Rhyacotriton olympicus

Rhyacotriton olympicus has a snout-vent length between 4.1 and 6.2 cm (Stebbins 1985) and tends to be the largest species of Rhyacotriton (Good and Wake 1992). Gaige (1917) originally described R. olympicus with "skin shining, closely pitted, without tubercles". The salamander has 14 costal grooves, one median dorsal groove, and five toes on short, well-developed limbs which fail to meet when adpressed. Toes are distinct and rounded, the third toe being longest, with the second and fourth and first and fifth being equal in length. The snout is rounded, head small and depressed, with nostrils near the end of the snout. The eyes are prominent, and eyelids appear swollen. The tail is shorter than snout-vent length, with strong lateralcompression and keeled above, ending in an obtuse point. The vent is a longitudinal slit with a distinct transverse groove at the posterior end (Gaige 1917). Males have distinct squarish, glandular vent lobes, a trait unique among salamanders (Stebbins 1985; Sever 1988). Stebbins and Lowe (1951) and Good and Wake (1992) described adult coloration as uniformly dark chocolate brown above with the dark dorsal coloration ending distinctly along the side in a wavy line. Ventrally, the salamander is orange yellow with mottling of brownish in the gular area, and with well defined dark spots on the underside of the body and tail.

Stebbins and Lowe (1951) described the aquatic larvae as similar to adults in coloration, but with a more mottled appearance. Very young larvae may have whitish venters, but larger larvae are more similar to adult in ventral coloration. They have short gills and adult proportions and are of the stream larva type(Stebbins 1985).

Rhyacotriton was first described by Gaige (1917) as a member of the hynobiid genus Ranodon. Dunn (1920) placed it in the family Ambystomatidae and it was subsequently placed in its own subfamily, Rhyacitritoninae by Tihen (1958). Regal (1966) placed Rhyacotriton in the subfamily Dicamptodontinae, which was elevated to the family Dicamptodontidae by Edwards (1976). The genus was finally placed in its own family by Good and Wake (1992). Considered to contain only one species, R. olympicus, until the work of Good et al. (1987), thefamily now contains four species , R. olympicus, R. variegatus, R. kezeri, and R. cascadae(Good and Wake 1992).

Rhyacotriton olympicus is restricted to the Pacific Northwest of the United States, specifically the Olympic Peninsula in Callam, Grays Harbor, Jefferson, and Mason counties Washington (Good and Wake 1992). The preferred habitat is along the water-washed or moss-covered edges of well-shaded, fast-flowing permanent streams (Good and Wake 1992; Stebbins and Lowe 1951), although the preferred resting habitat tends to be relatively slow-moving waters(Stebbins and Lowe 1951). There is usually a good leaf canopy, with the streamside being characterized by abundant vegetation, moss and a thick leaf mat (Stebbins and Lowe 1951). The salamanders tend to be active at cold water temperatures ranging between 5 and 10 degrees Celsius. Larvae are most common in gravel through which water is percolating, and adults prefer the splash zones of waterfalls, under large loose sheets of rock on faces where a thin layer of water is running (Good and Wake 1992). Rhyacotriton olympicus are associated with old growth forest, with Douglas fir, tanbark oak, bay, madrone, alder, and maple as common species (Good and Wake 1992; Stebbins and Lowe 1951). Adults can be found away from stream or spring habitat, mostly after heavy rains (Nussbaum et al. 1983).

This species can be found in the Olympic Peninsula in Clallam, Grays Harbor, Jefferson, and Mason counties, Washington, United States (Good and Wake 1992).

endemic to a single state or province

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (5000-20,000 square km (about 2000-8000 square miles)) Olympic Peninsula in Clallam, Grays Harbor, Jefferson, and Mason counties, Washington (Good and Wake 1992).

Length: 12 cm

Differs from all other RYACOTRITON by the presence in adults and larger larvae of a distinct wavy line of demarcation between the dorsal and ventral ground color and large, well-defined dark spots scattered over the ventral surface; differs from VARIEGATUS and CASCADAE also by the absence of dorsal spotting or blotching (Good and Wake 1992).

