Overview

Comprehensive Description

Description

This frog is a member of the mountain yellow-legged frog complex, which is comprised of two species: Rana muscosa and Rana sierrae. Both species are highly aquatic and are always found within a meter or two from the edge of water. Like Rana sierrae, Rana muscosa is yellowish or reddish brown from above, with black or brown spots or lichen-like markings. Toe tips are usually dusky. Underside of hind legs and sometimes entire belly is yellow or slightly orange, usually more opaque than in the Foothill Yellow-legged Frog, Rana boylii. Yellow coloration often extends forward to level of forelimbs. Dorsolateral folds present but frequently indistinct. The tadpoles are black or dark brown and are large (total length often exceeds 10 cm) and metamorphose in 1-4 years depending on the elevation.

Rana muscosa differs from Rana sierrae in having relatively longer legs. When a leg is folded against the body the tibio-tarsal joint typically extends beyond the external nares. The mating call of R. muscosa is significantly different from that of R. sierrae in that they lack transitions between pulsed and noted sounds. Both species call underwater. Males can be heard above water but only from a short distance away (<2 meters). The two species also differ in mitochondrial DNA. The mitochondrial DNA, male advertisement calls, and morphology datasets are geographically concordant (Vredenburg et al. 2007).

The southern California populations of the species were formally recognized as an Endangered distinct population segment as of July 2, 2002. For details please see the U.S. Federal Register at:

  • Southern California populations Endangered

    • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
    • Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.
    • Stebbins, R. C. (2003). Western Reptiles and Amphibians, Third Edition. Houghton Mifflin, Boston.
    • Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. (1998). "Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America." Proceedings of the National Academy of Sciences of the United States of America, 95(15), 9031-9036.
    • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
    • Jennings, M. R., and Hayes, M. P. (1994). ''Amphibian and reptile species of special concern in California.'' Final Report #8023 Submitted to the California Department of Fish and Game. California Department of Fish and Game, Sacramento, California..
    • Drost, C. A., and Fellers, G. M. (1996). "Collapse of a regional frog fauna in the Yosemite area of the California Sierra Nevada, USA." Conservation Biology, 10(2), 414-425.
    • Bradford, D. F. (1989). "Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California: implication of the negative effect of fish introductions." Copeia, 1989, 775-778.
    • Bradford, D. F. (1989). ''Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California USA: Implication of the negative effect of fish introductions.'' Copeia, 1989(3), 775-778.
    • Bradford, D. F., Tabatabai, F., and Graber, D. M. (1993). ''Isolation of remaining populations of the native frog, Rana muscosa, by introduced fishes in Sequoia and Kings Canyon National Parks, California.'' Conservation Biology, 7, 882-888.
    • Briggs, C. J., Knapp, R. A., and Vredenburg, V. T. (2010). ''Enzootic and epizootic dynamics of the chytrid fungal pathogen of amphibians.'' Proceedings of the National Academy of Sciences, 107(21), 9695-9700 .
    • Davidson, C. (2004). ''Declining downwind: Amphibian population declines in California and historical pesticide use.'' Ecological Applications, 14, 1892-1902.
    • Davidson, C., Shaffer, H. B., and Jennings, M. R. (2002). ''Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines.'' Conservation Biology, 16, 1588-1601.
    • Finlay, J. and Vredenburg, V. T. (2007). ''Introduced trout sever trophic connections between lakes and watersheds: consequences for a declining montane frog.'' Ecology, 88(9), 2187-2198.
    • Grinnell, J., and Storer, T. I. (1924). Animal Life in the Yosemite. University of California Press, Berkeley, California.
    • Knapp, R. A. and Matthews, F. (2000). ''Non-native fish introductions and the decline of the Mountain Yellow-legged Frog from within protected areas.'' Conservation Biology, 14(2), 428-439.
    • Knapp, R. A., Boiano, D. M., Vredenburg, V. T. (2007). ''Recovery of a declining amphibian (Mountain Yellow-legged Frog, Rana muscosa) following removal of non-native fish.'' Biological Conservation, 135, 11-20.
    • Knapp, R.A. (1996). ''Non-native trout in the natural lakes of the Sierra Nevada: an analysis of their distribution and impacts on native aquatic biota.'' Sierra Nevada Ecosystem Project, Final Report to Congress, Center for Water and Wildland Resources, University of California (Davis), Davis, California, 363-390.
    • Lewis, T. R. (2009). ''New population of mountain yellow-legged frog (Rana muscosa) discovered.'' Herpetological Bulletin, 108, 1-2.
    • Livezey, R. L., and Wright, A. H. (1945). ''Descriptions of four salientian eggs.'' American Midland Naturalist, 34, 701-706.
    • Rachowicz, L. J., Knapp, R. A., Morgan, J. A. T., Stice, M. J., Vredenburg, V. T., Parker, J. M., and Briggs, C. J. (2006). ''Emerging infectious disease as a proximate cause of amphibian mass mortality.'' Ecology, 87, 1671-1683.
    • Salzberg, A. (2009). ''Population of nearly extinct Mountain Yellow-legged Frog discovered.'' Herpetological Digest, 9, 4.
    • Vredenburg, V. T. (2004). ''Reversing introduced species effects: Experimental removal of introduced fish leads to rapid recovery of a declining frog.'' Proceedings of the National Academy of Sciences of the United States of America, 101, 7646-7650.
    • Vredenburg, V. T., (2007). ''Concordant molecular and phenotypic data delineate new taxonomy and conservation priorities for the endangered mountain yellow-legged frog (Ranidae: Rana muscosa).'' Journal of Zoology, 271, 361-374.
    • Vredenburg, V. T., Fellers, G., and Davidson, C. (2005). ''The mountain yellow-legged frog Rana muscosa (Camp 1917).'' Status and conservation of U.S. Amphibians. M. Lannoo, eds., University of California Press, Berkeley, 563-566.
    • Vredenburg, V. T., Knapp, R. A., Tunstall, T. S., and Briggs, C. J. (2010). ''Dynamics of an emerging disease drive large-scale amphibian population extinctions.'' Proceedings of the National Academy of Sciences, 107(21), 9689-9694.
    • Zweifel, R. G. (1955). ''Ecology, distribution, and systematics of frogs of the Rana boylei group.'' University of California Publications in Zoology, 54, 207-292.
    • Voyles, J., Vredenburg, V. T., Tunstall, T. S., Parker, J. M., Briggs, C. J., and Rosenblum, E. B. (2012). ''Pathophysiology in mountain yellow-legged frogs (Rana muscosa) during a chytridiomycosis outbreak .'' PLoS ONE, 7(4), e35374. doi:10.1371/journal.pone.0035374.
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    Distribution

    Range Description

    Rana muscosa occurs in the southern Sierra Nevada of California and in mountains to the south in southern California. In southern California south of the Sierra Nevada, the historical range extended from Palomar Mountain in San Diego County northward and westward through the San Jacinto, San Bernardino, and San Gabriel Mountains of Riverside, San Bernardino, and Los Angeles counties; these formed four isolated clusters of montane populations (Vredenburg et al. 2007). Additionally, the species occurred as an isolated cluster of populations on Breckenridge Mountain, south of the Kern River in Kern County, and in the Sierra Nevada (west of the crest) in Tulare, Inyo and Fresno counties, extending north to Mather Pass (Vredenburg et al. 2007). The mountain ridges that separate the headwaters of the South Fork Kings River from the Middle Fork Kings River, from Mather Pass to the Monarch Divide, form the northern border of the range. Rana muscosa is now extirpated on Palomar and Breckenridge mountains and in much of the former range elsewhere in southern California and the southern Sierra Nevada (USFWS 2006, Vredenburg et al. 2007). Elevational range in southern California is 1,220-7,560 feet (370-2,290 meters (Stebbins 1985, USFWS 2002).
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    Distribution and Habitat

    Rana muscosa is endemic to California, U.S.A. The Southern Mountain Yellow-legged Frog once ranged from Palomar Mountain in San Diego County through the San Jacinto, San Bernardino and San Gabriel Mountains of Riverside, San Bernardino and Los Angeles counties in southern California. These formed four isolated clusters of montane populations. In addition the species occurred as an isolated cluster of populations on Breckenridge Mountain, south of the Kern River in Kern County, and in the Sierra Nevada mountains in Tulare, Inyo, and Fresno counties, extending north to Mather Pass. The distribution of Rana muscosa in the Sierra Nevada is bordered by the crest of Sierra Nevada. No populations occur east of the crest. The mountain ridges that separate the headwaters of the South Fork Kings River from the Middle Fork Kings River, from Mather Pass on the John Muir Trail to the Monarch Divide, form the northern border of the range. R. muscosa is extinct on Palomar and Breckenridge mountains.

