Wrinkled Frog
(Rana rugosa)

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Wrinkled Frog

Picture of a wrinkled frog

 

Citation for image:  The photo of the Wrinkled Frog (Rana rugosa) was taken April 15, 2002 at Waihi Stream, tributary to Manoa Stream by William Flaxington; used with permission.


Citation for text (below):  Information on wrinkled frogs in Hawai'i was taken from an account written by Fred Kraus of the Bishop Museum, extracted from Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo.  
Physical Description
  • Usually dark brown to grayish brown; skin is warty and ridged (wrinkles); also has small black spots on belly
  • Produces mucus on skin with distinctive odor
  • One of the smallest of true frogs usually 5-6 cm (about 2 inches)
Feeding Behavior
  • Primarily eat insects, especially ants, arachnids, crustaceans 
  • Active both day and night but prefer warm, moist weather 
Why and When Introduced to Hawai'i
  • Native habitat is Japan, Korea, northeastern China, parts of Russia
  • Introduced from Japan to Hawai'i in 1895 or 1896 by Albert Koebele to control insects
  • First released on Oahu, reported in Maui in 1936, and then reported on Kauai and Big Island by 1953
  • Found near sea level to an elevation of ~1100 m in Big Island
Life cycle
  • Females deposit eggs in slow-moving water and lowland ponds (in Asia, wrinkled frogs breed in rice paddy fields) eggs are in loose clusters of 10-200 usually found among vegetation
  • Clutch size varies from 400-1300 eggs; females can spawn up to 3 times per year
  • Tadpoles appear 5 days after fertilization; metamorphoses depends on size of juveniles and may occur within a year of hatching; reach sexual maturity 1-2 years later
  • In wild, average lifespan is 4-5 years
Environmental Impact to Hawai'i
Although wrinkled frogs are found primarily in Asia, they are quite common and are of least concern of becoming endangered.  In Hawai'i, wrinkled frogs are numerous and  have been collected on Oahu, Maui, Kaui, and the Big Island but their precise numbers are not known. Their effect on native insects, fishes, and birds is unknown.