Northwestern Salamander

Ambystoma gracile adults may be either metamorphosed terrestrial salamanders or neotenic water-dwellers. Metamorphosed adults measure 14-22 cm in total length (Boundy and Balgooyen 1988). They are dark brown, gray, or black above and a lighter brown below. A glandular ridge forms a rounded top edge on the tail; the lower edge of the tail is sharp (Petranka 1998; Snyder 1963). Conspicuous oval parotoid glands sit immediately behind the eyes. The tail ridge appears rough due to concentrations of granular glands (Brodie and Gibson 1969). Both the parotoid and tail ridge glandular areas are pitted with openings of poison glands. Broad head, relatively small eyes. No tubercles on the underside of the feet (Stebbins 1985). Sometimes terrestrial individuals have small, irregular, whitish or yellowish spots and blotches on their dorsum (see Comments section below). Neotenic adults are strictly aquatic and retain gills. They may grow as large as 13 cm in snout-vent length and 26 cm in total length (Boundy and Balgooyen 1988). They are brownish to olive green in color, mottled with yellow and black. Distinct yellow spots sometimes sometimes dot the sides and tail. Ventral color varies from cream to pale or dark gray (Petranka 1998). The parotoid glands of untransformed adults are less prominent than those of transformed adults (Licht and Sever 1993). Both terrestrial and neotenic males become darker than females during the breeding season. Unmetamorphosed adult males have hypertrophied hindlimbs and feet, are less spotted, and have an enlarged glandular ridge on the tail (Snyder 1956). Larvae belong to the pond type, having long gills, long toes, and a long dorsal fin (Stebbins 1985). Hatchlings average about 8 mm in snout-vent length (Licht 1975). They have concentrated dark pigment along the base of the dorsal fin. Older larvae vary in color from dark brown to olive green or light yellow. They often have sooty blotches on the dorsum and may have yellow flecks or spots along the sides (Stebbins 1985).No morphological differences have been found to distinguish neotenic larvae from those that will transform (Snyder 1963). The spotted and unspotted varieties were originally designated as separate subspecies, with Ambystoma gracile decorticatum (British Columbia Salamander) possessing spots and Ambystoma gracile gracile (Brown Salamander) lacking spots. The spotted form occurs in the northern part of the range for A. gracile. A dividing line of 51 degrees north latitude was recognized between the two subspecies, with A. g. decorticatum occurring north of the line and A. g. gracile living to the south (Snyder 1963). Morphological characters such as the presence of 3 instead of 4 phalanges on the fourth toe, more prominent parotoid glands, and rows of 4 rather than 2 teeth on the prevomers have been used to differentiate between the unspotted A. g. gracile and the spotted A. g. decorticatum (Dunn 1944). However, Titus (1991) found that these distinctions do not always hold true and that genetic variation does not always correlate well with subspecies, and he suggested that A. gracile should not be split into subspecies. The specific epithet gracile is derived from the Latin term gracilis which means "slender" or "delicate." The subspecific name decorticatum istaken from the Latin de ("from") and cortex ("bark" or "cork"), meaning "like bark" (Snyder 1963). See another account at californiaherps.com (http://www.californiaherps.com/salamanders/pages/a.gracile.html).

Inhabits the northwest Pacific coast of North America. Found from southeastern Alaska on May Island south to the mouth of the Gualala River, Sonoma County, California. Occurs from sea level to timberline, but not east of the Cascade Divide. Range includes Vancouver Island in British Columbia and Cypress, Whidbey, Bainbridge, and Vashon Islands in Washington (Snyder 1963). The spotted forms occur in the northern portion of A. gracile's range (Petranka 1998; Snyder 1963; see Comments section below). Populations with neotenic adults are widespread, but the frequency of gilled adults increases with altitude such that adults at low and intermediate altitudes are almost all terrestrial, while adults at very high elevations are mostly neotenic (Eagleson 1976). Terrestrial adults live in mesic habitats ranging from grasslands to mesophytic forests. Terrestrial adults are mostly fossorial, and are usually active on the surface only during fall rains and spring migrations to their aquatic breeding sites. However, they can sometimes be found under logs and other surface debris outside of the breeding season (Petranka 1998; Efford and Mathias 1969).

