Montane Brown Frog

R. ornativentris has a broad body. The canthus is blunt, and the tympanum is circular. This species has 3-7 vomerine teeth. The tips of the fingers and toes are blunt, and the webbing is well developed. The skin on the back of this species is slightly rough because of the small tubercles or granules. The mean snout to vent length for males is 48 mm (range 42-60), and for females it is 68 mm (range 36-78). There is a pair of vocal sacs and openings at the corners of the mouth. The males have a silver-gray colored throat and nuptial pads that are grayish brown.This species has a mating call that lasts 0.5 seconds with 5-6 distinct notes. The breeding period is between January and late June, generally in rice fields, small pools, and marshes. The food it eats includes insects, snails, earthworms, and slugs. R. ornativentris is karotypically unique because it only has 24 diploid chromosomes. 1,000-1,900 dark brown colored eggs are laid, which are 1.5-2.4 mm in diameter.

The species is found on the islands of Honshu, Shikoku, Kyushu, and Sado in Japan. R. ornativentris inhabits plains, hillsides, and mountainous regions that are up to 1,900 m.

The montane brown frog or Nikkō frog (Rana ornativentris) is a species of frog in the family Ranidae. It is endemic to Japan.

Its natural habitats are subtropical or tropical dry forests, rivers, swamps, freshwater marshes, arable land, irrigated land, and seasonally flooded agricultural land.