the courtship and mating behaviour of the Pacific Giant Salamander. B.C. populations are believed to breed sometime between May and October. Males deposit a number of sperm packets, one or two of which are picked up by the female. Few nests have ever been found, but scientists think that females lay between 135 and 200 eggs in a variety of stream habitats such as in a stream bank, within a rock pile under a waterfall or on submerged logs. Each egg is attached individually to the substrate by a stalk that keeps it from being carried away by the current. Because females have been found near nests, it is assumed that they may tend the nest until the eggs hatch – which usually occurs after six months. The newly hatched larvae do not leave the nest chamber for another 3 to 4 months. Females lay eggs only once every two years.
It appears that in British Columbia, a high proportion of the adults within a Pacific Giant population are neotenic. On average, Pacific Giants take 2 to 4 years to reach sexual maturity, but B.C. populations may take 6 or more years. No one knows exactly how long Pacific Giant Salamanders can live, but data on other similar large, aquatic salamanders suggest that they may live up to 25 years.
Pacific Giant Salamanders have powerful jaws and voracious feeding habits. They feed on insects, slugs, snails, worms, shrews, mice, and amphibians. Larval salamanders eat a variety of aquatic organisms such as caddisflies, mayflies, stoneflies, beetles, worms, snails, small fish, and other larval amphibians of the same or different species, such as Tailed Frog tadpoles and Northwestern Salamander larvae.
Predators of Pacific Giants include salmonid fish, garter snakes, water shrews, River Otters, Raccoons, weasels, and other Pacific Giant Salamanders. Adults demonstrate aggressive behaviour when being attacked by predators, or when being territorial. They may bite, lash their tail, or exude noxious skin secretions from the top of their tail.
Pacific Giant Salamanders occur from extreme southwestern British Columbia (in the Chilliwack area) to northern California, from sea level to about 1000 metres, although some have been found as high as 2160 m.
In B.C., Pacific Giant salamanders are active from spring through fall, becoming dormant in winter. However, the terrestrial forms are hard to find, even in prime habitat, because they spend much of the active season in burrows or hidden under debris. Most of their above-ground activity occurs at night, especially warm nights with rainfall. It may be easier to detect aquatic Pacific Giants as they occur in streams year round, they can occur in high densities, and they have small home ranges (larvae have been recaptured within the same 10- to 20-m section of a stream across years).
The Pacific Giant Salamander is Red-listed in B.C., and was designated as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2000. The entire Canadian range of this species occurs within the Chilliwack Valley, in an area affected by logging and urban development. Survival of larvae in streams decreases when forest cover is removed and streams become silted, especially in low gradient streams where the water flow isn’t fast enough to flush out the silt. Larval densities may increase temporarily in higher gradient streams running through cutover areas due to the increased productivity. But, as the canopy closes in, densities drop below pre-harvest levels. Adults are rarely found in unforested areas such as clearcuts. Protection of suitable stream habitat and mature forest cover is vital to the survival of the Pacific Giant Salamander.
How We’re Helping
The Pacific Giant Salamander is protected under the British Columbia Wildlife Act. Under the Identified Wildlife Management Strategy of the Forest and Range Protection Act, Wildlife Habitat Areas can be established to protect important habitats. A recovery team of scientists and stakeholders is studying ways of further conserving the species.
You can help by learning more about these salamanders and other amphibians, and telling others about them. You can find out more about ways to protect habitat through programs such as Naturescape, Wetlandkeepers, and Wild BC. Be an ambassador for these salamanders in council meetings and other planning meetings! You can also help biologists learn more about the range, distribution, and habits of these and other amphibians by joining B.C. Frogwatch and observing salamander populations near you. The more we learn about salamanders in general, the better we can help the Pacific Giant Salamander.
- Pacific Giant Salamanders are one of the only salamanders capable of vocalization: when this salamander feels threatened, it has been known to produce a low-pitched growl or bark!
- These salamanders have also been known to climb trees and shrubs, up to heights of 2.5 m, using their hardened toe nails.
- Although larvae are considered to be fully aquatic, one gilled adult (neotene) was found on land 3 m from a small stream.
Photo © Wally Edwards. No reproduction or distribution without permission.