The status of Ambystoma gracile populations is unknown (Blaustein et al. 1994). No declines are apparent in Canada (Weller and Green 1997). In the Cascade Mountains of Washington, Aubry and Hall (1991) found A. gracile to be far less abundant in young forests than in old-growth forests. However, Corn and Bury (1991) surveyed Western Oregon and found little correlation between salamander abundance and stand age, so it remains unclear whether A. gracile requires old growth forest to thrive. Clear-cutting, however, seems to render the habitat unsuitable; Corn and Bury found no salamanders on recent clear-cuts. Petranka (1998) suggests leaving a forest buffer of 200-250 m surrounding breeding sites used by terrestrial adults to preserve optimal environmental conditions for local populations. At an elevation of 183 m in the Cascade Mountains of Oregon, Blaustein et al. (1995) found A. gracile embryos to hatch with less mortality when shielded from UV-B radiation than when allowed to develop exposed to direct sunlight. This experiment was conducted in pond water 5-10 cm deep, which they claim is a common oviposition site for A. gracile in the Oregon Cascades. However, females often lay their eggs at greater depths and often in murky water, where they would be protected from UV-B, so the ecological relevance of Blaustein et al.'s experiment is controversial. Whether UV-B actually harms A. gracile populations is unknown (Petranka 1998). Because A. gracile breeds in relatively permanent bodies of water, Canadian populations may be unaffected by the increase in aridity predicted to occur in Canada due to global warming. However, decreased survival due to drying of breeding habitat may still occur (Ovaska 1997). A. gracile populations may be negatively affected by introduced predatory fish, such as trout and char. These fish can reduce or eliminate montane populations of ambystomatid salamanders (Burger 1950; Blair 1951; Sprules 1974; Taylor 1983). Tyler et al. (1998) tested the effects of trout on larvae of A. gracile and A. macrodactylum in artificial ponds and found that trout reduced both survivorship and average snout-vent length, and also narrowed the range of habitat use for larvae of both species. Trout also reduced average body mass of A. gracile larvae.

Terrestrial adults may defend themselves vigorously. When threatened, they may close their eyes, assume a head-butting position, and elevate the tail. They can secrete a sticky white poison from glands on the head, back, and tail, using head-butts and and tail-lashes to smear the poison onto the attacker (Stebbins 1985; Licht and Sever 1993). A ticking sound may accompany this defense (Licht 1973). Larvae and neotenic adults flee attack from natural predators such as trout and beetle larvae (Nussbaum et al. 1983). This species breeds in permanent or semi-permanent waters, ranging from small, shallow ponds to large, deep lakes, and sometimes including side pools of slow streams. Breeding takes place in the spring; the exact timing varies with latitude and elevation (Brown 1976; Licht 1969; Licht 1975). Mating pairs of A. gracile enact an elaborate courtship ritual that seems to vary between different regions. Fertilization is internal; the female picks up a spermatophore deposited by the male (Licht 1969; Knudsen 1960). Length of embryonic development is positively correlated with water temperature and varies from 2-9 weeks (Petranka 1998). Most larvae in lowland populations transform when 12-14 months old, in the spring following hatching (Eagleson 1976; Licht 1975). Larvae at high elevations transform in their third year (Eagleson 1976). Hatchlings feed on zooplankton; older larvae eat a variety of prey, including annelids, mollusks, insect larvae, copepods, ostracods, and flatworms (Licht 1975; Efford and Tsumura 1973).

The poison secreted by terrestrial Northwestern Salamanders may irritate the skin of some people (Stebbins 1985).

Maximum longevity: 10.2 years (captivity)

Ambystoma gracile generally live five years.

Average lifespan
Status: wild: 5 years.

Average lifespan
Status: captivity: 10.2 years.

Studies have shown that predation on larval salanders can drive a population towards extirpation. It was found that predatory trout in breeding locations has reduced both average snout-vent length and recruitment, which has caused a narrowing of local population densities. The presence of trout has also correlated with a decrease in total body mass of the larvae by driving them into sub-optimal habitats to forage.

Known Predators:

• trout Salmoniformes
• beetle larvae Coleoptera

Aquatic adult Ambystoma gracile grow to approximately 13 cm in snout-vent length and 26 cm in total length. They typically exhibit olive-green or brownish colorations. The ventral coloration ranges from dark gray to pale white. Larvae have long, thick gills, an extended dorsal fin, and relatively long toes.

Terrestrial adults are about 14-22 cm in total length. Often, they have blotches on the dorsum and may have yellow flecks along the sides. These salamanders have a smooth brown or dark brown dorsal coloration and light brown ventral skin. There is an area of swelling behind each eye due to the parotoid glands. This feature is uncharacteristic of other Ambystomids, and resembles the condition on old world salamanders of the genus Salamandra. A glandular ridge forms a rounded tip on the dorsal tail; the distal portion of the tail is sharply tapered. In some instances, terrestrial individuals have irregular, small, light-colored blotches on the dorsum. Both aquatic and terrestrial males become darker than females during the breeding season. Unmetamophosed adult males have hypertrophied feet and hind limbs, less spots, and an enlarged glandular ridge on the tail.

Range length: 14 to 22 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; poisonous

Sexual Dimorphism: sexes alike

These salamanders inhabit humid sites within dense forests and open grasslands. Adults are often found beneath rotting logs, leaf litter, and debris along stream banks. As members of the "mole salamander" genus Ambystoma, most of their time is spent underground. They are most frequently seen during fall rains and spring migrations to their aquatic breeding sites, which are usually temporary ponds with no fish presence. The larvae also reside in these ponds until metamorphosing.

Range elevation: 0 to 3110 m.

Habitat Regions: temperate

Terrestrial Biomes: forest

Aquatic Biomes: lakes and ponds

Ambystoma gracile range from southeastern Alaska along the Pacific coasts of British Columbia, Washington, Oregon, Vancouver Island, to northern California (Mendocino).

