Rana cascadae Slater, 1939
Christopher A. Pearl 1
Michael J. Adams2
1. Historical versus Current Distribution. Cascade frogs (Rana cascadae) historically occupied moderate and high elevation (about 400–2,500 m) lentic habitats throughout the Cascade Range, from the very northern edge of California’s Sierra Nevada to within 25 km of the British Columbia border (Dunlap and Storm, 1951; Dunlap, 1955; Dumas, 1966; Bury, 1973a; Hayes and Cliff, 1982; Nussbaum et al., 1983; Fellers and Drost, 1993; Jennings and Hayes, 1994a; K.R. McAllister, 1995). Population systems occurring in the Olympic Mountains of Washington and the Trinity Alps, Mt. Shasta, and Mt. Lassen areas of California are notably disjunct from the main Cascade axis and may warrant investigation for cryptic taxa (Jennings and Hayes, 1994a; K. Monson and M. Blouin, unpublished data). Range contractions have been documented in the southern end of their range (Fellers and Drost, 1993; Jennings and Hayes, 1994a). Jennings and Hayes (1994a) and Fellers and Drost (1993) estimate that Cascade frogs are extirpated from about 99% of their southernmost population clusters (Mt. Lassen and surroundings), and 50% of their total historical distribution in California.
2. Historical versus Current Abundance. Cascade frogs are among the most commonly encountered lentic breeders in Olympic and Mount Rainier national parks, where extensive surveys suggest no evidence of declines (Adams et al., 2001; Tyler et al., 2002). Cascade frogs were among the first amphibians to recolonize sites post eruption and are now commonly encountered in Mount St. Helens Volcanic Monument in the southern Washington Cascades (Karlstrom, 1986; Crisafulli and Hawkins, 1998; C. Crisafulli, personal communication). Some concerns for declines in the central Oregon Cascade Range have been reported (Nussbaum et al., 1983; Blaustein and Wake, 1990), but other surveys do not suggest exceptionally low site occupancy rates (C. Brown, 1997; C.A.P., B. Bury, and M.J.A., unpublished data). Recent surveys suggest that Cascade frogs remain present in portions of the Trinity Alps and Marble Mountains, but are rare to nonexistent in other Californian portions of their historical range (G. Fellers, H. Welsh, personal communications). Declines have been documented around Lassen Volcanic National Park in northeastern California, where Cascade frogs were historically widespread and abundant between 1,450 and 2,480 m (Grinnell et al., 1930; Badaracco, 1962). In 1991, Cascade frogs were detected at only 1 of 50 sites in the vicinity of Lassen Volcanic National Park, 16 of which historically supported this species (Fellers and Drost, 1993). More recent surveys (1992–2002) have detected Cascade frogs at only 4 of 400 sites (G. Fellers, personal communication). Population sizes were small at all four sites, and as of 2002, frogs had disappeared from two of these four sites (G. Fellers, personal communication).
3. Life History Features.
i. Breeding migrations. Available information suggests that Cascade frog adults overwinter near breeding localities and, because they often become active during ice thaw, are thought not to make extensive breeding migrations (Briggs, 1976, 1987; O’Hara, 1981).
ii. Breeding habitat. Cascade frogs breed in temporary and permanent lentic waters, often in smaller bodies of water nearer larger lakes (Nussbaum et al., 1983; Briggs, 1987; Bury and Major, 1997). In Olympic National Park, Washington, Cascade frog breeding sites generally have silt/mud substrates, lack fish, and have low UV-B transmission (Adams et al., 2001).
i. Egg deposition sites. First egg masses are deposited in comparatively warm water along gradually sloping shorelines, often over soft substrates protected from severe wave action (Sype, 1975; O’Hara, 1981). Breeding is explosive (often completed in < 1 wk), and egg masses are commonly deposited in aggregations (Sype, 1975; Briggs, 1987). The placement of clusters of egg masses in shallow water soon after first thaw can make them susceptible to freezing mortality, pathogen transmission between adjacent masses, or desiccation associated with receding water levels (Blaustein and Olson, 1991; Kiesecker and Blaustein, 1997b; C.A.P., personal observations).
ii. Clutch size. Egg masses contain between 300–800 ova (O’Hara, 1981; Nussbaum et al., 1983). Adults appear to be strongly philopatric, using the same breeding sites for several years (O’Hara, 1981; Olson, 1992). Females breed no more than once/year, but whether they skip years remains unknown (Sype, 1975; Nussbaum et al., 1983).