    In summer 2009 a population of Rana muscosa was discovered in the San Jacinto Mountains by a team of USGS and San Diego Natural History Museum biologists (Salzberg 2009; Lewis 2009). The frogs were found at two localities in Tahquitz Creek and one of its tributaries, Willow Creek, about 2.5 miles apart (Salzberg 2009; Lewis 2009). The newly discovered San Jacinto population appears to be occupying a larger area than the other known populations, although the extent and population number are not yet known (Salzberg 2009; Lewis 2009). A total of eight other populations are known from the San Jacinto, San Bernardino, and San Gabriel mountain ranges, each occupying less than half a mile of stream (Salzberg 2009; Lewis 2009).

    • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
    • Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.
    • Stebbins, R. C. (2003). Western Reptiles and Amphibians, Third Edition. Houghton Mifflin, Boston.
    • Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. (1998). "Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America." Proceedings of the National Academy of Sciences of the United States of America, 95(15), 9031-9036.
    • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
    • Jennings, M. R., and Hayes, M. P. (1994). ''Amphibian and reptile species of special concern in California.'' Final Report #8023 Submitted to the California Department of Fish and Game. California Department of Fish and Game, Sacramento, California..
    • Drost, C. A., and Fellers, G. M. (1996). "Collapse of a regional frog fauna in the Yosemite area of the California Sierra Nevada, USA." Conservation Biology, 10(2), 414-425.
    • Bradford, D. F. (1989). "Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California: implication of the negative effect of fish introductions." Copeia, 1989, 775-778.
    • Bradford, D. F. (1989). ''Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California USA: Implication of the negative effect of fish introductions.'' Copeia, 1989(3), 775-778.
    • Bradford, D. F., Tabatabai, F., and Graber, D. M. (1993). ''Isolation of remaining populations of the native frog, Rana muscosa, by introduced fishes in Sequoia and Kings Canyon National Parks, California.'' Conservation Biology, 7, 882-888.
    • Briggs, C. J., Knapp, R. A., and Vredenburg, V. T. (2010). ''Enzootic and epizootic dynamics of the chytrid fungal pathogen of amphibians.'' Proceedings of the National Academy of Sciences, 107(21), 9695-9700 .
    • Davidson, C. (2004). ''Declining downwind: Amphibian population declines in California and historical pesticide use.'' Ecological Applications, 14, 1892-1902.
    • Davidson, C., Shaffer, H. B., and Jennings, M. R. (2002). ''Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines.'' Conservation Biology, 16, 1588-1601.
    • Finlay, J. and Vredenburg, V. T. (2007). ''Introduced trout sever trophic connections between lakes and watersheds: consequences for a declining montane frog.'' Ecology, 88(9), 2187-2198.
    • Grinnell, J., and Storer, T. I. (1924). Animal Life in the Yosemite. University of California Press, Berkeley, California.
    • Knapp, R. A. and Matthews, F. (2000). ''Non-native fish introductions and the decline of the Mountain Yellow-legged Frog from within protected areas.'' Conservation Biology, 14(2), 428-439.
    • Knapp, R. A., Boiano, D. M., Vredenburg, V. T. (2007). ''Recovery of a declining amphibian (Mountain Yellow-legged Frog, Rana muscosa) following removal of non-native fish.'' Biological Conservation, 135, 11-20.
    • Knapp, R.A. (1996). ''Non-native trout in the natural lakes of the Sierra Nevada: an analysis of their distribution and impacts on native aquatic biota.'' Sierra Nevada Ecosystem Project, Final Report to Congress, Center for Water and Wildland Resources, University of California (Davis), Davis, California, 363-390.
    • Lewis, T. R. (2009). ''New population of mountain yellow-legged frog (Rana muscosa) discovered.'' Herpetological Bulletin, 108, 1-2.
    • Livezey, R. L., and Wright, A. H. (1945). ''Descriptions of four salientian eggs.'' American Midland Naturalist, 34, 701-706.
    • Rachowicz, L. J., Knapp, R. A., Morgan, J. A. T., Stice, M. J., Vredenburg, V. T., Parker, J. M., and Briggs, C. J. (2006). ''Emerging infectious disease as a proximate cause of amphibian mass mortality.'' Ecology, 87, 1671-1683.
    • Salzberg, A. (2009). ''Population of nearly extinct Mountain Yellow-legged Frog discovered.'' Herpetological Digest, 9, 4.
    • Vredenburg, V. T. (2004). ''Reversing introduced species effects: Experimental removal of introduced fish leads to rapid recovery of a declining frog.'' Proceedings of the National Academy of Sciences of the United States of America, 101, 7646-7650.
    • Vredenburg, V. T., (2007). ''Concordant molecular and phenotypic data delineate new taxonomy and conservation priorities for the endangered mountain yellow-legged frog (Ranidae: Rana muscosa).'' Journal of Zoology, 271, 361-374.
    • Vredenburg, V. T., Fellers, G., and Davidson, C. (2005). ''The mountain yellow-legged frog Rana muscosa (Camp 1917).'' Status and conservation of U.S. Amphibians. M. Lannoo, eds., University of California Press, Berkeley, 563-566.
    • Vredenburg, V. T., Knapp, R. A., Tunstall, T. S., and Briggs, C. J. (2010). ''Dynamics of an emerging disease drive large-scale amphibian population extinctions.'' Proceedings of the National Academy of Sciences, 107(21), 9689-9694.
    • Zweifel, R. G. (1955). ''Ecology, distribution, and systematics of frogs of the Rana boylei group.'' University of California Publications in Zoology, 54, 207-292.
    • Voyles, J., Vredenburg, V. T., Tunstall, T. S., Parker, J. M., Briggs, C. J., and Rosenblum, E. B. (2012). ''Pathophysiology in mountain yellow-legged frogs (Rana muscosa) during a chytridiomycosis outbreak .'' PLoS ONE, 7(4), e35374. doi:10.1371/journal.pone.0035374.
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    endemic to a single nation

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    National Distribution

    United States

    Origin: Native

    Regularity: Regularly occurring

    Currently: Present

    Confidence: Confident

    Type of Residency: Year-round

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    Global Range: (250-20,000 square km (about 100-8000 square miles)) Rana muscosa occurs in the southern Sierra Nevada of California and in mountains to the south in southern California. In southern California south of the Sierra Nevada, the historical range extended from Palomar Mountain in San Diego County northward and westward through the San Jacinto, San Bernardino, and San Gabriel Mountains of Riverside, San Bernardino, and Los Angeles counties; these formed four isolated clusters of montane populations (Vredenburg et al. 2007). Additionally, the species occurred as an isolated cluster of populations on Breckenridge Mountain, south of the Kern River in Kern County, and in the Sierra Nevada (west of the crest) in Tulare, Inyo and Fresno counties, extending north to Mather Pass (Vredenburg et al. 2007). The mountain ridges that separate the headwaters of the South Fork Kings River from the Middle Fork Kings River, from Mather Pass to the Monarch Divide, form the northern border of the range. Rana muscosa is now extirpated on Palomar and Breckenridge mountains and in much of the former range elsewhere in southern California and the southern Sierra Nevada (USFWS 2006, Vredenburg et al. 2007). Elevational range in southern California is 1,220-7,560 feet (370-2,290 meters (Stebbins 1985, USFWS 2002).

