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Mountain Yellow-legged Frog (Rana muscosa) Fact Sheet: Behavior & Ecology

Activity Cycle

Daily activity

  • Diurnal

Seasonal activity

  • Migrate to suitable areas for reproduction, feeding, and over-wintering
  • Hibernation
    • Sierra Nevadas (Bradford 1984)
      • Hibernate underwater in lakes and streams
      • 6 to 9 months prior to the spring breeding season
    • Southern California
      • May hibernate in deep stream pools for up to 6 months (Santana 2015)
    • Active after snow melts and before winter freeze (Mathews and Pope 1999)
      • Both tadpoles and adults seek warmest thermal regions
      • Never far from water

Territory Size

Females

  • Average range of 462 yards2 (386 m2) in August
  • Average range of 6098 yards2 (5,099 m2) in September

Males

  • Male territory is much smaller
  • Between 87 and 98 yards2 (73 and 82 m2)

Behavior

Very aquatic frog species

  • Tadpoles hide under rocks and mud in ponds and lakes
  • Tadpoles obtain oxygen through skin, gills, and mouth
  • Underwater, adult frogs obtain oxygen through skin and mouth
  • Occupy shallow depressions at bottom of frozen lakes in winter
  • When threatened, will bury in substrate

Dormancy

  • Metabolic rate decreases significantly during dormancy
  • High mortality can occur with oxygen depletion (lakes that are frozen over contain less oxygen)
  • Tadpoles move to warmer waters in spring
    • Increases body temperature and metabolic rate, hastening development
  • Rising temperatures determine end of dormancy

Thermoregulation

Ectothermic

  • Like all amphibians, Rana muscosa is ectothermic or "cold-bodied" (external environment regulates body temperature)
  • Not usually in shade for longer than 20 minutes
  • Bask in sun to achieve high body temperatures
  • Body temperature is about 25°F warmer while basking in sun (vs. in shade)
  • Find warm micro-habitats next to shoreline
  • Move back and forth from water

Communication

Call is a short, raspy croak or clicking sound

Only male frogs make courtship calls

  • Call to attract a mate
  • Call to communicate to female that she is about to be mounted
  • Warning call to males
    • If about to be grasped by another male

Vocalize to defend territory

Calls made through vibration of vocal cords, as frog exhales

  • No vocal sacs present to further modify sounds (as in other frog species)

Locomotion

Migration to over-wintering habitat

  • Frogs move in short bursts of 2-5 hops (Mathews and Pope 1999)
    • Appear to rest between bursts
  • Fairly straight routes
    • Use shortest distance over dry land

Jumping

  • Forelimbs lift up, hind legs extend
    • Propels frog into the air, as hind feet roll off ground
  • Propelled at approximately a 45° angle
  • Forelimbs brace frog as it lands

Swimming

  • Hind legs extend backwards causing webbed toes to open
  • Webbing increases surface area of foot
    • Allows frog to use water as a launching pad
  • Frog is propelled upwards and forwards
  • Forelimbs held flat against body as frog swims

Interspecies Interactions

Predators of tadpoles

  • Trout: brown, golden, rainbow
    • Also eat eggs (Natalie Calatayud, personal communication, 2016)
  • Brook char

Predators of adults

  • Garter snakes
  • Brewer's Black Bird
  • Clark's Nutcracker (bird)
  • Raccoons
  • Coyotes

Can You Find the Tadpole?

Mountain Yellow-legged frog tadpole

Tadpole coloration provides excellent camouflage with leaf litter found at the bottom of creeks.

Image credit: © San Diego Zoo Global. All rights reserved.

Page Citations

Bradford (1984)
Camp (1915)
Halliday and Adler (1986)
Hutchinson and Dupre' (1992)
Hutchinson and Whitford (1966)
Jameson (1955)
Jennings and Hayes (1994)
Lemm (2006)
Mathews and Pope (1999)
Santana (2015)
USFWS (2002)
Vredenburg et al. (2008)
Zweifel (1955)

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