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A Mysterious River Monster in Japan

Sighted in the Edo River of Japan during the 1970s was a bizarre, seal-like creature most commonly reported as being around 7 feet in length, with a face like a cat, long arms ending in sharp claws, a somewhat elongated neck, sagging skin, a long thin tail, and a distinctive cat-like mewl or sometimes screech. The strange beast was seen exclusively in the year of 1973, when there was an intense wave of sightings in the portion of the river passing the city of Matsudo, in Chiba prefecture, and since it was a relatively urban area and apparently the thing was not shy at all it was seen hundreds of times. The creature was first sighted near a floodgate located along the Edo River and would go on to be spotted on many occasions by joggers and anglers along the riverside in the same general area. In all, eventually over 100 witnesses are said to have sighted the creature during a fairly short period in 1973. The animal became known as the Matsudodon, named after nearby Matsudo city, and it sparked a major news craze at the time. Nothing like it had ever been seen before in the river, and nothing like it has been seen since.

The Matsudodon was sighted frequently, and was not only apparently not afraid of being seen, but at times was downright bold, even playful. One fisherman out in a rowboat reported having seen the creature pop up from right below his boat, after which it circled him and rolled about in the water, almost as if it wanted to play, before suddenly diving down with a dramatic splash of its tail. The fisherman would report that he had had the distinct feeling that the beast was merely curious and non-threatening. On another occasion, a jogger claimed that he had seen the creature out in the river doing jumps and spinning in the water as if amusing itself, and another eyewitness allegedly saw it tossing about a piece of floating garbage as if it were a ball.

Matsudo City along the Edo River

The Matsudodon was sometimes seen by large groups of people, such as a crowd of curiosity seekers who gawked at it from a bridge as it leisurely cavorted in the water below and let out cat-like mewling noises. On another occasion a group of friends reported seeing the creature sunning itself out of the water on the riverside. Over the years I have been fortunate to investigate the area and talk to some of the locals who were actually there at the time, since I just so happen to live right there where it all happened and this is practically right in my backyard. Through some snooping around I have managed to collect a few reports of the mysterious animal that are curious at the very least.

One account was relayed personally to me by an elderly local, who claims that at the time she would actually go out to the river and toss it fish, which it would snap up with relish. According to this witness, the Matsudodon would come by every day at around the same time to receive these handouts, and would get rather close to shore. She said that at no point did it seem aggressive or scared, and she also stressed that it was not a seal of any kind, and that it could grasp and manipulate things with its “hands.” Another old local there at the time was an elderly fisherman, who to this day goes out to fish at the river nearly everyday and remembers that time well, although he says that at first he had been very skeptical of it all. He didn’t believe that the Matsudodon was anything other than a hoax or some sort of mass hysteria, that is until he saw it himself. He says:

I was sitting out there by the river, out on the shore by the floodgate at my usual spot on a clear and sunny day. I was just fishing, having a smoke, and lost in my thoughts. Suddenly, this head just popped up out of the water right in front of me only a few meters out. It looked sort of like the head of a cat, with whiskers and cat-like ears perked up on its head. Its eyes were very large and expressive and it just floated there staring at me. It didn’t blink at all, just stared. Then it dove under the water and I could see it was pretty big, maybe 2 meters long. It dove under and then came up again nearby with a fish in its mouth! It gave me a look almost like “good luck with your fishing!” then swallowed the fish and dove under again to disappear. I haven’t ever seen anything like it before or since. I didn’t doubt all the Matsudodon reports after that.

When I asked this witness whether he thought it might have been a seal or not, he was very sure that it was not, saying:

A seal? No way. The body was kind of like a seal, but that face, it was just like a cat. And seals don’t have ears perked up on their heads like that. There was also the fact that I’m pretty sure it had a prominent tail. The eyes were not those of a seal either. I don’t know what that thing was, but I can say it was not a seal.

Stretch of the Edo River where many of the sightings occurred

Another report I hunted down was from a long-time Matsudo resident who saw the creature in the early evening while out walking her dog along the river side back in 1973. She tells me that her dog suddenly became agitated and began growling and barking while looking out over the water. The witness peered through the coming twilight and that was when she saw something she could not explain. She says:

That’s when I heard a big splash. I thought it was just a fish jumping, but then I saw a dark hump moving through the water, getting closer to shore. My dog was barking and making quite a lot of noise at this point and as this shape came closer she turned from aggressive to scared, trying to pull the leash the other way. This shape got closer and then a head, very feline in appearance, very large eyes, came up out of the water and whatever this thing was let out a strange noise like a cross between a dog’s bark and a cat’s screech. It was actually a pretty horrible noise, and set my hair standing on end. My dog and I got out of there as quick as we could.