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    Physical Description

    Size

    Length: 8 cm

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    Ecology

    Habitat

    Habitat and Ecology

    Habitat and Ecology
    The habitat includes sunny riverbanks, meadow streams, isolated pools, and lake borders in the Sierra Nevada, rocky stream courses in southern California. The species seems to prefer sloping banks with rocks or vegetation to the water's edge (Stebbins 1985). Zweifel (1955) observed that the frogs in southern California are typically found in steep gradient streams in the chaparral belt and may range into small meadow streams at higher elevations. In contrast, Sierran frogs are most abundant in high elevation lakes and slow-moving portions of streams. This frog seldom is found away from water, but it may cross upland areas in moving between summer and winter habitats (Matthews and Pope 1999). Wintering sites include areas nearshore under ledges and in deep underwater crevices (Matthews and Pope 1999).

    In southern California, USFWS (2006) concluded that Rana muscosa requires the following habitat elements: (1) Water source(s) found between 1,214 to 7,546 feet (370 to 2,300 meter) in elevation that are permanent. Water sources include, but are not limited to, streams, rivers, perennial creeks (or permanent plunge pools within intermittent creeks), pools (i.e., a body of impounded water that is contained above a natural dam) and other forms of aquatic habitat. The water source should maintain a natural flow pattern including periodic natural flooding. Aquatic habitats that are used by mountain yellow-legged frog for breeding purposes must maintain water during the entire tadpole growth phase, which can last for up to 2 years. During periods of drought, or less than average rainfall, these breeding sites may not hold water long enough for individuals to complete metamorphosis, but they would still be considered essential breeding habitat in wetter years. Further, the aquatic includes: a. Bank and pool substrates consisting of varying percentages of soil or silt, sand, gravel cobble, rock, and boulders; b. Open gravel banks and rocks projecting above or just beneath the surface of the water for sunning posts; c. Aquatic refugia, including pools with bank overhangs, downfall logs or branches, and/or rocks to provide cover from predators; and d. Streams or stream reaches between known occupied sites that can function as corridors for movement between aquatic habitats used as breeding and/or foraging sites. (2) Riparian habitat and upland vegetation (e.g., ponderosa pine, montane hardwoodconifer, montane riparian woodlands, and chaparral) extending 262 feet (80 meters) from each side of the centerline of each identified stream and its tributaries, that provides areas for feeding and movement of mountain yellow-legged frog, with a canopy overstory not exceeding 85 percent that allows sunlight to reach the stream and thereby provide basking areas for the species.

    Systems
    • Terrestrial
    • Freshwater
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    Comments: The habitat includes sunny riverbanks, meadow streams, isolated pools, and lake borders in the Sierra Nevada, rocky stream courses in southern California. The species seems to prefer sloping banks with rocks or vegetation to the water's edge (Stebbins 1985). Zweifel (1955) observed that the frogs in southern California are typically found in steep gradient streams in the chaparral belt and may range into small meadow streams at higher elevations. In contrast, Sierran frogs are most abundant in high elevation lakes and slow-moving portions of streams. This frog seldom is found away from water, but it may cross upland areas in moving between summer and winter habitats (Matthews and Pope 1999). Wintering sites include areas nearshore under ledges and in deep underwater crevices (Matthews and Pope 1999).

    In southern California, USFWS (2006) concluded that Rana muscosa requires the following habitat elements: (1) Water source(s) found between 1,214 to 7,546 feet (370 to 2,300 meter) in elevation that are permanent. Water sources include, but are not limited to, streams, rivers, perennial creeks (or permanent plunge pools within intermittent creeks), pools (i.e., a body of impounded water that is contained above a natural dam) and other forms of aquatic habitat. The water source should maintain a natural flow pattern including periodic natural flooding. Aquatic habitats that are used by mountain yellow-legged frog for breeding purposes must maintain water during the entire tadpole growth phase, which can last for up to 2 years. During periods of drought, or less than average rainfall, these breeding sites may not hold water long enough for individuals to complete metamorphosis, but they would still be considered essential breeding habitat in wetter years. Further, the aquatic includes: a. Bank and pool substrates consisting of varying percentages of soil or silt, sand, gravel cobble, rock, and boulders; b. Open gravel banks and rocks projecting above or just beneath the surface of the water for sunning posts; c. Aquatic refugia, including pools with bank overhangs, downfall logs or branches, and/or rocks to provide cover from predators; and d. Streams or stream reaches between known occupied sites that can function as corridors for movement between aquatic habitats used as breeding and/or foraging sites. (2) Riparian habitat and upland vegetation (e.g., ponderosa pine, montane hardwoodconifer, montane riparian woodlands, and chaparral) extending 262 feet (80 meters) from each side of the centerline of each identified stream and its tributaries, that provides areas for feeding and movement of mountain yellow-legged frog, with a canopy overstory not exceeding 85 percent that allows sunlight to reach the stream and thereby provide basking areas for the species.

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    Migration

    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: Yes. At least some 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.

    Individuals may move hundreds of meters between summer and winter habitats (Matthews and Pope 1999).

    Matthews and Pope (1999) found that home range size was largest (53-9,807 square meters) in September. In the high Sierra Nevada, overland movements exceeding 66 meters were observed in 17 percent of tagged frogs; movement between lakes 1 kilometers apart was detected; 97 percent of tagged frogs wintered in the same lake in consecutive years (Pope and Matthews 2001).

    Seven of 20 frogs translocated 144-630 meters returned to their original capture site within 30 days; translocation was stressful (frogs lost body mass) (Matthews 2003).

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    Trophic Strategy

    Comments: Adults of the Rana muscosa/Rana sierrae complex eat aquatic and terrestrial invertebrates and anuran larvae; availability of larval anuran prey may be an important factor in distribution, body condition, and survival of adults (Pope and Matthews 2002). Larvae eat algae, organic debris, plant tissue, and minute organisms in water.

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    Population Biology

    Number of Occurrences

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

    Estimated Number of Occurrences: 6 - 20

    Comments: Vredenburg et al. (cited by Macey et al. 2001) stated that there are only 3-4 healthy populations in the southern Sierra Nevada.

    Historically, Rana muscosa was documented in approximately 166 localities in creeks and drainages in the mountains of southern California (Jennings and Hayes 1994). Currently the species is known from only seven or eight locations (Backlin et al. 2002, cited by USFWS 2002; Vredenburg et al. 2007).

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    Global Abundance

    50 - 2500 individuals

    Comments: Total adult population size is unknown but may not exceed a couple thousand (generously assuming 20 subpopulations averaging 100 adults); available information indicates fewer subpopulations and smaller subpopulation sizes. In southern California south of the Sierra Nevada, estimated population size in 2003 was around 183 adults (see USFWS 2006).

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    Life History and Behavior

    Cyclicity

    Comments: Inactive in cold temperatures. Primarily diurnal. Inactive 7-9 months each year at high elevations (Pope and Matthews 2002).

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    Reproduction

    Breeds: March-June at lower elevations; May-August at higher elevations. At high elevations, larvae require 2-3 summers to reach metamorphosis (Bradford 1991). Individuals become sexually mature 3-4 years following metamorphosis (Zweifel 1955).

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    Conservation

    Conservation Status

    IUCN Red List Assessment


    Red List Category
    EN
    Endangered

    Red List Criteria
    B2ab(ii,iv,v); C2a(i)

    Version
    3.1

    Year Assessed
    2008

    Assessor/s
    Geoffrey Hammerson

    Reviewer/s
    Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)

    Contributor/s

    Justification
    Listed as Endangered because of a drastic long-term and likely ongoing decline that has resulted in a very small current area of occupancy, severe population fragmentation, and small estimated population size.

    History
    • 2006
      Critically Endangered
      (IUCN 2006)
    • 2006
      Critically Endangered
    • 2004
      Vulnerable
    • 1996
      Vulnerable
      (Baillie and Groombridge 1996)
    • 1996
      Vulnerable
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    Current Listing Status Summary

    Status: Endangered
    Date Listed: 07/02/2002
    Lead Region:   California/Nevada Region (Region 8)   
    Where Listed: southern California DPS

    Status: Proposed Endangered
    Date Listed:
    Lead Region:   California/Nevada Region (Region 8)   
    Where Listed: U.S.A., frogs occuring north of the Tehachapi Mountains


    For most current information and documents related to the conservation status and management of Rana muscosa , see its USFWS Species Profile

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    National NatureServe Conservation Status

    United States

    Rounded National Status Rank: N2 - Imperiled

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    NatureServe Conservation Status

    Rounded Global Status Rank: G2 - Imperiled

    Reasons: Occurs in the southern Sierra Nevada and mountains of southern California; numerous population declines and local extirpations have occurred and are ongoing, some in apparently pristine habitats; introduced trouts are a major factor in the decline; disease, recreational activities, airborne agrochemicals, and other factors also may be influential.

