Otton frog

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Otton frog
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Anura
Family: Ranidae
Genus: Babina
Species: B. subaspera
Binomial name
Babina subaspera
(Barbour, 1908)

Rana subaspera Barbour, 1908

The Otton frog (Babina subaspera), is a species of frog in the family Ranidae. It is endemic to the islands of Amami Ōshima and Kakeromajima in the Ryukyu Islands, Japan. Its natural habitats are subtropical or tropical moist lowland forests, freshwater marshes, and intermittent freshwater marshes. Once considered a delicacy as a source of food, it is now threatened by habitat loss through deforestation, and predation by introduced mongooses.

It is one of only two species (the other being Babina holsti) to possess a "pseudothumb" on the forelimbs.[2]

Physiology and Morphology[edit]

The Otton frog has been denoted the 'Wolverine frog' due to hidden retractable claws, which are sharp and shoot out from under their thumbs. Both male and female Otton frogs have these claws, with male claws being typically longer than those of the females.

Like the five-fingered Hypsiboas rosenbergi frogs of Latin America, the Otton frog has five fingers.[3]


This rare frog uses it's switch-blade claws to fight and in mating. Although both sexes have claws, it appears that only the males use them. This lead researchers to conclude that they are used to anchor the female to the male during mating.[4]

During fighting, two male Otton frogs will wrestle each other until in an embrace. They will then impale their opponent on their retractable spikes.[4]


  1. ^ Yoshio Kaneko & Masafumi Matsui (2004). "Babina subaspera". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. Retrieved February 11, 2010. 
  2. ^ Masayoshi Tokita & Noriko Iwai (2010). "Development of the pseudothumb in frogs". Biology Letters. 6 (4): in press. doi:10.1098/rsbl.2009.1038. 
  3. ^ Briggs, Amy (2012-10-19). "The Deadly Thumbs of Japanese Flick Knife Frogs". National Geographic Society (blogs). Retrieved 2016-08-28. 
  4. ^ a b Iwai, N. (2013-02-01). "Morphology, function and evolution of the pseudothumb in the Otton frog". Journal of Zoology. 289 (2): 127–133. doi:10.1111/j.1469-7998.2012.00971.x. ISSN 1469-7998.