Man Eating River Monsters

Posted by: mystery_man on March 23rd, 2013

There are many mysterious monsters dwelling in the lakes and rivers of the world, but the ones that really intrigue and terrify us are the ones that are purported to attack humans. When a cryptid goes from an undiscovered organism to a man eater, it becomes not only a mystery, but a menace. It becomes something that not only lurks in the murky depths, but in our nightmares as well.

Stories of man eating creatures inhabiting the waterways of Japan have been around since the time of the samurai.  At an exhibition at the Kawasaki City Museum entitled “Japan’s Mythical Creatures- Accounts of Unidentified Organisms,” there was a curious old account from 1834 concerning a strange and terrifying animal lurking in a marshland near Tokyo, Japan. This 1834 account tells of a group of samurai who were digging a canal near the Inba Marsh in Chiba prefecture, Japan when they were ambushed by a vicious, seal-like monster. The creature was described as being 5 meters long, and looking like a large seal with a face like a monkey. Whatever it was turned out to be highly aggressive, and according to the account it savagely attacked and killed 12 of the samurai.

It is not known what became of the monster, and there are no details as to whether it was ultimately subdued, or if it escaped into the bloodied marsh.

This seems like a truly frightening and harrowing account. What sort of creature would, or could, kill 12 well armed samurai warriors? As bizarre as it may sound, there are other stories of river dwelling beasts attacking humans in Japan as well.

An unidentified river in Japan was once said to be inhabited by a population of strange creatures said to be 4 to 5 feet long, with a scaly, fish-like body and human looking hair on their heads. These bizarre beasts were said to be amphibious, and would come onto the banks of the river to engage in rowdy, boisterous behavior. The creatures were described as being very loud, filling the air with their barking cries.

They were also man killers. In addition to playing and fighting amongst themselves, the strange river creatures were said to be highly aggressive towards humans and would outright attack anyone who came near. It was said that anyone who came across these beasts was attacked and disemboweled, yet oddly the bodies were not eaten.

Is there any way these two reports might be linked somehow? And what sort of creatures could have been behind such horrific accounts?

The descriptions and size of the beasts seem to fit in somewhat with perhaps a type of pinniped. David Heppel, former curator of Molluscs at the Royal Museum of Scotland suggested that the boisterous river killers of the second case might perhaps be dramatic, embellished accounts of Northern fur seals (Callorhinus ursinus). These pinnipeds do inhabit northern Japanese waters, in the Sea of Okhotsk, and are known to breed in the Kuril and Sakhalin islands near Japan’s Hokkaido. Perhaps some of these animals made their way far south and ended up in the river somehow. The reports of the mystery beasts climbing onto shore and the loud, boisterous behavior certainly sounds like fur seals.

Northern fur seal

These animals could also account for the huge creature found in the Inba marsh. Male fur seals are quite large, attaining sizes of up to 2.1 meters (7 feet). An out of place large specimen could seem quite monstrous and mysterious to someone not accustomed to seeing one.

It would not be completely unusual for a pinniped to end up far from its normal habitat, and indeed this has happened in Japan before. In 2002, an out of place male Bearded Seal was sighted in the Tama River in Tokyo Japan. It was subsequently sighted by a large number of people and became a media sensation and somewhat of a celebrity at the time. Thousands of people would gather for a chance to catch a glimpse of the seal, which was nicknamed “Tama Chan” by the adoring public. Tama-Chan moved into other rivers of the area as well, where it became a regular sight.


The case of Tama-chan is remarkable in that the native habitat of Beaded Seals is typically much farther North, in Arctic waters. Tama-chan was so far out of its range that there was speculation as to whether it would even survive in a Tokyo river in the summertime. Tama- chan did survive, and seemed to take quite well to its’s new home, finally taking up a permanent residence in the Arakawa River.

Nobody is sure how Tama-chan ended up in a Tokyo river, but it illustrates the possibility of pinnipeds ending up far out of their range in places where you would not expect to find one. This could explain other mystery river creatures in Japan, such as the Matsudodon, a strange seal-like creature with a cat’s face that was sighted along Tokyo’s Edo River in the 70s.

If these old accounts of man eating river creatures are the result of out of place pinnipeds, we are still faced with a perplexing facet of the reports. Fur seals are not aggressive man-eaters, and pinnipeds in general are not typically dangerous to humans. It is certainly hard to imagine them attacking groups of samurai or disemboweling humans that got too close. Most species of pinniped are shy towards humans, and would be more inclined to escape than boldly attack. The aggressive behavior described in these accounts certainly raises an eyebrow.

Out of place pinnipeds or something else? Whatever the cause behind these old man-eater accounts, it certainly makes one think twice about taking a dip.

About mystery_man

4 Responses to “Man Eating River Monsters”

  1. dconstrukt responds:

    great story…

  2. Chupacabra Millie responds:

    Interesting. Maybe a presently extinct unknown variety of seal? It sounds like it may be. It’s a bit bigger than the standard seal, which is why I say extinct and unknown.

  3. PoeticsOfBigfoot responds:

    Wait, were they well-armed while digging a canal? A possible minor inconsistency, yes, but tiny details like that are how stories slowly change over time. you know, the Butterfly Effect and all that.

  4. corrick responds:

    As almost always, great stuff from the mystery-man

    When we look at historical testimony it’s just human nature to assume that the witnesses thought much like ourselves. Or that over the years that details have remained largely accurate. That is just not true.

    Fur seals as suggested by mystery-man as well as the now extinct Japenese sea lion are both reasonable explanations.

    Just step back into time a little. As if any samurai warrior would descibe any large unkown animal as anything other than bloodthirsty and dangerous.

    Thanks, mystery-man, your posts are invariably interesting and well-researched. If I was psychic I’d say you have a crypto-Japan book brewing.

Sorry. Comments have been closed.

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