    Intrinsic Vulnerability: Moderately vulnerable

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    Population

    Population
    Vredenburg et al. (cited by Macey et al. 2001) stated that there are only 3-4 healthy populations in the southern Sierra Nevada.

    Historically, Rana muscosa was documented in approximately 166 localities in creeks and drainages in the mountains of southern California (Jennings and Hayes 1994). Currently the species is known from only seven or eight locations (Backlin et al. 2002, cited by USFWS 2002; Vredenburg et al. 2007).

    Total adult population size is unknown but may not exceed a couple thousand (generously assuming 20 subpopulations averaging 100 adults); available information indicates fewer subpopulations and smaller subpopulation sizes. In southern California south of the Sierra Nevada, estimated population size in 2003 was around 183 adults (see USFWS 2006).

    A precipitous decline in Rana muscosa/Rana sierrae appears to have occurred over the past 3-4 decades (Bradford 1991; USFWS 1999; Vredenburg et al., in Lannoo 2005). For the Rana muscosa/Rana sierrae complex as a whole, Jennings and Hayes (1994) mapped many more extirpated populations than extant populations.

    Of the 79 historical R. muscosa sites studied by Vredenburg et al. (2007), only 3 sites contained frogs when revisited between 1995 and 2005 (96 percent extirpation rate). Rana muscosa probably has been extirpated from more than 99% of the historical range in southern California south of the Sierra Nevada (USFWS 2002).

    Declines likely are continuing, but the current rate of decline (past 10 years) is uncertain.

    Population Trend
    Decreasing
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    Life History, Abundance, Activity, and Special Behaviors

    Similar to R. sierrae, breeding begins soon after ice-melt or early in spring and can range from April at lower elevations to June and July in higher elevations (Wright and Wright 1949; Stebbins 1951; Zweifel 1955). Eggs are deposited underwater in clusters attached to rocks, gravel, and under banks, or to vegetation in streams or lakes (Wright and Wright 1949; Stebbins 1951; Zweifel 1955). Livezey and Wright (1945) report an average of 233 eggs per mass (n=6, range 100-350) for R. sierrae, but egg counts per egg mass appear similar for R. muscosa (Vredenburg, unpublished data). Eggs contain a vitelline capsule, and three gelatinous envelopes, all clear and transparent (see illustrations in Stebbins 2003). In laboratory breeding experiments egg hatching times ranged from 18-21+ days at temperatures ranging from 5-13.5 degrees C (Zweifel 1955).

    The length of the larval stage depends upon the elevation. At lower elevations where the summers are longer, tadpoles are able to grow to metamorphosis in a single season (Storer 1925). At higher elevations where the growing season can be as short as three months, tadpoles must overwinter at least once and may take two to four years of growth before they are large enough to transform (Wright and Wright 1949; Zweifel 1955).

    • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
    • Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.
    • Stebbins, R. C. (2003). Western Reptiles and Amphibians, Third Edition. Houghton Mifflin, Boston.
    • Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. (1998). "Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America." Proceedings of the National Academy of Sciences of the United States of America, 95(15), 9031-9036.
    • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
    • Jennings, M. R., and Hayes, M. P. (1994). ''Amphibian and reptile species of special concern in California.'' Final Report #8023 Submitted to the California Department of Fish and Game. California Department of Fish and Game, Sacramento, California..
    • Drost, C. A., and Fellers, G. M. (1996). "Collapse of a regional frog fauna in the Yosemite area of the California Sierra Nevada, USA." Conservation Biology, 10(2), 414-425.
    • Bradford, D. F. (1989). "Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California: implication of the negative effect of fish introductions." Copeia, 1989, 775-778.
    • Bradford, D. F. (1989). ''Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California USA: Implication of the negative effect of fish introductions.'' Copeia, 1989(3), 775-778.
    • Bradford, D. F., Tabatabai, F., and Graber, D. M. (1993). ''Isolation of remaining populations of the native frog, Rana muscosa, by introduced fishes in Sequoia and Kings Canyon National Parks, California.'' Conservation Biology, 7, 882-888.
    • Briggs, C. J., Knapp, R. A., and Vredenburg, V. T. (2010). ''Enzootic and epizootic dynamics of the chytrid fungal pathogen of amphibians.'' Proceedings of the National Academy of Sciences, 107(21), 9695-9700 .
    • Davidson, C. (2004). ''Declining downwind: Amphibian population declines in California and historical pesticide use.'' Ecological Applications, 14, 1892-1902.
    • Davidson, C., Shaffer, H. B., and Jennings, M. R. (2002). ''Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines.'' Conservation Biology, 16, 1588-1601.
    • Finlay, J. and Vredenburg, V. T. (2007). ''Introduced trout sever trophic connections between lakes and watersheds: consequences for a declining montane frog.'' Ecology, 88(9), 2187-2198.
    • Grinnell, J., and Storer, T. I. (1924). Animal Life in the Yosemite. University of California Press, Berkeley, California.
    • Knapp, R. A. and Matthews, F. (2000). ''Non-native fish introductions and the decline of the Mountain Yellow-legged Frog from within protected areas.'' Conservation Biology, 14(2), 428-439.
    • Knapp, R. A., Boiano, D. M., Vredenburg, V. T. (2007). ''Recovery of a declining amphibian (Mountain Yellow-legged Frog, Rana muscosa) following removal of non-native fish.'' Biological Conservation, 135, 11-20.
    • Knapp, R.A. (1996). ''Non-native trout in the natural lakes of the Sierra Nevada: an analysis of their distribution and impacts on native aquatic biota.'' Sierra Nevada Ecosystem Project, Final Report to Congress, Center for Water and Wildland Resources, University of California (Davis), Davis, California, 363-390.
    • Lewis, T. R. (2009). ''New population of mountain yellow-legged frog (Rana muscosa) discovered.'' Herpetological Bulletin, 108, 1-2.
    • Livezey, R. L., and Wright, A. H. (1945). ''Descriptions of four salientian eggs.'' American Midland Naturalist, 34, 701-706.
    • Rachowicz, L. J., Knapp, R. A., Morgan, J. A. T., Stice, M. J., Vredenburg, V. T., Parker, J. M., and Briggs, C. J. (2006). ''Emerging infectious disease as a proximate cause of amphibian mass mortality.'' Ecology, 87, 1671-1683.
    • Salzberg, A. (2009). ''Population of nearly extinct Mountain Yellow-legged Frog discovered.'' Herpetological Digest, 9, 4.
    • Vredenburg, V. T. (2004). ''Reversing introduced species effects: Experimental removal of introduced fish leads to rapid recovery of a declining frog.'' Proceedings of the National Academy of Sciences of the United States of America, 101, 7646-7650.
    • Vredenburg, V. T., (2007). ''Concordant molecular and phenotypic data delineate new taxonomy and conservation priorities for the endangered mountain yellow-legged frog (Ranidae: Rana muscosa).'' Journal of Zoology, 271, 361-374.
    • Vredenburg, V. T., Fellers, G., and Davidson, C. (2005). ''The mountain yellow-legged frog Rana muscosa (Camp 1917).'' Status and conservation of U.S. Amphibians. M. Lannoo, eds., University of California Press, Berkeley, 563-566.
    • Vredenburg, V. T., Knapp, R. A., Tunstall, T. S., and Briggs, C. J. (2010). ''Dynamics of an emerging disease drive large-scale amphibian population extinctions.'' Proceedings of the National Academy of Sciences, 107(21), 9689-9694.
    • Zweifel, R. G. (1955). ''Ecology, distribution, and systematics of frogs of the Rana boylei group.'' University of California Publications in Zoology, 54, 207-292.
    • Voyles, J., Vredenburg, V. T., Tunstall, T. S., Parker, J. M., Briggs, C. J., and Rosenblum, E. B. (2012). ''Pathophysiology in mountain yellow-legged frogs (Rana muscosa) during a chytridiomycosis outbreak .'' PLoS ONE, 7(4), e35374. doi:10.1371/journal.pone.0035374.
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    Global Short Term Trend: Decline of 10-30%

    Comments: Declines likely are continuing, but the current rate of decline (past 10 years) is uncertain.

