Hatched tadpoles swimming to the surface from frogspawn. Photograph: Dorling Kindersley/Getty Images

Japan is no stranger to heavy downpours during the early summer rainy season.

But in recent days the proverbial "cats and dogs" have been joined by tadpoles, fish and the occasional frog.

Meteorologists admit they are bewildered by a spate of incidents in which the creatures appear to have fallen from the sky. People around the country have reported witnessing the phenomenon since the first sightings of stranded tadpoles were made in Ishikawa prefecture last week.

People living as far apart as Hiroshima in the south-west and Iwate in the north-east say they have stumbled on the dead creatures near their homes, in fields, school grounds, and on car roofs and windscreens.

In Ishikawa prefecture, on the Japan Sea coast, a resident found 13 crucian carp on and around his truck, each about 3cm long.

One popular theory is that the creatures were sucked up by waterspouts but meteorologists say no strong winds have been reported in the areas where tadpoles were found. One expert said gusts too weak to be picked up by observatories might have sucked up small quantities of water, along with a few unfortunate tadpoles. Ornithologists said it was too early too rule out their feathered friends.

Kimimasa Tokikuni, head of the Ishikawa branch of the Japanese Society for the Preservation of Birds, told the Yomiuri Shimbun that bigger birds, such as herons and black-tailed gulls, might have dropped the tadpoles after being disturbed in mid-flight.

But the startled bird theory fails to answer a simple question: why haven't the "flying" tadpoles been noticed before?

对日本来说，初夏雨季的倾盆大雨并不陌生。

但最近几天，谚语中的 “猫和狗”又加入了蝌蚪和鱼，偶尔还有青蛙。

气象学家表示他们对于一连串动物从天而降的现象也很迷惑。自从上周在石川县有市民第一次看到搁浅的蝌蚪，随后一直有民众报告说其目睹了这一现象。

家住远离西南部的广岛和东北部岩手县的人们说，他们偶然在家附近，田间，学校操场以及屋顶和汽车挡风玻璃上看到了死亡的动物。

在位于日本沿海地区的石川县，一居民在其卡车周围发现了13鲫鱼，每条约3厘米长。

一种目前流行的理论认为，是龙卷风将动物卷入空中，但气象学家说，在蝌蚪被发现的地区没有强风报告。 一位专家说阵风太弱以至于没有被天文台观测到，而阵风可能吸入了少量的水，还有一些不幸的蝌蚪。 鸟类学家说，现在排除鸟类还为时尚早。

日本鸟类保护联盟石川分盟负责人Kimimasa Tokikuni告诉《读卖新闻》，诸如苍鹭和黑尾鸥等大型鸟类，可能在下飞的的过程中受到惊吓将刚吃进腹中的蝌蚪吐出来。

但受惊鸟理论却没有回答一个简单的问题：为什么以前没有发现“飞行”的蝌蚪呢？