i. Length of larval stage. Water temperatures strongly influence rates of development, hatching, and time to metamorphosis (Sype, 1975). Metamorphosis is generally achieved about 2 mo after hatching (Nussbaum et al., 1983; Briggs, 1987). There is no documentation of overwintering larvae, but the topic warrants further investigation.
ii. Larval requirements.
a. Food. Larvae are thought to be primarily benthic feeders, but specific preferences are not well known (Nussbaum et al., 1983).
b. Cover. Larvae often form loose aggregations near their oviposition sites. Aggregations usually include kin (O’Hara and Blaustein, 1985) and are generally associated with flooded vegetation in warm microhabitats (O’Hara, 1981; Wollmuth et al., 1987).
iii. Larval polymorphisms. Not reported. Albino larvae have been observed three times in the central Cascade Range of Oregon (Altig and Brodie, 1968; B. McCreary, personal communication).
vi. Features of metamorphosis. In laboratory trials, size at metamorphosis varies from 15–30 mm SVL and depends on larval density, food availability, and water temperature (Blaustein et al., 1984). Larvae reared in 23 ˚C lab water averaged 20–21 mm SVL at metamorphosis after 37.5 d (Nussbaum et al., 1983). Larval growth rate can affect shape (e.g., leg length) at metamorphosis (Blouin and Brown, 2000).
v. Post-metamorphic migrations. Specific information is lacking.
D. Juvenile Habitat. Similar to adults, especially marshy fringes of lentic environments, but detailed information is not yet available (C.A.P., personal observation).
E. Adult Habitat. Cascade frog adults utilize an array of habitat types, but are generally associated with open wetland habitats at higher elevations (C. Brown, 1997; Bury and Major, 1997; Bosakowski, 1999; Olson, 2001). Cascade frog adults commonly occupy moist meadows and can be found in relatively small permanent and temporary ponds (Sype, 1975; O’Hara, 1981; Olson, 1992). Adults are also found along streams in summer, especially at lower elevations where lentic habitats are less common (Dunlap, 1955; C.A.P., personal observations). Adults generally stay close to water, particularly along sunny shores, under dry summer conditions, but can be found traversing uplands during high humidity (Nussbaum et al., 1983). Adults and breeding can occur in anthropogenic wetland habitats such as pump chances (Quinn et al., 2001).
F. Home Range Size. Unknown.
G. Territories. While adults are not considered territorial (Nussbaum et al., 1983), males will behave aggressively toward one another during breeding (C.A.P., personal observation).
H. Aestivation/Avoiding Dessication. Not reported; summer is their active season.
I. Seasonal Migrations. See "Breeding migrations" and "Juvenile Habitat" above.
J. Torpor (Hibernation). Cascade frogs hibernate through the long, snowy winters typical of most of their range (Nussbaum et al., 1983). Frogs have been recovered from mud beneath 0.3–1.0 m of water and from spring-saturated areas around ponds (Briggs, 1987).
K. Interspecific Associations/Exclusions. Cascade frogs may share breeding sites with western toads (Bufo boreas), northwestern salamanders (Ambystoma gracile), long-toed salamanders (A. macrodactylum), rough-skinned newts (Taricha granulosa), and Pacific treefrogs (Pseudacris regilla). They also occur syntopically with Oregon spotted frogs (Rana pretiosa) at < 10 sites along the Oregon Cascades and can co-occur with northern red-legged frogs (Rana aurora) at sites in lower elevations (C.A.P., personal observations). Several researchers have suggested that Cascade frogs may be reduced in number by introduced sport-fish (Fellers and Drost, 1993; Jennings and Hayes, 1994a).
L. Age/Size at Reproductive Maturity. In the Oregon Cascades, males and females are thought to reach sexual maturity at 2–3 yr (about 35–40 mm) and 4 yr (about 50–55 mm) post metamorphosis, respectively (Briggs and Storm, 1970; Olson, 1992; Jennings and Hayes, 1994a).
M. Longevity. In the Oregon Cascades, both males and females are thought to live > 5 yr, sometimes reaching 7 yr (Briggs and Storm, 1970; Olson, 1992).
N. Feeding Behavior. Diet composition of Cascade frogs is poorly known, but adults are thought to consume a variety of invertebrate prey and will occasionally consume conspecifics (Rombough et al., 2003).