    Global Long Term Trend: Decline of >90%

    Comments: A precipitous decline in Rana muscosa/Rana sierrae appears to have occurred over the past 3-4 decades (Bradford 1991; USFWS 1999; Vredenburg et al., in Lannoo 2005). For the Rana muscosa/Rana sierrae complex as a whole, Jennings and Hayes (1994) mapped many more extirpated populations than extant populations.

    Of the 79 historical R. muscosa sites studied by Vredenburg et al. (2007), only 3 sites contained frogs when revisited between 1995 and 2005 (96 percent extirpation rate). Rana muscosa probably has been extirpated from more than 99% of the historical range in southern California south of the Sierra Nevada (USFWS 2002).

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    Threats

    Major Threats
    A petition to list the Rana muscosa/Rana sierrae complex as endangered cited the following threats: non-native fish introductions, contaminant introductions, livestock grazing, acidification from atmospheric deposition, nitrate deposition, ultraviolet radiation, drought, disease, and other factors (see USFWS 2000).

    Extensive surveys in the Sierra Nevada clearly demonstrate the strong detrimental impact of introduced trouts on R. muscosa/Rana sierrae populations (Bradford 1989, Knapp and Matthews 2000). Removal of non-native fishes (relatively easy in some Sierra Nevada lakes) might easily reverse the decline (Knapp and Matthews 2000).

    See Bradford (1991) for information on mass mortality and extinction of a population due at least in part to red-leg disease and predation on metamorphics by Brewer's blackbird; reestablishment of the extirpated population probably will be prevented through predation by introduced fishes.

    Frogs of the Rana muscosa/Rana sierrae complex are possibly but probably not threatened by sublethal effects of low pH and elevated levels of dissolved aluminum (Bradford et al. 1992).

    Fellers et al. (2001) documented oral chytridiomycosis (often indicated by oral disc abnormalities) in larvae and recently metamorphosed individuals of the Rana muscosa/Rana sierrae complex in the Sierra Nevada, where recent declines have occurred. However, loss of pigmentation of larval mouthparts does not always indicate chytridiomycosis (Batrachochytrium infection) (Rachowicz 2002).

    Davidson et al. (2002) found support for the hypothesis that airborne agrochemicals have played a significant role in the decline of frogs of the Rana muscosa/Rana sierrae complex.

    Southern California south of the Sierra Nevada: Threatened by predation by introduced trout (remaining frog populations generally are in upstream areas with barriers to trout colonization), recreational suction dredging for gold, human activities at campgrounds and day-use areas, and usual problems associated with small population size and population isolation (e.g., fire, flood, or drought could extirpate small populations, with little chance of reestablishment due to poor connectivity of populations). Human use in and along streams can disrupt the development, survivorship, and recruitment of eggs, larvae, and adult frogs (Jennings 1995; Stewart, in litt. 1995) and can change the character of a stream and its bank and associated vegetation in ways that make whole sections of a stream less suitable for the species (see USFWS 2002). Dams and diversions on streams alter natural hydrologic flow and may negatively impact breeding and foraging habitat and further exacerbate the decline of populations in southern California. Predatory non-native bullfrogs are present in many areas formerly occupied by R. muscosa (USFWS 2002) and likely are incompatible with viable R. muscosa populations. Pathogenic chytrid fungus (attacks larval mouthparts) may be a threat (USFWS 2002). Release of toxic or hazardous materials into streams is a potential threat (Jennings 1995, Backlin et al. 2002, USFS 2002).
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    Degree of Threat: Very high - high

    Comments: A petition to list the Rana muscosa/Rana sierrae complex as endangered cited the following threats: non-native fish introductions, contaminant introductions, livestock grazing, acidification from atmospheric deposition, nitrate deposition, ultraviolet radiation, drought, disease, and other factors (see USFWS 2000).

    Extensive surveys in the Sierra Nevada clearly demonstrate the strong detrimental impact of introduced trouts on R. muscosa/Rana sierrae populations (Bradford 1989, Knapp and Matthews 2000). Removal of non-native fishes (relatively easy in some Sierra Nevada lakes) might easily reverse the decline (Knapp and Matthews 2000).

    See Bradford (1991) for information on mass mortality and extinction of a population due at least in part to red-leg disease and predation on metamorphics by Brewer's blackbird; reestablishment of the extirpated population probably will be prevented through predation by introduced fishes.

    Frogs of the Rana muscosa/Rana sierrae complex are possibly but probably not threatened by sublethal effects of low pH and elevated levels of dissolved aluminum (Bradford et al. 1992).

    Fellers et al. (2001) documented oral chytridiomycosis (often indicated by oral disc abnormalities) in larvae and recently metamorphosed individuals of the Rana muscosa/Rana sierrae complex in the Sierra Nevada, where recent declines have occurred. However, loss of pigmentation of larval mouthparts does not always indicate chytridiomycosis (Batrachochytrium infection) (Rachowicz 2002).

    Davidson et al. (2002) found support for the hypothesis that airborne agrochemicals have played a significant role in the decline of frogs of the Rana muscosa/Rana sierrae complex.

    Southern California south of the Sierra Nevada: Threatened by predation by introduced trout (remaining frog populations generally are in upstream areas with barriers to trout colonization), recreational suction dredging for gold, human activities at campgrounds and day-use areas, and usual problems associated with small population size and population isolation (e.g., fire, flood, or drought could extirpate small populations, with little chance of reestablishment due to poor connectivity of populations). Human use in and along streams can disrupt the development, survivorship, and recruitment of eggs, larvae, and adult frogs (Jennings 1995; Stewart, in litt. 1995) and can change the character of a stream and its bank and associated vegetation in ways that make whole sections of a stream less suitable for the species (see USFWS 2002). Dams and diversions on streams alter natural hydrologic flow and may negatively impact breeding and foraging habitat and further exacerbate the decline of populations in southern California. Predatory non-native bullfrogs are present in many areas formerly occupied by R. muscosa (USFWS 2002) and likely are incompatible with viable R. muscosa populations. Pathogenic chytrid fungus (attacks larval mouthparts) may be a threat (USFWS 2002). Release of toxic or hazardous materials into streams is a potential threat (Jennings 1995, Backlin et al. 2002, USFS 2002).

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    Life History, Abundance, Activity, and Special Behaviors

    Rana muscosa have declined dramatically despite the fact that most of the habitat is protected in National Parks and National Forest lands. A study that compared recent surveys (1995-2005) to historical localities (1899-1994; specimens from the Museum of Vertebrate Zoology and the California Academy of Sciences) found that 96.2% of populations had gone extinct, with only 3 remaining out of 79 resurveyed sites (Vredenburg et al. 2007).

    The two most important factors leading to declines in R. sierrae and R. muscosa are introduced predators and disease. Introduced trout prey on R. sierrae (Needham and Vestal, 1938; Mullally and Cunningham, 1956) and have been implicated in a number of studies as one of the sources of decline in both R. sierrae and R. muscosa (Bradford 1989; Bradford et al. 1993; Jennings 1994; Knapp 1996; Drost and Fellers 1996; Knapp and Matthews 2000). Whole lake field experiments have shown that when non-native trout are removed, both Rana sierrae and Rana muscosa populations rebound (Vredenburg 2004; Knapp et al. 2007). While it is clear that introduced trout negatively affect R. sierrae and R. muscosa mainly through predation on tadpoles, trout also compete for resources with adult frogs. A food web study that used stable isotopes to trace energy through food webs in Sierran lakes concluded that introduced trout are superior competitors and suppress the availability of large aquatic insects that make up a major portion of the diets of adult frogs (Finlay and Vredenburg 2007). Trout removal by the California Department of Fish and Game has reduced fish populations in the Little Rock Creek in the Angeles National Forest, resulting in increased numbers of Rana muscosa (Salzberg 2009; Lewis 2009).

