Northwestern salamander (Ambystoma gracile)

Physical description

A large, stocky, brown salamander with a rounded snout, prominent parotoid glands (poison glands) behind the eyes, distinct costal grooves and a laterally compressed tail with a glandular ridge on the dorsal surface; the conspicuous parotoid glands and glandular tail ridge distinguish this species from all other Washington salamanders. Adults are 3.14 to 3.5 inches snout to vent length, 5.5 to 8.7 inches total length. During the breeding season, males have conspicuously swollen vent lobes and females have a rounded protuberance around the vent. 

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Photo by W.P. Leonard, Copyright

Larvae 

Larvae are typical pond type with large gills and a high tail fin. Hatchlings have translucent skin with dark spots and yellow bellies. Rod-like extensions on the head, called balancers, are present. Small larvae are typically olive or brown in color, usually with dark spots or mottling. The gill filaments are closely packed on the gill stalks and are similar in length. Hind limbs develop after the larvae grow to about 1 inch in total length.

Large larvae (greater than 2 inches snout to vent length), are olive to brown in coloration often with dark spots or mottling. They develop huge gills with thick gill stalks, robust legs and glandular patches on the head and tail. The glandular patches are less conspicuous than on transformed juvenile and adults. The belly coloration tends to be cream, gray or brown depending on the size and stage.

Large larvae and gilled adults (neotenes) can grow larger than 3 inches total length. The number of gill rakers on the anterior arch of the third gill arch number less than 13 (range 7 to 10). 

Newt larvae differ in having eyes on the margin of the head, a snout that narrows in front of the eyes, a faint horizontal stripe from the snout through the eye, and one or two distinct rows of white spots down the back and sides.

No obvious external characteristics distinguish small long-toed salamander larvae (less one inch total length) from northwestern salamander larvae. With experience, one can recognize subtle differences in the gills, the way the larvae hold their gills, head size, head shape and coloration. In general, long-toed salamander larvae have gill filaments that are “ragged” and uneven in length. The top gill filament is usually longer than the rest of the gill filaments on the stalk. The skin coloration tends to remain somewhat translucent and is less likely to have distinct spotting. Hind leg development starts before larvae reach one inch total length and larvae remain relatively small (rarely exceed 80 mm total length) and never develop huge gills or robust legs.

The range of the northwestern salamander overlaps with the tiger salamander only in southwestern Klickitat County where one tiger salamander specimen was collected in the 1930s. The location is isolated from the rest of the tiger salamander range and the exact collection site is unknown.

Larvae of these two species are similar in general appearance but large northwestern salamanders usually have glandular patches on the head and tail. Gill counts can be used to confirm species of larvae that lack glandular patches. Tiger salamanders have more than 13 gill rakers on the anterior surface of the third gill arch whereas northwestern salamanders have fewer.

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Photo by WDFW

Eggs

In Washington, only northwestern salamanders have large globular egg masses that are firm to the touch. The egg masses are attached to sturdy plant stalks and twigs. The egg masses may be round or elongate and are about the size of an orange measuring 3.15 to 6 inches in diameter. Ova are light brown at one pole and cream colored at the other. When first laid the gel around the eggs has a white tint. Fully expanded egg masses exposed to sunlight develop a distinct greenish tinge from symbiotic algae that grow in the inner jelly layer.

In Washington, only northwestern salamanders are distinguished as having large globular egg masses that are firm to the touch.

For more details about northwestern salamanders, see the Washington Herp Atlas. 

Ecology and life history

Mesic forests are the main terrestrial habitat occupied by this species. One Washington study found them to be less abundant in young forest when compared to older forests, but other studies have found little correlation of abundance with stand age. Northwestern salamanders use permanent water bodies for breeding. Breeding habitats include ponds, wetlands, lakes, road ditches and slow-moving creeks. 

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Photo by S. Anderson, National Park Service

Larvae and gilled adults can persist in the presence of introduced trout but may be forced to use sub-optimal habitats and to forage at night. This may result in reduced size and recruitment. Anecdotal observations suggest that large populations of introduced warm-water fish, such as largemouth bass, may deter salamander breeding.

Metamorphosed forms spend most of their lives in the subterranean environment and are rarely seen except for spring migrations to breeding ponds. Surface activity is nocturnal. They shelter under woody debris, ground litter, and accumulated duff below sword ferns.

Breeding starts in late January through March at lower elevations (less 1000 feet), later at higher elevations. The embryos take one to two months to develop. The empty gelatinous egg masses persist for weeks to months after hatching is complete.

Larvae may transform in their second year around 2 inches snout to vent length (3 to 3.5 inches total length) or may remain permanently aquatic. Observations at some sites suggest that larva may transform in the first year under certain conditions (pond drying).

Ponds often contain many different size classes of larvae, including gilled adults (neotenes).

Populations are highly polymorphic (occurring in different forms) consisting of populations that always transform, populations that never transform, and populations that metamorphose depending on environmental conditions Gilled adults tend to dominate high-elevation populations.

Geographic range

In Washington, northwestern salamanders occur primarily west of the Cascade Crest in the Pacific Coast, Puget Trough and West Cascades Ecoregions. They also occur east of the Cascade Crest in some areas of the East Cascades Ecoregion.

This map from the Washington Herp Atlas illustrates the distribution of northwestern salamander in Washington based on records in the WDFW database as of 2016. If you see this species in areas that are not indicated on the map or have more recent observations (less than 10 years), please share your observation using the WDFW wildlife reporting form.  

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For a map of range-wide distribution and conservation status of this species, check out NatureServe Explorer and the International Union for Conservation of Nature Redlist.