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Rhyacotriton cascadae

Good and Wake, 1992

Cascade Torrent Salamander

G3Vulnerable Found in 22 roadless areas NatureServe Explorer →
G3VulnerableGlobal Rank
Near threatenedIUCN
Very high - highThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.102976
Element CodeAAAAJ01030
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVertebrate Animal
IUCNNear threatened
Endemicendemic to a single nation
KingdomAnimalia
PhylumCraniata
ClassAmphibia
OrderCaudata
FamilyRhyacotritonidae
GenusRhyacotriton
Concept Reference
Good, D. A., and D. B. Wake. 1992. Geographic variation and speciation in the torrent salamanders of the genus Rhyacotriton (Caudata: Rhyacotritonidae). University of California Publications in Zoology 126:i-xii, 1-91.
Taxonomic Comments
The genus Rhyacotriton previously contained a single species R. olympicus. Based on genetic differentiation, Good and Wake (1992) split olympicus into 4 species: R. olympicus, R. variegatus, R. kezeri, and R. cascadae. Highton (2000) interpreted their data as showing that R. cascadae likely encompasses two species.

Good and Wake (1992) removed Rhyacotriton from the family Dicamptodontidae and established it as the sole member of the family Rhyacotritonidae.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2022-08-01
Change Date2001-11-28
Edition Date2022-08-01
Edition AuthorsHammerson, G., K. J. Popper, and L. Hallock (2004), Gaines, E. (2022)
Threat ImpactVery high - high
Range Extent5000-20,000 square km (about 2000-8000 square miles)
Number of Occurrences81 - 300
Rank Reasons
Small range in western Washington and Oregon; major threat is loss/degradation of habitat, such as may result from logging. It requires clear headwater streams and subsurface flows with cold water, high canopy cover, and cobble. Many occurrences are under federal ownership.
Range Extent Comments
This species occurs along the west slope of the Cascade Mountains from just north the Cowlitz River in Lewis County, Washington, to within 0.5 km north of the Middle Fork of the Willamette River, Lane County, Oregon, USA (Good and Wake 1992, Wagner et al. 2006, Howell and Maggiulli 2011).
Occurrences Comments
Because of low dispersal ability, the number of occupied 4km2 grid cells is likely a reasonable estimation of the number of occurrences (Nijhuis and Kaplan 1998, Steele et al. 2003, Howell and Maggiulli 2011, ORBIC 2022). Alternatively, the species is present in 82 6th field watersheds.
Threat Impact Comments
The main threats to this species include activities that result in increased stream temperature, sedimentation, altered flow, and habitat fragmentation, including timber harvest and road construction and maintenance (Howell and Maggiulli 2011). Timber harvest and removal of streamside vegetation can degrade habitat by causing increased water temperatures, increased sedimentation, and altered flows (Steele et al. 2003, Howell and Maggiulli 2011). Densities were significantly lower in streams in managed forests than in streams in unharvested forests, though presence of riparian buffers can help to mitigate this threat (Pollett et al. 2010). Road construction and maintenance, including for logging, can have negative impacts to this species through increased sedimentation, altered flows. Roads and culverts may also pose a barrier to movement, particularly in a species with limited dispersal ability (Howell and Maggiulli 2011). Herbicides to suppress the shrub layer on forest lands after harvest, or to control invasive vegetation, could have the potential to negatively impact Rhyacotriton cascadae (Howell and Maggiulli 2011).
This species is highly vulnerable to climate change due to anticipated changes in stream temperature and flow (Case 2014, Washington Department of Fish and Wildlife 2022). Climate change is expected to result in more frequent and intense fires in the range of this species which may result in increased stream temperature and sedimentation (Howell and Maggiulli 2011). Managed fire is rare in the range of this species. Other suspected threats include disease and parasites, including chytrid fungus and viruses, the impact of this threat is unknown (Howell and Maggiulli 2011). Threats may be exacerbated by the species' limited dispersal capacity (Nijhuis and Kaplan 1998, Steele et al. 2003), limiting gene flow and the ability to recolonize areas after disturbance (Howell and Maggiulli 2011).
Ecology & Habitat

Description

For all species in the genus, mean SVL for the largest 10% of adults is between 5 and 6 cm.