    A lethal disease, chytridiomycosis, caused by an aquatic fungal pathogen Batrachochytrium dendrobatidis (Berger et al. 1998) has caused population extinctions in R. muscosa and R. sierrae in the Sierra Nevada (Rachowicz et al. 2006). Long-term studies reveal that infection intensity is key; once a critical threshold of Bd fungal infection is reached, death ensues (Vredenburg et al. 2010). Population extirpation is the most common outcome, but a few mountain yellow-legged frog (Rana sierrae and Rana muscosa) populations have survived in low numbers. Modeling shows that chytriodiomycosis outcome at the population level (extirpation vs. persistence) can result solely from density-dependent host-pathogen dynamics, which may hold for other wildlife diseases as well (Briggs et al. 2010).

    A new study conducted during an outbreak of chytridiomycosis in the Sierra Nevada has shown that electrolyte depletion (sodium and potassium) for heavily infected wild mountain yellow-legged frogs is even more extensive than studies done in captivity have suggested, and is accompanied by severe dehydration despite the frogs' aquatic environment (Voyles et al. 2012). See also the NSF commentary. In an effort to rescue the last surviving mountain yellow-legged frogs, the Vredenburg lab is treating adult frogs in the field with anti-fungal medication; frogs are bathed for five minutes daily over the course of a week (Lubick 2010). Electrolyte supplementation may also be a way to help save individual frogs (Voyles et al. 2012).

    Other possible causes for decline in R. muscosa include air pollution from pesticide drift (Davidson et al. 2002; Davidson 2004), UV-B radiation, and long term changes in weather patterns, especially concerning the severity and duration of droughts. Acidification from atmospheric deposition has been suggested as another cause, but Bradford et al. (1994) found no evidence to support this hypothesis.

    The San Diego's Institute for Conservation Research has instituted a captive breeding program for this species (Salzberg 2009; Lewis 2009). In 2006, tadpoles were rescued from a drying creek in the San Jacinto Wilderness and were reared in captivity (Salzberg 2009; Lewis 2009). In December 2008 a pair of these frogs laid a clutch of 200 eggs in captivity; only a handful of these eggs were fertile, due to the young parental age, and a single offspring has survived to maturity (Salzberg 2009; Lewis 2009). The most recent breeding season, however (December 2009-March 2010) was very successful and biologists have just reintroduced about 500 eggs into the wild, as of April 23, 2010, into deep permanent pools at the University of California Riverside’s James San Jacinto Mountains Reserve. Tadpoles that hatch from these eggs will take about two years to mature into adults. The adults are expected to stay within the reserve since they do not migrate. The tadpole rescue and frog breeding effort has been funded by Caltrans, as part of mitigation for emergency work necessary to stabilize a slope and reopen State Route 330 near Rana muscosa habitat in the San Bernardino Mountains (Salzberg 2009; Lewis 2009).

    • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
    • Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.
    • Stebbins, R. C. (2003). Western Reptiles and Amphibians, Third Edition. Houghton Mifflin, Boston.
    • Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. (1998). "Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America." Proceedings of the National Academy of Sciences of the United States of America, 95(15), 9031-9036.
    • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
    • Jennings, M. R., and Hayes, M. P. (1994). ''Amphibian and reptile species of special concern in California.'' Final Report #8023 Submitted to the California Department of Fish and Game. California Department of Fish and Game, Sacramento, California..
    • Drost, C. A., and Fellers, G. M. (1996). "Collapse of a regional frog fauna in the Yosemite area of the California Sierra Nevada, USA." Conservation Biology, 10(2), 414-425.
    • Bradford, D. F. (1989). "Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California: implication of the negative effect of fish introductions." Copeia, 1989, 775-778.
    • Bradford, D. F. (1989). ''Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California USA: Implication of the negative effect of fish introductions.'' Copeia, 1989(3), 775-778.
    • Bradford, D. F., Tabatabai, F., and Graber, D. M. (1993). ''Isolation of remaining populations of the native frog, Rana muscosa, by introduced fishes in Sequoia and Kings Canyon National Parks, California.'' Conservation Biology, 7, 882-888.
    • Briggs, C. J., Knapp, R. A., and Vredenburg, V. T. (2010). ''Enzootic and epizootic dynamics of the chytrid fungal pathogen of amphibians.'' Proceedings of the National Academy of Sciences, 107(21), 9695-9700 .
    • Davidson, C. (2004). ''Declining downwind: Amphibian population declines in California and historical pesticide use.'' Ecological Applications, 14, 1892-1902.
    • Davidson, C., Shaffer, H. B., and Jennings, M. R. (2002). ''Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines.'' Conservation Biology, 16, 1588-1601.
    • Finlay, J. and Vredenburg, V. T. (2007). ''Introduced trout sever trophic connections between lakes and watersheds: consequences for a declining montane frog.'' Ecology, 88(9), 2187-2198.
    • Grinnell, J., and Storer, T. I. (1924). Animal Life in the Yosemite. University of California Press, Berkeley, California.
    • Knapp, R. A. and Matthews, F. (2000). ''Non-native fish introductions and the decline of the Mountain Yellow-legged Frog from within protected areas.'' Conservation Biology, 14(2), 428-439.
    • Knapp, R. A., Boiano, D. M., Vredenburg, V. T. (2007). ''Recovery of a declining amphibian (Mountain Yellow-legged Frog, Rana muscosa) following removal of non-native fish.'' Biological Conservation, 135, 11-20.
    • Knapp, R.A. (1996). ''Non-native trout in the natural lakes of the Sierra Nevada: an analysis of their distribution and impacts on native aquatic biota.'' Sierra Nevada Ecosystem Project, Final Report to Congress, Center for Water and Wildland Resources, University of California (Davis), Davis, California, 363-390.
    • Lewis, T. R. (2009). ''New population of mountain yellow-legged frog (Rana muscosa) discovered.'' Herpetological Bulletin, 108, 1-2.
    • Livezey, R. L., and Wright, A. H. (1945). ''Descriptions of four salientian eggs.'' American Midland Naturalist, 34, 701-706.
    • Rachowicz, L. J., Knapp, R. A., Morgan, J. A. T., Stice, M. J., Vredenburg, V. T., Parker, J. M., and Briggs, C. J. (2006). ''Emerging infectious disease as a proximate cause of amphibian mass mortality.'' Ecology, 87, 1671-1683.
    • Salzberg, A. (2009). ''Population of nearly extinct Mountain Yellow-legged Frog discovered.'' Herpetological Digest, 9, 4.
    • Vredenburg, V. T. (2004). ''Reversing introduced species effects: Experimental removal of introduced fish leads to rapid recovery of a declining frog.'' Proceedings of the National Academy of Sciences of the United States of America, 101, 7646-7650.
    • Vredenburg, V. T., (2007). ''Concordant molecular and phenotypic data delineate new taxonomy and conservation priorities for the endangered mountain yellow-legged frog (Ranidae: Rana muscosa).'' Journal of Zoology, 271, 361-374.
    • Vredenburg, V. T., Fellers, G., and Davidson, C. (2005). ''The mountain yellow-legged frog Rana muscosa (Camp 1917).'' Status and conservation of U.S. Amphibians. M. Lannoo, eds., University of California Press, Berkeley, 563-566.
    • Vredenburg, V. T., Knapp, R. A., Tunstall, T. S., and Briggs, C. J. (2010). ''Dynamics of an emerging disease drive large-scale amphibian population extinctions.'' Proceedings of the National Academy of Sciences, 107(21), 9689-9694.
    • Zweifel, R. G. (1955). ''Ecology, distribution, and systematics of frogs of the Rana boylei group.'' University of California Publications in Zoology, 54, 207-292.
    • Voyles, J., Vredenburg, V. T., Tunstall, T. S., Parker, J. M., Briggs, C. J., and Rosenblum, E. B. (2012). ''Pathophysiology in mountain yellow-legged frogs (Rana muscosa) during a chytridiomycosis outbreak .'' PLoS ONE, 7(4), e35374. doi:10.1371/journal.pone.0035374.
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    Management

    Conservation Actions

    Conservation Actions
    All known populations and majority of habitat in southern California occur on lands managed by the U.S. Forest Service (USFWS 1999, 2002). Elsewhere, most occurrences are on lands administered by the U.S. Forest Service or U.S. National Park Service. Occurrence in protected, pristine areas does not ensure population persistence, due to threats from non-native fishes and disease.