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Comments: Coastal coniferous forests in small, cold mountain streams and spring seepages. Larvae often occur under stones in shaded streams. Adults also inhabit these streams or streamsides in saturated moss-covered talus, or under rocks in splash zone. Primarily in older forest sites; required microclimatic and microhabitat conditions generally exist only in older forests (Welsh 1990). Two Rhyacotriton were found in deep, narrow rock crevices; eggs were lying in cold, slow-moving water (Nussbaum et al. 1983).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Comments: Opportunistic. Larvae feed on aquatic invertebrates such as flatworms, annelids, snails, arachnids, crustaceans, and insects. Adults eat aquatic/semi-aquatic invertebrates, including beetles, stoneflies, snails, flies, amphipods, etc. (Nussbaum et al. 1983).

Adults are very sensitive to desiccation.

Mean clutch size (based on yolked ovarian follicles) = 7.9 (Good and Wake 1992). Larval period lasts probably 3-4.5 years (Nussbaum and Tait 1977). Sexually mature 1.0-1.5 years after metamorphosis (Behler and King 1979; Nussbaum et al. 1983).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 5
Species With Barcodes: 1

Year Assessed

Assessor/s

Reviewer/s

Justification

United States

Rounded National Status Rank: N3 - Vulnerable

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Small range in the Olympic Peninsula, Washington; threats include loss/degradation of cold stream habitat by timber harvest.

Intrinsic Vulnerability: Highly to moderately vulnerable.

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Global Short Term Trend: Relatively stable (=10% change)

Comments: Likely relatively stable in recent years.

Global Long Term Trend: Relatively stable to decline of 50%

Comments: Likely relatively stable in extent of occurrence, uncertain degree of decline in population size, area of occurrence, and number/condition of occurrences.

Most breeding of R. olympicus occurs in spring and early summer. The sexually active male may perform a tail-wagging display towards the female prior to spermatophore deposition, curling the tail and arching the back (Arnold 1977). Females laying single, unpigmented eggs in clusters of 2-16 (Stebbins and Lowe 1951; Stebbins 1985), but larger clusters may be found due to communal egg laying (Nussbaum 1969; Stebbins 1985). There is apparently no attendance of the developing eggs (Nussbaum 1969; Nussbaum and Tait 1977). In other species of Rhyacotriton, egg deposition sites are in seeps at the heads of springs and this is likely to be similar in R. olympicus (Nussbaum 1969). Clutch frequency is once per year (Nussbaum et al. 1983). Research on other species of Rhyacotriton indicates that females may lay at any time of the year, but tend to lay in late spring (Nussbaum and Tait 1977). Larvae may take over three years to metamorphose, and metamorphosis usually occurs between 30 and 40cm SVL (Stebbins 1985; Nussbaum et al. 1983).

The larval diet may include a variety of aquatic invertebrates, an varies with availability and location (Nussbaum et al. 1983). The diet of metamorphosed Rhyacotriton includes aquatic and semi-aquatic invertebrates, as well as larval and adult beetles, flies, earthworms, snails and other invertebrates (Nussbaum et al. 1983).

Predators of Rhyacotriton probably include the giant salamander, Dicamptodon, and garter snakes, but have not been reported (Nussbaum et al. 1983). Large larvae and adults may exhibit a defensive behavior consisting of coiling the body and elevating and undulating the tail, exposing the bright yellow underside (Nussbaum et al. 1983).

Population

Population Trend

Degree of Threat: Medium

Comments: Sensitive to increased temperature and sedimentation. Timber harvest negatively affects Rhyacotriton salamanders more than any other sympatric amphibians (Bury and Corn 1988, Corn and Bury 1989). Some populations are isolated by intervening areas of unsuitable habitat; these are vulnerable to extirpation through natural processes exacerbated by timber harvest (especially old growth stands on north-facing slopes).

Although Rhyacotriton is abundant in its habitat, it is associated with old-growth forest, and is virtually absent from recently logged areas, most likely due to decreased temperatures, increased humidity, and susceptibility to desiccation (Good and Wake 1992; Stebbins and Lowe 1952).

Major Threats

Conservation Actions

Needs: See Thomas et al. (1993).