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Inviato da Wes von Papinešu on Luglio 13, 1999 at 17:42:20:
THE YOMIURI SHIMBUN (Tokyo, Japan) 13 July 99 Nature in short / In praise of our froggy friends (Kevin Short)
Frog and toad fans should set aside a day or two this summer for a trip out to the Natural History Museum and Institute, Chiba. The museum is running a special exhibition called "Kaeru no Kimochi," or "A Frog's Feelings." It examines frogs from a variety of perspectives, including ecology and conservation, but with a special emphasis on interactions between frogs and people.
Japan, with plentiful rainfall and various aquatic habitats, is home to a great number of frogs. Scientists to date have described 35 species, ranging from rare montane and island endemics to common toads and tree frogs that live in big city parks and gardens. A chunk of rice paddy countryside can contain six to seven species.
The Japanese people have been aware of their frogs for thousands of years. Frog bones have been excavated from archeological sites dating to the middle and late Jomon period (ca 10,000 B.C.-ca 300 B.C.). Images of frogs also appear on clay pots made during the same period.
About 2,000 years ago, the technology for paddy rice agriculture was imported from China and the Korean Peninsula. The paddies, as well as the shallow ponds and ditches that formed the irrigation system, provided new habitats for frogs. Over the centuries several species were able to adapt their breeding and life cycles to the rhythms of paddy agriculture. These became the countryside frogs familiar in song and story.
One interesting fairy tale is the "The Frog Returns a Favor" (Kaeru no Ongaeshi). A man comes upon a frog about to be swallowed by a snake. The man saves the frog, but the snake, seeking revenge, changes form into a human and marries the man's daughter. The snake-husband places a horrible spell on his bride, which causes her to fall ill. The man is beset with sadness and worry until one day a stranger appears at his door. The stranger informs the man that his daughter's sickness can be cured with an eagle's egg. The man sends his son-in-law out to fetch an egg. The eagle, however, is able to see that he is really a snake and carries him off in his talons. With the snake-husband dead, the spell is broken, and the girl regains her health. The stranger that appeared at the man's door was really the frog that he had saved from the snake.
This simple little fairy tale accurately portrays the important position of frogs in countryside food chains. Frogs feed mostly on insects, worms, spiders, centipedes and other small invertebrates. In turn, frogs fall frequent prey to larger predators such as snakes, weasels, egrets, herons, crows, shrikes and kingfishers. Snakes in turn are a favorite food of large hawks. In these food chains the frogs occupy the central position, forming a wide base linking the insects with the larger meat-eaters.
Perhaps because of the large number of frogs that inhabit the rice paddy countryside, they have captured the imagination of the Japanese.
One magnificent 19th-century painting displayed in the exhibition shows a beautiful kimono-clad woman intently watching a group of frogs engaged in a sumo match. A close inspection shows that many of the frogs, including the referees, are looking not at the battling wrestlers, but at the woman. Another historic painting depicts a battle with frogs, outfitted in full samurai regalia, as the combatants.
The idea of frogs battling and wrestling comes from watching males jostling one another during the mating season. The Japanese toad is especially well known for great brawls, called kaeru-gassen in Japanese, that take place among the mating males.
Unfortunately, the countryside frogs that have provided creative and artistic stimulation for thousands of years are now in imminent danger of being wiped out in many regions. Changes in the paddy irrigation system and loss of surrounding woodlands appear to be primarily responsible. A typical example displayed at the frog exhibition is the deep, vertical-sided concrete culverts that have replaced the traditional dirt irrigation ditches in many areas. These culverts are easy to maintain, but provide no habitat for frogs, and form a death trap for frogs, snakes, turtles and any other small animals that accidentally fall in and are unable to climb out.
The Natural History Museum and Institute, Chiba (Chiba Kenritsu Chuo Hakubutsukan) is located a short bus ride from JR or Keisei Chiba Station. Admission to the museum is free, but the special frog exhibition costs 500 yen for adults and 200 yen for children. The museum is open from 9 a.m. to 4:30 p.m. daily except Mondays. Call (043) 265-3111 for details. The frog exhibition runs until Sept. 5. Bring a picnic lunch or have a snack in the museum's coffee shop.
Be sure to set aside a whole day for your trip out to the Chiba museum. The museum's regular exhibit halls offer a full set of easy-to-understand displays covering the natural history of Chiba Prefecture. The exhibit halls start with geology, then take you on a fascinating journey through ecology, taxonomy and marine habitats into human history. The attached Ecology Park has botanical gardens that re-create the native vegetation of the prefecture, and an observation hut where you can watch birds and even huge bullfrogs.