    A total of 8,283 acres (33.5 square kilometers) of stream segments and riparian habitat in portions of Los Angeles, Riverside and San Bernardino counties have been designated as critical habitat for the southern California distinct population segment of mountain yellow-legged frog (USFWS 2006). Almost all of the areas proposed as critical habitat are managed by the U.S. Forest Service's Angeles National Forest (ANF) and San Bernardino National Forest (SBNF). A small amount of privately owned land (approximately 119 acres) are also included as critical habitat.
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    Restoration Potential: Rana muscosa/Rana sierrae populations that have been extirpated or reduced as a result of fish introduction can recover to predisturbance levels after fish disappear, if a nearby source population of frogs exists (Knapp et al. 2001). Several agencies (National Park Service, CDFG and U.S. Forest Service) have begun and/or planned recovery efforts involving removal of introduced fishes, and a number of populations have recovered (Vredenburg 2004).

    Preserve Selection and Design Considerations: Basins with a variety of deep lakes and shallow ponds may be the most appropriate reserves for this declining species (Pope and Matthews 2001).

    Management Requirements: Conservation recommendations for the southern California population include: (1) Installation of signage along trails adjacent to occupied areas to encourage the public to remain on designated trails; (2) removal of picnic equipment or campsites (barbeque pits, picnic tables) adjacent to occupied areas; (3) organization of workshops to educate campground permittees about this population; (4) acquisition of habitat within private inholdings; (5) assignment of additional patrols to prevent illegal suction dredge mining within the Sheep Mountain Wilderness Area of Angeles National Forest; and (6) relocation of a trail adjacent to an area within Little Rock Canyon (USFWS 2002).

    Translocation of adults in the Rana muscosa/Rana sierrae complex may not be an effective conservation tool; frogs may return to original capture site and are stressed by translocation (Matthews 2003).

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    Needs: Introductions of non-native fishes in lakes and ponds should be avoided.

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    Relevance to Humans and Ecosystems

    Risks

    Relation to Humans

    Mountain yellow-legged frogs (the amphibian species complex including Rana muscosa and Rana sierrae) were once the most common vertebrates in the high elevation Sierra Nevada. Documented historical accounts go back to the turn of the last century (1915) from surveys conducted by Joseph Grinnell and Tracy Storer (published in 1924) from the University of California's Museum of Vertebrate Zoology. Joseph Grinnell was instrumental in the foundation of Yosemite National Park, one of the crown jewels of the United States National Park Service.

    • Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
    • Stebbins, R.C. (1951). Amphibians of Western North America. University of California Press, Berkeley.
    • Stebbins, R. C. (2003). Western Reptiles and Amphibians, Third Edition. Houghton Mifflin, Boston.
    • Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. (1998). "Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America." Proceedings of the National Academy of Sciences of the United States of America, 95(15), 9031-9036.
    • Storer, T. I. (1925). "A synopsis of the amphibia of California." University of California Publications in Zoology, 27, 1-342.
    • Jennings, M. R., and Hayes, M. P. (1994). ''Amphibian and reptile species of special concern in California.'' Final Report #8023 Submitted to the California Department of Fish and Game. California Department of Fish and Game, Sacramento, California..
    • Drost, C. A., and Fellers, G. M. (1996). "Collapse of a regional frog fauna in the Yosemite area of the California Sierra Nevada, USA." Conservation Biology, 10(2), 414-425.
    • Bradford, D. F. (1989). "Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California: implication of the negative effect of fish introductions." Copeia, 1989, 775-778.
    • Bradford, D. F. (1989). ''Allotopic distribution of native frogs and introduced fishes in high Sierra Nevada lakes of California USA: Implication of the negative effect of fish introductions.'' Copeia, 1989(3), 775-778.
    • Bradford, D. F., Tabatabai, F., and Graber, D. M. (1993). ''Isolation of remaining populations of the native frog, Rana muscosa, by introduced fishes in Sequoia and Kings Canyon National Parks, California.'' Conservation Biology, 7, 882-888.
    • Briggs, C. J., Knapp, R. A., and Vredenburg, V. T. (2010). ''Enzootic and epizootic dynamics of the chytrid fungal pathogen of amphibians.'' Proceedings of the National Academy of Sciences, 107(21), 9695-9700 .
    • Davidson, C. (2004). ''Declining downwind: Amphibian population declines in California and historical pesticide use.'' Ecological Applications, 14, 1892-1902.
    • Davidson, C., Shaffer, H. B., and Jennings, M. R. (2002). ''Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines.'' Conservation Biology, 16, 1588-1601.
    • Finlay, J. and Vredenburg, V. T. (2007). ''Introduced trout sever trophic connections between lakes and watersheds: consequences for a declining montane frog.'' Ecology, 88(9), 2187-2198.
    • Grinnell, J., and Storer, T. I. (1924). Animal Life in the Yosemite. University of California Press, Berkeley, California.
    • Knapp, R. A. and Matthews, F. (2000). ''Non-native fish introductions and the decline of the Mountain Yellow-legged Frog from within protected areas.'' Conservation Biology, 14(2), 428-439.
    • Knapp, R. A., Boiano, D. M., Vredenburg, V. T. (2007). ''Recovery of a declining amphibian (Mountain Yellow-legged Frog, Rana muscosa) following removal of non-native fish.'' Biological Conservation, 135, 11-20.
    • Knapp, R.A. (1996). ''Non-native trout in the natural lakes of the Sierra Nevada: an analysis of their distribution and impacts on native aquatic biota.'' Sierra Nevada Ecosystem Project, Final Report to Congress, Center for Water and Wildland Resources, University of California (Davis), Davis, California, 363-390.
    • Lewis, T. R. (2009). ''New population of mountain yellow-legged frog (Rana muscosa) discovered.'' Herpetological Bulletin, 108, 1-2.
    • Livezey, R. L., and Wright, A. H. (1945). ''Descriptions of four salientian eggs.'' American Midland Naturalist, 34, 701-706.
    • Rachowicz, L. J., Knapp, R. A., Morgan, J. A. T., Stice, M. J., Vredenburg, V. T., Parker, J. M., and Briggs, C. J. (2006). ''Emerging infectious disease as a proximate cause of amphibian mass mortality.'' Ecology, 87, 1671-1683.
    • Salzberg, A. (2009). ''Population of nearly extinct Mountain Yellow-legged Frog discovered.'' Herpetological Digest, 9, 4.
    • Vredenburg, V. T. (2004). ''Reversing introduced species effects: Experimental removal of introduced fish leads to rapid recovery of a declining frog.'' Proceedings of the National Academy of Sciences of the United States of America, 101, 7646-7650.
    • Vredenburg, V. T., (2007). ''Concordant molecular and phenotypic data delineate new taxonomy and conservation priorities for the endangered mountain yellow-legged frog (Ranidae: Rana muscosa).'' Journal of Zoology, 271, 361-374.
    • Vredenburg, V. T., Fellers, G., and Davidson, C. (2005). ''The mountain yellow-legged frog Rana muscosa (Camp 1917).'' Status and conservation of U.S. Amphibians. M. Lannoo, eds., University of California Press, Berkeley, 563-566.
    • Vredenburg, V. T., Knapp, R. A., Tunstall, T. S., and Briggs, C. J. (2010). ''Dynamics of an emerging disease drive large-scale amphibian population extinctions.'' Proceedings of the National Academy of Sciences, 107(21), 9689-9694.
    • Zweifel, R. G. (1955). ''Ecology, distribution, and systematics of frogs of the Rana boylei group.'' University of California Publications in Zoology, 54, 207-292.
    • Voyles, J., Vredenburg, V. T., Tunstall, T. S., Parker, J. M., Briggs, C. J., and Rosenblum, E. B. (2012). ''Pathophysiology in mountain yellow-legged frogs (Rana muscosa) during a chytridiomycosis outbreak .'' PLoS ONE, 7(4), e35374. doi:10.1371/journal.pone.0035374.
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    Wikipedia

