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Asian Treefrogs: Rhacophoridae

Kinugasa Flying Frog (rhacophorus Arboreus): Species Accounts

Physical characteristics: Also known as the forest green treefrog or the Japanese treefrog, the Kinugasa flying frog may be a solid, limegreen color, dark green, or green with many reddish brown, brown, or black speckles. The reddish brown and brown speckles are outlined with black. The frog's back, head, and legs are rough and covered with small bumps, or tubercles. Whether solid or speckled, its underside is white or cream-colored, often with somewhat-faded, brown blotches on the chest and throat. They have two large eyes bulging from the sides of a rather flattened, but large head. The eyes, which are orange to brown, often have a noticeable dark band running between them. They also have a noticeable ridge on each side of the head, stretching from the end of the snout to the middle of the eye and continuing on the other side of the eye where it curves down toward the top of the shoulder. The snout narrows toward the front. The legs are slender, and the underside of the rear legs has black lines and blotches near the body. The front toes are slightly webbed, but the hind toes are fully webbed. The toes on all four feet are long and The home of the Kinugasa flying frog is in Honshu, the largest of the islands that make up Japan, as well as on a small island, called Sado, just to the northeast of Honshu. In addition, it has been introduced to two other areas in Japan. (Illustration by Brian Cressman. Reproduced by permission.) have very large, triangular-shaped pads on the tips. Females are larger than males. Females reach 2.3 to 3.2 inches (5.9 to 8.2 centimeters) from the tip of the snout to the end of the rump, while males grow to 1.7 to 2.4 inches (4.2 to 6.0 centimeters) in length.

Geographic range: Its home is in Honshu, the largest of the islands that make up Japan, as well as on a small island, called Sado, just to the northeast of Honshu. In addition, it has been introduced to two other areas in Japan.

Habitat: Although they can live in lowland forests, Kinugasa flying frogs usually prefer wooded locations high in the mountains, sometimes more than 6,560 feet (2,000 meters) above sea level. Tadpoles develop in the water of rice fields, marshes, and other wetland ponds.

Diet: Its diet is made up of insects.

Behavior and reproduction: Usually found in mountains, the Kinugasa flying frog sits among trees or under piles of leaves along the ground for much of the year. It sometimes also enters people's gardens and makes its home there. In the cold winters of this area of Japan, the frog finds a spot under a layer of moss or buried just under the ground and enters a state of deep sleep, called hibernation (high-bur-NAY-shun), until the weather warms again the following spring. The breeding season for this frog is about four months long, from April to July. The breeding season begins when males hop to the edge of a pool or wet rice field and start calling. Each male makes a similar call, which is two to six clicking noises followed by several lower clucks. After a female follows a call to a male, he climbs on her back, and she releases a fluid rather like the raw egg white from a chicken's egg. She then kicks the fluid with her feet, beating it into a foam. Sometimes the male helps her in whipping up the fluid. The longer the foam is beaten, the larger it grows. When it reaches an oblong shape about 3.5 inches (8.8 centimeters) wide and 4.7 inches (12.0 centimeters) long, she lays her eggs inside the frothy nest. As she does, the male adds his own fluid, which is filled with microscopic cells, called sperm. When the sperm combine with the eggs, the eggs can start to develop into young frogs. A female may lay three hundred to eight hundred eggs in the nest.

Sometimes, the mating pair is not alone. Other males may join in by beating up the foam and by adding their own sperm-filled fluid to the nest. In this way, the eggs in one nest may not all get sperm from the same male. When this happens, the young frogs from one nest may have different fathers. Once all the eggs are laid, the outside of the nest starts to dry into a hard shell. The shell protects the eggs from other animals that might want to eat them, and it also keeps the foam inside from drying out. The eggs eventually hatch into tadpoles inside the nest. By this time, the bottom of the nest becomes soft, and the tadpoles fall out, dropping into the water below. There, they continue their growth and turn into froglets.

Kinugasa flying frogs and people: In some ponds in Japan, the frogs have become a tourist attraction. Here, hundreds of male and female frogs arrive together to mate at night and during the day, and people come from miles away to watch this natural scene. Away from these busy ponds, people who live in the countryside also enjoy hearing smaller groups of males calling from rice fields and pools of water on summer nights.

Conservation status: This frog is quite common, and the IUCN lists it as being of Least Concern, which means it has no known threat of extinction and does not qualify for any of the "threatened" categories. It lives in numerous protected areas, and because some populations are tourist attractions, people keep a careful watch over them. ∎

Additional topics

Animal Life ResourceAmphibiansAsian Treefrogs: Rhacophoridae - Physical Characteristics, Habitat, Diet, Behavior And Reproduction, Conservation Status, Kinugasa Flying Frog (rhacophorus Arboreus): Species Accounts - GEOGRAPHIC RANGE, ASIAN TREEFROGS AND PEOPLE