Diagnostic Characteristics

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

These salamanders generally are found in high-gradient, permanent, cool or cold-water sources, such as seeps, waterfalls, headwaters, and edges of larger streams in coniferous forests (Howell and Maggiulli 2011). Larvae often occur under stones in shaded streams. Adults also inhabit these streams or stream sides in saturated moss-covered talus, or under rocks in splash zone. In the Willamette National Forest, average stream depth was 4–5 cm, with limited amounts of riffle in channel units, channel substrate was cobbles and boulder, and occupied sites had high canopy cover and some mid-story cover along the stream (Hunter 1998). Densities were significantly lower in streams in managed forests than in streams in unharvested forests, though in harvested forests, they were significantly more abundant in streams with a buffer between streams and harvest activity (Pollett et al. 2010). Although this species is associated with older forests, Rhyacotriton 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). Only one nest has been described for this species, in an area with low flow, cobble, and minimal sediment (MacCracken 2004).

Ecology

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 longer distance movements (up to 800m) have been reported under cool, wet conditions (Howell and Maggiulli 2011). Rhyacotriton are very sensitive to desiccation (Ray 1958).

Reproduction

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).
Terrestrial Habitats
Forest - ConiferBare rock/talus/scree
Palustrine Habitats
Riparian
Other Nations (1)
United StatesN3
ProvinceRankNative
OregonS2Yes
WashingtonS3Yes
Threat Assessments
ThreatScopeSeverityTiming
4 - Transportation & service corridorsRestricted (11-30%)Serious - slightHigh (continuing)
4.1 - Roads & railroadsRestricted (11-30%)Serious - slightHigh (continuing)
5 - Biological resource useLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
5.3 - Logging & wood harvestingLarge (31-70%)Serious or 31-70% pop. declineHigh (continuing)
7 - Natural system modificationsSmall (1-10%)Slight or 1-10% pop. declineHigh (continuing)
7.1 - Fire & fire suppressionSmall (1-10%)Slight or 1-10% pop. declineHigh (continuing)
7.1.1 - Increase in fire frequency/intensitySmall (1-10%)Slight or 1-10% pop. declineHigh (continuing)
8 - Invasive & other problematic species, genes & diseasesSmall (1-10%)UnknownHigh (continuing)
9 - PollutionSmall (1-10%)Unknown—
9.3 - Agricultural & forestry effluentsSmall (1-10%)Unknown—
9.3.3 - Herbicides and pesticidesSmall (1-10%)Unknown—
11 - Climate change & severe weatherPervasive (71-100%)Serious - moderateHigh (continuing)

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Roadless Areas (22)
Oregon (14)
AreaForestAcres
Bull Of The WoodsMt. Hood National Forest8,843
EagleMt. Hood National Forest16,841
ElkhornWillamette National Forest9,380
Gordon MeadowsWillamette National Forest9,463
Hardesty MountainUmpqua National Forest2,597
LarchMt. Hood National Forest12,961
Menagerie (rooster Rock)Willamette National Forest374
Middle SantiamWillamette National Forest7,316
Moose LakeWillamette National Forest5,013
Mt. HagenWillamette National Forest6,406
Opal CreekWillamette National Forest5,417
Roaring RiverMt. Hood National Forest27,316
Salmon - HuckleberryMt. Hood National Forest17,570
Wind CreekMt. Hood National Forest5,438
Washington (8)
AreaForestAcres
Bear CreekGifford Pinchot National Forest7,980
Big Lava BedGifford Pinchot National Forest19,043
BourbonGifford Pinchot National Forest4,512
Dark DivideGifford Pinchot National Forest52,483
PompeyGifford Pinchot National Forest23,985
Silver StarGifford Pinchot National Forest7,779
SiouxonGifford Pinchot National Forest12,773
TumwaterGifford Pinchot National Forest8,676
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