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Mountain Yellow-legged Frog (Rana muscosa) Fact Sheet: Reproduction & Development

Reproduction

Reaching sexual maturity

  • Females mature between 1.73 and 1.97 inches (44 and 50 mm) in length (Zweifel 1955)
  • First breeding at about 2 years of age

Breeding

  • At lower elevations, breeding occurs between April and May
  • Eggs laid late spring to early summer (Natalie Calatayud, personal communication, 2016)
    • Often laid on undersides of leaves or other horizontal structures

Life Stages

Egg (The Mountain Yellow Legged Frog Site 2015; Vredenburg 2005; Zweifel 1955)

  • Number of eggs: 40-300 per egg mass
    • Egg size about 1.9-2.3 mm
  • Time to hatch
    • Depends on environmental conditions
    • In the wild: not well-understood
    • In managed care: 5-6 weeks (Natalie Calatayud, peronsonal communication, 2016, citing Michelle Curtis and Nicole Gardner, personal communications, 2016)
    • Eggs hatch into free-living larvae
  • Timing of metamorphosis (time elapsing from fertilization of egg to frog)
      • At lower elevations: same season as eggs are laid
      • At higher elevations: usually occurs the next summer
        • May not occur until the fourth summer at the highest elevations

Tadpole

  • One of largest tadpoles of any North American frog
    • Up to 3 inches long
  • Produces mucous to anchor itself to plants
  • Feeds off residual yolk from yolk sac
  • Develops long tail, external gills, working mouth parts, and long digestive tract
  • Metamorphosis in the wild
    • May occur within 6 months, but may take up to 2-3 years, depending on environmental conditions
      • Most frog species only need one season
  • Metamorphosis in managed care
    • Occurs before winter
  • Metamorphosis: changes in body structure
    • Tadpole increases in size
    • Eyes more noticeable, mouth is wider
    • Hindlimbs and forelimbs develop
    • Tail becomes shorter; reabsorbed
    • Gills become smaller; fold of skin grows over external gills
      • Breathes exclusively through internal gills as external gills disappear
      • Lungs develop
        • Tadpole breathes by gulping air from surface
    • Young frog can move to land
    • Diet becomes carnivorous

Longevity

Lifespan in the wild

  • Approximately 14 years, from egg to mortality

A New Generation

female Mountain Yellow-legged frog and eggs

Female Mountain Yellow-Legged Frog (Rana muscosa) with eggs.

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


Mountain Yellow-legged frog tadpole

Development of a tadpole.

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

 

Page Citations

Zweifel (1955)
Livezey and Wright (1945)
Stebbins (1951)
Mathews and Miaud (2007)
Vredenburg (2005)
The Mountain Yellow Legged Frog Site

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