Description
Rana japonica has a slender body with a long narrow head. The average snout-vent length is 48 mm for males and 54 mm for females. Females are usually much larger than males.

The body color is usually reddish brown with sparse black bands on the limbs and lateral side of body. Distinct black bands are seen along the canthus and behind the eyes, surrounding the tympanum. Circular tympanum is about 4/5 of the eye diameter. The skin of the back is nearly smooth with a few dermal ridges on the side. Dorsalateral folds are clearly visible.

Webs are moderately developed. Males develop yellowish brown nupital pads during the breeding season. Neither males nor females have vocal sac or vocal opening. Mating call is clear and consists of ten to twenty notes. A single note lasts as long as 2 seconds.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (4 records).

Rana Japonica occurs in Honsyu, Shikoku, and Kyusyu in Japan and southern region of China. Within Japan, Rana Japonica inhabits mostly in hillsides and plains, and is rarely seen in mountain ranges.

Life History, Abundance, Activity, and Special Behaviors

The breeding season is January to March, the earliest of all frog species in mainland Japan. Rana Japonica migrates from hillside to the breeding sites. Spawning usually occurs in shallow still water of rice paddies or marshes. The water temperature in the breeding season is around five to ten degrees.

Occasionally, the breeding season of Rana Japonica overlaps with that of Rana ornativentris. However, interbreeding rarely occurs because of the distinctively different mating calls. Interbreeding does not result in hybrids, but is experimentally shown to cause male infertility.

The egg mass is shaped like a smashed ball, about 10 cm in diameter, and contains 500-3,000 eggs. The egg mass is deposited directly to the bottom of the spawning site. In some years, the water temperature drops rapidly and freezing kills developing embryos. Metamorphosis takes place between May and June. Half of the froglets becomes sexually mature by late October of the same year. The rest of the froglets mature in the following year.

After completion of egg-laying, mature R.japonica become dormant underneath the mud of the rice-paddies or streams. In May, they become active again and migrate back to the hillside or plains. It is not clear whether or not R.japonica hibernate during the winter months.

R.japonica prefer to feed on small animals, such as spiders, Diptera, Coleoptera and insect larvae.

Possible reasons for amphibian decline

General habitat alteration and loss
Urbanization

References

Maeda, N. and Matsui, M. (1990). Frogs and Toads of Japan, 2nd edition. Bun-Ichi Sogo Shuppan Co., Ltd., Tokyo, Japan.

Okada, Y. (1966). Fauna Japonica Anura. Tokyo Electrical Engineering College Press, Tokyo.

Species Account Citation: AmphibiaWeb 2005 Rana japonica: Japanese Brown Frog <https://amphibiaweb.org/species/5062> University of California, Berkeley, CA, USA. Accessed Nov 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Nov 2024.

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