The Sound Of Cows In The Marsh Echoes The Impermanence

Today I would like to share the history of a species called “bullfrog”. They are very large frogs, 11-18 cm (4-7 inch) and 500-600 grams (1.1-1.3 lb).


Photo by Brian Gratwicke, Lithobates catesbeianus - Bullfrog

Photo by Brian Gratwicke, Lithobates catesbeianus – Bullfrog


They are called “bullfrog” because they make sounds like bulls do.

If you walk near water places such as swamps, ponds, lakes, and also rice fields in Japan, you will be astonished by the sounds they make.

An American proverb says;

They asked a bullfrog, “Why do you croak all the time?” He replied, “I’m enchanted with my voice.”



The country of origin of bullfrogs is the US, more precisely, in southern and eastern parts of the United States and Canada. They have been widely introduced across other parts of North, Central and South America, Western Europe, and some parts of Asia. However, they have been considered to be an invasive species in their new lands as their lifestyle are too aggressive. They behave like kings of the swamp and they eat as many insects, other amphibians, and even small birds. Moreover, they are extremely prolific. Thus, they may outcompete or have outcompeted native species and upset the peace, I mean ecological balance, in new lands.

But why have they been introduced into many places even though they are “risky” animals? Because they are “useful” for human beings. Bullfrogs serve human beings by being eaten and they are kept in breeding establishments.

You will notice how widely bullfrogs are distributed all over the world with this map. The area of the Natural range is in Red and the Introduced range is in Green.


Case of Japan

A dozen of bullfrogs were first brought into Japan from New Orleans, Louisiana, USA, in 1918, the year when World War I ended. This decision was made by a zoologist of a national university. He thought bullfrogs were useful for alimentation for Japanese people who needed animal protein to make their bodies as big and strong as those of westerners. They were also useful for farmers who needed a secondary job to increase their income.

The project of cultivation of bullfrogs was a success. Two years later from the introduction, the descendants of the first immigrant bullfrogs were distributed to many areas and the bullfrog cultivation became very popular all over in Japan. In fact, ten years later, in 1927, red swamp crawfish / Louisiana crawfish, or binomially called Procambarus_clarkii started to be imported from USA as the bait, especially for bullfrogs. However, problems occurred; bullfrogs did not achieve the popularity as food in Japan, and many of them escaped and went wild. In 1932, the situation changed. There was a high demand for frozen meat of bullfrogs in USA and bullfrogs started to go back home but processed and frozen. At that time, Japan had to gain foreign currency especially after World War II. Japan had worked as subcontractors of frozen bullfrog legs for money. So, bullfrogs did not serve directly for the alimentation to the Japanese but they enabled Japan to develop economically. Every year several hundred tons of bullfrogs were “produced” only for export.


This “happy” business of bullfrog cultivation was terminated abruptly in 1969, when an insecticide, BHC, was found from the frozen bullfrog legs processed in Japan. The bullfrogs engaged in an “occupation” were fired and went wild where old friends had been settling.

In 2005, Invasive Alien Species Act went into effect for the Prevention of Damage pertaining to the Ecosystem, etc. by Specified Foreign Organisms, and bullfrogs were specified in the following year after 88 years from their immigration. They did not come to Japan because they wanted to, but they were just brought to serve Japanese people.

Under the Invasive Alien Species Law, it is prohibited to keep them as a pet, to sell them, or to catch them for the purpose of other than exterminating them. But for academic or experimental purposes, they can be caught, sold, and kept. In fact, bullfrogs are frequently used for medical research, because their body systems are similar to higher animals. They are also dissected in many school biology classes so that students can learn animal anatomy.

For your information, red swamp crawfish which had been brought as food for bullfrogs were also specified as Invasive Alien Species…


Don't mess with me because you don't know the truth!! Photo by ericdege Procambarus clarkii (red swamp crawfish) ..at Cooper Creek (CC BY-NC 2.0)

Don’t mess with me because you don’t know the truth!!
Photo by ericdege Procambarus clarkii (red swamp crawfish) ..at Cooper Creek (CC BY-NC 2.0)


The sound of bullfrogs croaking in the marsh reminds me of a theory of impermanence. It is one of the essential ones in Buddhism which says that every conditioned existence, without exception, is transient, or in a constant state of flux.

It reminds me also of the opening lines of Heike Monogatari (The Tale of the Heike).

The sound of the Gion Shōja bells echoes the impermanence of all things; the color of the sāla flowers reveals the truth that the prosperous must decline. The proud do not endure, they are like a dream on a spring night; the mighty fall at last, they are as dust before the wind.
— Chapter 1.1, Helen Craig McCullough’s translation



Tonbo-numa (Swamp of Dragonflies) in Chiba, Japan
a swamp of habitat segregation, where bullfrogs are coexisting with dragonflies, smaller frogs, other insects and aquatic birds.


I have no idea at all if they are dreaming of their home country in the circumstances where they are hated or just “used”. Just imagine how a bullfrog will reply if you ask him, “why do you croak all the time?”

I think he will reply,

“We’ve been and will always be proud to be bullfrogs in any circumstances. Let it go. Let it go. Human beings will never bother us anyway.”

にほんブログ村 歴史ブログ 日本の伝統・文化へ
にほんブログ村 英語ブログ 英語の日記(和英併記)へ

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  1. Hilary より:

    Intersting, Rei! I walked past a small rice field near my place in Iwaki and often heard this giant belch of a grunt and thought it had to be a bull frog! It’s incredible how loud they sound. I never saw one, though. And I had no idea that they were imported!


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