Biogeographic Regions: nearctic (Native )

In lowland populations of British Columbia, these salamanders catch and consume soft-bodied invertebrates such as annelids, mollusks, cladocerans, ostracods, amphipods, anostracans, isopods, copepods, mites, dipterans, and a variety of other insect larvae.

Larval salamanders consume aquatic annelids, aquatic arthropods, and small mollusks.

Animal Foods: eggs; insects; terrestrial non-insect arthropods; mollusks; terrestrial worms; aquatic or marine worms; aquatic crustaceans; zooplankton

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods, Molluscivore , Vermivore); planktivore

In some areas, juvenile A. gracile provide food to aquatic predators. On land, they also function as important members of the trophic pyramid by consuming invertebrates and in turn are preyed upon by larger organisms.

This species can also serve as an indicator of environmental degradation. Salamander eggs can only hatch in clean, fresh water with little UV radiation. A drastic decrease in salamander numbers can signal a change has occurred within the ecosystem.

Aside from their contribution to the biodiversity of northwest US forests, A. gracile is not a species of economic importance.

Ambystoma gracile do not negatively impact humans. If, by chance, an animal was consumed by a person, its poisonous skin secretions would likely cause sickness.

Negative Impacts: injures humans (poisonous )

Embryonic periods typically last 2-9 weeks, depending on ambient temperatures. After emerging, hatchlings experience rapid growth due to an abundance of accumulated food items in the pond. Larvae in lowland populations tend to grow faster than those at higher elevations. Young A. gracile measure 50-90 mm after 1 year. These salamanders transform the following spring at the ages of 12-14 months. Metamorphosis generally begins at 50 mm total length. Some A. gracile reproduce while still exhibiting larval features, such as gills. These salamanders are known as neotenic. The majority of salamanders, however, does not stay in water and becomes sexually mature during their second year of life on land.

Development - Life Cycle: neotenic/paedomorphic; metamorphosis

Road development is a major threat to the breeding migrations of salamanders. They fragment the habitat and put the animals in danger of car mortality. Moreover, research suggests that A. gracile prefer to inhabit old-growth forests, which are heavily harvested in many areas. Placing a forest buffer of 200-250 m around breeding sites used by terrestrial adults will help in preserving current populations. Finally, the introduction of trout to a water system previously devoid of large predators can severely weaken the salamander population in the surrounding area.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

When molested these salamanders may give off a ticking sound and assume a defensive posture. As nocturnal hunters, much of the salamanders' perception of the world relies on smell. Airborne scents are picked up with the olfactory system. After a general direction is identified, the vomeronasal system tracks minute scents on the ground, leading the animal towards its target.

Communication Channels: visual ; tactile ; chemical

Limb regeneration is a phenomenon that occurs in this species. Tissue in the remnants of the limb regenerate nerve fibers, and the new limb bud slowly emerges and forms.

Ambystoma gracile is commonly referred to as the northwestern salamander, or is divided into two subspecies, the brown salamander, Ambystoma gracile gracile (found in the southern portion of the range), and the British Columbia salamander, Ambystoma gracile decorticatum (found in the northern range).

Breeding occurs once yearly. Pairs are always monogamous in that once a female takes a spermatophore inside her body, the eggs are fertilized. However, new mates are selected randomly every year and selection depends on the performance of a mating ritual.

Mating System: monogamous

Breeding takes place in both permanent and semipermanent bodies of water. Migration to these areas occurs during the transition from Winter to Spring (January-April, depending on latitude).

Upon contact with a potential mate, the male salamander dorsally mounts the female and stimulates her with his chin and tail. Afterwards, the male swims a short distance away and deposits a spermatophore package (a solid, airtight conglomeration of sperm). If breeding interest still exists, the female will follow. The male salamander then stimulates the female in a behavior similar to a tickle as she inserts the spermataphore into her cloaca to fertilize her eggs. It should also be noted that other mating rituals have been observed, including stereotyped attempts at insertion of the spermatophore by the male. Always, this behavior fails, and the spermatophore is picked up by the female and inserted into the cloaca.

Eggs are deposited between January and May and are typically attached to rooted aquatic vegetation. The salamander larvae emerge after approximately one month, but may take as many as nine weeks to hatch. Hatchlings measure 8 mm in snout-vent length.

Breeding interval: Once Yearly

Breeding season: January-May (dependent on latitude)

Range number of offspring: 40 to 270.

Average number of offspring: 150.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous ; delayed fertilization

Eggs are typically deposited in a habitat devoid of predatory fish. All of the salamanders evacuate the pond shortly after the breeding season, leaving the eggs in the water until hatching.

Parental Investment: no parental involvement; pre-fertilization (Provisioning)

The northwestern salamander (Ambystoma gracile) is a species of mole salamander that inhabits the northwest Pacific coast of North America. These fairly large salamanders grow to 8.7 in (220 mm) in length. It is found from southeastern Alaska on May Island, through Washington and Oregon south to the mouth of the Gualala River, Sonoma County, California. It occurs from sea level to the timberline, but not east of the Cascade Divide. Its range includes Vancouver Island in British Columbia and The San Juan Islands, Cypress, Whidbey, Bainbridge, and Vashon Islands in Washington.