O. Predators. Native predators of adult frogs include water bugs (Belostomatidae), garter snakes (especially common garter snakes, Thamnophis sirtalis), mustelid mammals, raccoons, and several bird species (Briggs and Storm, 1970; Nussbaum et al., 1983; Nauman and Dettlaff, 1999). Larvae and newly metamorphosed individuals are taken by invertebrates (Belostomatidae, Dytiscidae, Odonata), and aquatic salamanders (rough-skinned newts, northwestern salamanders, and long-toed salamanders; Briggs and Storm, 1970; Peterson and Blaustein, 1991, 1992). Juvenile and adult Cascade frogs are known to cannibalize larvae and newly metamorphosed animals (Rombough et al., 2003). Introduced salmonids are now widespread in high lakes throughout the range of Cascade frogs and may represent a common predator of larvae and small adults (Hayes and Jennings, 1986; Fellers and Drost, 1993; Jennings and Hayes, 1994a; Simons, 1998).
P. Anti-Predator Mechanisms. In laboratory trials, larvae increased activity when exposed to waterborne chemical cues of injured conspecifics (Hews and Blaustein, 1985). Chemical cues of predatory leeches can elicit early hatching of eggs (Chivers et al., 2001). Adult escape behavior often includes a series of rapid bounds into water, followed by burrowing head-first into unconsolidated substrate (C.A.P., personal observations).
Q. Diseases. Field experiments suggest that the oomycete fungus, Saprolegnia ferax, is related to embryonic mortality in Cascade frogs and may be enhanced by other stressors such as ultraviolet radiation (Kiesecker and Blaustein, 1995, 1997b).
R. Parasites. The blood parasite Lankesterella sp. was reported in Cascade frogs by Clark et al. (1969). Cascade frogs exhibited lower malformation frequencies attributable to metacercariae of the trematode Ribeiroia ondatrae relative to other Pacific Northwestern amphibians (Johnson et al., 2002).
4. Conservation. A latitudinal gradient of conservation status apparently exists for Cascade frogs, with declines documented in the southern portion of their range but not in study areas to the north (see "Historical versus Current Distribution" and "Historical versus Current Abundance" above). Recent surveys in northern California suggest that populations in the region are often small, and that their abundance and distribution is negatively associated with introduced salmonids (Fellers and Drost, 1993; H. Welsh, G. Fellers, personal communications). Declines have been referenced in Oregon (Blaustein and Wake, 1990), but field data from the northern and central Oregon Cascades suggest the species remains widespread in some areas and has the capacity to rebound from short-term declines (Olson, 1992; C. Brown, 1997; C.A.P. and colleagues, personal observations). Cascade frogs remain widespread and common in Olympic and Mount Rainier national parks, and in the Mt. St. Helens Volcanic Monument in Washington (Karlstrom, 1986; Crisafulli and Hawkins, 1998; Adams et al., 2001; Tyler et al., 2002). Cascade frogs are considered a Species of Special Concern in California (California Department of Fish and Game, 1999), and Sensitive-Vulnerable in Oregon (Oregon Natural Heritage Program, 1995).
Causes of Cascade frog declines are not fully known, but introduced trout, UV-B radiation, fungal pathogens, and loss of open meadow habitat due to fire suppression have been suggested (Hayes and Jennings, 1986; Fellers and Drost, 1993; Blaustein et al., 1994b,c; Kiesecker and Blaustein, 1995; Fite et al., 1998; Adams et al., 2001). In Oregon, Casacde frog embryos have low photolyase levels and therefore low capacity to repair UV-B damage; they demonstrate reduced hatching in unshielded relative to shielded in situ enclosures (Blaustein et al., 1994c). However, breeding sites in the Oregon and Washington portions of the species' range may be afforded some protection from lethal UV-B doses by dissolved organic matter (Palen et al., 2002). One Oregon study failed to detect short-term changes in breeding phenology that might be attributable to climate change (Blaustein et al., 2001). Fertilizers such as urea may pose a threat to Cascade frogs, as juveniles do not appear capable of sensing and avoiding toxic levels in laboratory studies (Hatch et al., 2001). Nitrites may affect behavior and metamorphosis of Cascade frog larvae (Marco and Blaustein, 1999). An improved understanding of microhabitat associations and interactions with introduced fish is needed to assist with conservation measures for the species (Olson, 2001).
1Christopher A. Pearl
USGS Forest and Rangeland Ecosystem Science Center
3200 SW Jefferson Way
Corvallis, Oregon 97331
2Michael J. Adams
USGS Forest and Rangeland Ecosystem Science Center
3200 SW Jefferson Way
Corvallis, Oregon 97331
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 14 Jul 2020.
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