Rhyacotriton cascadae

A small to medium-sized, semi-aquatic salamander. Dorsal coloration is brown and the underside is bright yellow. Black flecks or spots occur on the back and more densely on the sides. The degree of black spotting or blotching varies with locality, but there seems to be no geographic pattern. The belly sometimes has small grayish flecks. Some populations have a dark stripe on the underside of the tail, posterior to the vent opening. Males have squared, glandular lobes on either side of the vent opening, a trait unique among salamanders (Sever 1988). These salamanders have a short, rounded snout and relatively large, prominent eyes. The tail is relatively short, less than the snout to vent length. Description from Good and Wake (1992),Leonard et al. (1993), and Petranka (1998). Adult body size is 4.0 to 5.1 cm snout to vent length (7.5 - 11 cm total length) (Good and Wake 1992; Petranka 1998). Females are slightly larger than males (Good and Wake 1992).Larvae are of the stream type, with very short gills and a low dorsal tail fin that does not extend onto the back. Coloration is similar to the adult pattern (Stebbins 1985; Leonard et al. 1993).Hatchling size is about 15.8 mm snout to vent length (Nussbaum and Tait 1977).

Until recently the genus Rhyacotriton contained a single species with two subspecies, R. o. olympicus and R. o. variegatus. Genetic studies revealed substantial variation and subdivision throughout the range and the single species was split into four species: R. olympicus, R. variegatus, R. cascadae, and R. kezeri (Good et al. 1987; Good and Wake 1992).

The distribution of R. cascadae is restricted to the western slope of the Cascades Mountains from just north of Mt. St. Helens, Skamania Co., Washington, to northeastern Lane Co., Oregon (Good and Wake 1992). Torrent salamanders inhabit forested areas with high humidity and dense canopy cover (Good and Wake 1992; Nussbaum et al. 1993).Individuals are found near seepages and small, rocky streams, preferring to occupy the splash zone (Nussbaum and Tait 1977; Petranka 1998). Larvae are usually found in loose gravel.Adults are rarely found more than a meter from the streams edge (Good and Wake 1992).

This species can be found on the west slope of the Cascade Mountains from just north of Mount Saint Helens, Skamania County, Washington, south to north-eastern Lane County, Oregon, USA (Good and Wake 1992).

endemic to a single nation

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)) West slope of the Cascade Mountains from just north of Mount Saint Helens, Skamania County, Washington, south to northeastern Lane County, Oregon (Good and Wake 1992).

Length: 12 cm

R. CASCADAE: highly variable; no unique diagnostic characteristics of color pattern; most differ from OLYMPICUS and KEZERI by heavy spotting and blotching of the dorsal surfaces, especially along the sides (these spots also are usually denser than those in VARIEGATUS, although there is considerable variation in both species); heavy spotting on the sides usually makes the line of demarcation between the dorsal and ventral ground color more distinct than in either KEZERI or VARIEGATUS, regardless of the degree of spotting in the latter species; this line of demarcation is wavy in OLYMPICUS, relatively straight in CASCADAE; a dark preorbital stripe found in heavily spotted VARIEGATUS usually is weak or absent in CASCADAE; ventral pattern is variable but many populations have ventral spotting in the form of fine grayish flecking that is especially abundant on the throat and chest; others have a dark band across the ventral surface just posterior to the cloaca (Good and Wake 1992).

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Comments: These salamanders generally are found in 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. Rhyacotriton species occur primarily in older forest sites; required microclimatic and microhabitat conditions generally exist only in older forests (Welsh 1990). However, R. cascadae survived in many sites that were completely deforested by the 1980 eruption of Mount St. Helens, indicating that "forest cover may not be a critical habitat feature at higher elevations" (Jones et al. 2005). Two Rhyacotriton nests were found in deep, narrow rock crevices; eggs were lying in cold, slow-moving water (Nussbaum et al. 1983). MacCraken (2004, Herpetol. Rev. 35:367) reported what he believed to be a nest of 5 eggs under a cobble in a 2nd-order stream, but the species identification was circumstantial.

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).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: McAllister (1995) mapped approximately 53 collection or verified sighting locations in Washington. E. Gaines (pers. comm., 1997) estimated that the number of occurrences in Oregon falls between 21 and 100.

Unknown

Comments: Fairly common in appropriate habitat.

Nijhuis and Kaplan (1998) found that density in spring was 0.31-8.33 individuals (including immatures) per sq m; mean home range length over three months was 2.4 m (but long distance movements may not have been detected).

Adults are very sensitive to desiccation.

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

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 western Washington and Oregon; major threat is loss/degradation of habitat, such as may result from logging.

Intrinsic Vulnerability: Highly to moderately vulnerable.

Environmental Specificity: Very narrow to narrow.

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

Comments: Stable in Oregon (E. Gaines, pers. comm., 1997).

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

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

Courtship has not been observed for any species of Rhyacotriton (Petranka 1998). Courtship and mating occur over most of the year, concentrated in the fall and spring months, based on the presence of spermatophores in the cloacae of females. Females may oviposit at any time of the year, but tend to lay in late spring (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. cascadae (Nussbaum 1969). Number of mature ovarian eggs (correlated with clutch size) ranges from 2-13 (Nussbaum and Tait 1977), and average clutch size is 8 (Nussbaum and Tait 1977; Good and Wake 1992). In a nest of the closely related species R. kezeri, at least three females may have laid their eggs communally (Nussbaum 1969).There is apparently no attendance of the developing eggs (Nussbaum 1969; Nussbaum and Tait 1977). Clutch frequency is once per year (Nussbaum and Tait 1977; Nussbaum et al. 1983). Eggs laid in spring hatch 5-6 months later (Nussbaum 1969).

Information on diet of R. cascadae is not available, but adults and juveniles likely feed on a mixture of aquatic and semiaquatic invertebrates. Likewise, natural predators have not been documented but larval and adult Pacific giant salamanders (Dicamptodon), as well as garter snakes (Thamnophis) are probably important. See Petranka (1998) and references therein. Rhyacotriton respond to attacks by coiling the body and raising and undulating the tail which contains poison glands (Nussbaum et al. 1983).

Larvae may be abundant and densities have been estimated at 28 - 41 individuals/m² (Nussbaum and Tait 1977).

Population

Population Trend

Degree of Threat: Medium

Comments: Sensitive to increased temperature and sedimentation, such as may result from logging or logging road construction. Timber harvest negatively affects Rhyacotriton salamanders more than it does other 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). Moderately threatened in Oregon (E. Gaines, pers. comm., 1997).

Logging of old-growth forests is the main threat to populations of R. cascadae. Larvae are likely affected by increased siltation following logging, and adults are sensitive to environmental temperature and moisture levels. Logging also eliminates suitable habitat (Bury 1983; Good and Wake 1992; Petranka 1998; Welsh and Lind 1991).

Major Threats

Conservation Actions

Global Protection: Unknown whether any occurrences are appropriately protected and managed

Comments: No known adequately protected occurrences in Oregon.

Needs: See Thomas et al. (1993).