One other report was second hand, but still very curious. The lady I spoke with says that her daughter saw the creature while sitting out by the river one day. It apparently came up and floated on its back for a time, after which it seemed to start to come ashore before having second thoughts and going away. She says:

My daughter told me that this thing was just floating along on its back, and that it kind of reminded her of a very large sea otter in that respect. It had then rolled over and seemed to almost be about to come ashore when it seemed to sense it was being watched, looked in her direction as it was halfway up onto some rocks, and disappeared under the water. It apparently didn’t come up after that, and that was the last she saw of it.

What was this thing? The creature was only ever seen in the area of Matsudo and only for a brief span of time, leaving the impression that whatever it was it was probably only a passing visitor. Since the Edo River connects to Tokyo Bay it has been speculated that it could have been something that wandered in from the sea by accident and got lost, although what that could be is anyone’s guess. The most rational answer seems to be that a seal had somehow found its way up the river from the sea. This has happened before in Japan, most notably in the famous case of the seal that made its home for a time in the Tama River of Tokyo. “Tama-chan,” as the seal was affectionately known, became big news in Japan, grew to be somewhat of a celebrity, and drew large crowds of people trying to get a look at it. There have also been well publicized incidents of whales doing the very same thing. However, the cat-like appearance and sounds the Matsudodon was reported to make, as well as the longer limbs, don’t really fit in with seals or whales, and witnesses specifically insisted that what they had seen was no normal seal.

The Edo River at sunset

The possibility of very large grass carp has been suggested, but again, this fish has very little in common with what was described in reports. Experts who were consulted and didn’t scoff at the accounts suggested that the creature in question was an out of place muskrat or otter, or even otters swimming in a line. This is actually an interesting idea in some respects. An otter or muskrat would not be expected in this river and could surprise people, and their appearance could possibly produce some descriptions of the Matsudodon. Do otters or muskrats sound like a cat? No they do not. However, I recognize that when hearing a strange animal make a noise, one might be inclined to liken the sound to something more familiar. Since the Matsudodon was described as having a cat-like face, it seems possible that the sounds it made would be reported as “cat sounds,” I suppose. Neither otters nor muskrats approach 2 meters in length, but sizes could have been misjudged.

Since the sightings of the mystery creature stopped as suddenly as they began, there are only the original reports to go on and it seems that whatever the Matsudodon was, it was a one-off phenomenon. It is fairly obvious that whatever was seen in 1973, it was not a permanent resident of the area. Matsudo and its surrounding area is well developed, with several bridges spanning the Edo River that see a good amount of traffic. There are also many joggers, anglers, and people having picnics in this area, so any large creature living in the river would have undoubtedly been seen again by now. The Matsudodon must have travelled there from somewhere else. What I am curious about is from where, and just exactly what exactly it was.

Maybe Matsudodon could be chalked up to some kind of mass hysteria. So a muskrat, otter, or a wayward seal or whale. Case closed, right? Or is it? 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 animal in the same basic vicinity as the Matsudodon sighting flap of 1973. This 1834 account tells of 12 samurai who were killed by a vicious, seal-like monster as they were digging a canal near the Inba Marsh in Chiba prefecture, Japan. The creature was described as being 5 meters long, and looking like a large seal with a face like a monkey.

Part of the Inba Marsh

Note that the Inba Marsh is located in Chiba prefecture, which is where the area of the 1973 sightings is also located. Although the Matsudodon was not reported to be aggressive or 5 meters long, it was still large at 2 meters, and two different such strange occurrences of an apparent mystery pinniped from the same general area have me curious. Is there a connection between the creature from the 1834 report and the accounts of 1973? Is it possible that the Matsudodon of 1973 was a juvenile or different gender of whatever species allegedly killed those samurai in 1834? What sort of seal-like creature would attack and kill 12 samurai, anyway? Is this thing possibly somehow related to what was seen in the Matsudodon flap of sightings? Hard to say, but curious nevertheless.

I find myself wondering whether there could be an unknown sea creature that is occasionally making its way up the rivers of Japan. Is it possible that the creatures seen in both cases were not just regular seals, but some sort of unknown pinniped that got trapped in the river just as known species of seal have been known to do? Whatever these creatures were, and whether or not they are connected in any way, it is an interesting case. I highly doubt that the creature was a regular inhabitant of the river. The area is fairly well developed and the river flows through some quite urban areas, making it hard for something like this to hide for very long. The river is also not exactly a prime habitat for a large animal such as this, because though there are fish the river itself is rather polluted and dirty. However, where it came from originally or where it went is anyone’s guess, and the Matsudodon remains an inhabitant of a rather little known corner of Japanese cryptozoological history.