    Mountain yellow-legged frog

    The mountain yellow-legged frog or southern mountain yellow-legged frog[1] (Rana muscosa) is a species of true frog endemic to California in the United States. It occurs in the mountain ranges of Southern California up to the southern Sierra Nevada. It is a federally listed endangered species.[2]

    Rana muscosa in the northern Sierra Nevada have been redescribed as a new species, Rana sierrae, the Sierra Nevada yellow-legged frog. This is a proposed endangered species as of 2013.[2] The mountains separating the headwaters of the South Fork and Middle Fork of the Kings River mark the boundary between the ranges of the two species.[1]

    Description[edit]

    Rana muscosa is 4 to 8.9 centimeters long. Its color and patterning are variable. It is yellowish, brownish, or olive with black and brown markings. Its species name muscosa is from the Latin meaning "mossy" or "full of moss", inspired by its coloration. It may have light orange or yellow thighs. When handled, the frog emits an odor reminiscent of garlic.[3]

    Habitat[edit]

    The frog occurs in mountain creeks, lakes and lakeshores, streams, and pools, preferring sunny areas. It rarely strays far from water. The tadpoles require a permanent water habitat for at least two years while they develop. The frog has been noted between about 1,214 and 7,546 feet (370 and 2,300 meters) in elevation in Southern California.[1]

    Biology[edit]

    The frog emerges from its wintering site soon after snowmelt. Its breeding season begins once the highest meltwater flow is over, around March through May in the southern part of its range, and up to July in higher mountains to the north. Fertilization is external and the egg cluster is secured to vegetation in a current, or sometimes left floating free in still waters. The juvenile may be a tadpole for 3 to 4 years before undergoing metamorphosis.[3]

    The frog lacks a vocal sac. Its call is raspy, rising at the end. During the day, it calls underwater.[3]

    This species feeds on insects such as beetles, ants, bees, wasps, flies, and dragonflies. It is also known to eat tadpoles.[3]

    Conservation status[edit]

    The frog is an endangered species under the US Endangered Species Act. The International Union for Conservation of Nature has listed it as endangered.[1] Its NatureServe conservation status is Imperiled.[4]

    Decline[edit]

    Mountain Yellow-Legged frog.jpg

    Once a common species, Rana muscosa was absent from much of its native range by the 1970s. Over the course of the last hundred years, 90% of its populations have been eliminated.[5] The frog was known from 166 locations in the Southern California mountains, and as of 2007, seven or eight remained.[1] The 2009 discovery of R. muscosa at two locations in the San Bernardino National Forest was newsworthy.[6] The frog is represented in the Sierra Nevada by three or four populations.[1] Its decline is attributed to many factors, including introduced species of fish such as trout, livestock grazing,[7] chytrid fungus,[8] and probably pesticides, drought, ultraviolet radiation.[7]

    Introduced fish species[edit]

    Trout were introduced to lakes and streams throughout the Sierra Nevada in the late 1800s to increase recreational fishing in the area. The fish feed on tadpoles, a main prey item. The introduced trout have changed the distribution of several native species in the local ecosystems.[5] After the removal of fish from several lakes, the frog reappeared and its populations increased.[5] It then began to disperse to other suitable habitats nearby.[9]

    Pesticides[edit]

    The decline of the frog from its historic range has been associated with pesticide drift from agricultural areas.[10][11] Frogs that have been reintroduced to water bodies cleared of fish have failed to survive, and analysis has isolated pesticides in their tissues.[12] Pesticides are considered by some authorities to be a greater threat to the frog than the trout.[13] The roles that pesticides and introduced fish play in frog declines is still debated, and the loss of R. muscosa has probably been influenced by multiple factors.[12]

    Chytridiomycosis[edit]

    Rana muscosa 3.jpg

    This species is one of many amphibians affected by the fungal disease chytridiomycosis. Ample research has explored the biology of the fungus and how to prevent related amphibian declines.[8] The fungus attacks keratinized areas of a frog's body. Tadpoles are not severely affected because only their jaw sheaths and tooth rows are heavily keratinized.[14] Infection in a tadpole can be identified by changes in the pigmentation of these parts.[15] Adults have keratin-rich skin and suffer worse infections.

    In studies, well adult frogs exposed to infected frogs for at least two weeks developed the disease. Transmission takes longer in tadpoles, generally over seven weeks.[15] Frogs may be predisposed to infection if their immune systems are weakened by other factors, such as pesticide.[16] Studies indicate that R. muscosa is naturally more susceptible to the chytrid fungus than many other frogs to begin with.[17]

    Conservation[edit]

    The first successful captive breeding of the frog occurred in 2009 when three tadpoles were reared at the San Diego Zoo. Conservation workers at the zoo plan to release any more surviving captive-bred frogs in the San Jacinto Mountains, part of their native range.[18]

    References[edit]

    1. ^ a b c d e f Hammerson, G. 2008. Rana muscosa. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. Downloaded on 05 August 2013.
    2. ^ a b Mountain yellow-legged frog (Rana muscosa). United States Fish and Wildlife Service.
    3. ^ a b c d Rana muscosa - Southern Mountain Yellow-legged Frog. California Herps: A Guide to the Amphibians and Reptiles of California. 2013.
    4. ^ Rana muscosa. NatureServe. 2012.
    5. ^ a b c Knapp, R. A., et al. (2007). Removal of nonnative fish results in population expansion of a declining amphibian (mountain yellow-legged frog, Rana muscosa). Biological Conservation 135(1), 11-20.
    6. ^ Nearly extinct California frog rediscovered. NBC News. July 24, 2009.
    7. ^ a b Vredenburg, V. The Mountain Yellow-legged Frog - Can They be Saved? Sierra Nature Notes Volume 1. January, 2001.
    8. ^ a b The Amphibian Chytrid Fungus and Chytridiomycosis. Amphibianark.org. Retrieved 04 August 2013.
    9. ^ Vredenburg, V. T. (2004). Reversing introduced species effects: experimental removal of introduced fish leads to rapid recovery of a declining frog. Proceedings of the National Academy of Sciences of the United States of America 101(20), 7646-50.
    10. ^ Davidson, C., et al. (2002). Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines. Conservation Biology 16(6), 1588-1601.
    11. ^ Davidson, C. (2004). Declining downwind: amphibian population declines in California and historical pesticide use. Ecological Applications 14(6), 1892-1902.
    12. ^ a b Davidson, C. and R. A. Knapp. (2007). Multiple stressors and amphibian declines: dual impacts of pesticides and fish on yellow-legged frogs. Ecological Applications 17(2), 587-97.
    13. ^ Taylor, S. K., et al. (1999). Effects of malathion on disease susceptibility in Woodhouse's toads. Journal of Wildlife Diseases 35(3), 536-41.
    14. ^ Andre, S. E., et al. (2008). Effect of temperature on host response to Batrachochytrium dendrobatidis infection in the mountain yellow-legged frog (Rana muscosa). Journal of Wildlife Diseases 44(3), 716-20.
    15. ^ a b Rachowicz, L. J. and V. T. Vredenburg. (2004). Transmission of Batrachochytrium dendrobatidis within and between amphibian life stages. Diseases of Aquatic Organisms 61, 75-83.
    16. ^ Rachowicz, L. J., et al. (2006). Emerging infectious disease as a proximate cause of amphibian mass mortality. Ecology 87(7), 1671-83.
    17. ^ Rollins-Smith, L. A., et al. (2006). Antimicrobial peptide defenses of the mountain yellow-legged frog (Rana muscosa). Developmental & Comparative Immunology 30(9), 831-42.
    18. ^ Mountain Yellow-legged Frog Hopping for Survival. San Diego Zoo Global.

    Further reading[edit]

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    Names and Taxonomy

    Taxonomy

    Comments: Yellow-legged frog populations now recognized as Rana sierrae formerly were included in Rana muscosa. Vredenburg et al. (2007) examined phylogeography of Rana muscosa as defined by Stebbins (2003) and determined that R. muscosa occurs in the southern Sierra Nevada and in mountains to the south and that populations in the Sierra Nevada north of this range comprise a distinct species (Rana sierrae).

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