Matsudodon: Otterly Perplexing

In 1973, there was a brief, but prolific spate of sightings of a mysterious, seal-like creature in the Edo river of Japan.

The creature was described as being around 2 meters long and resembling a seal, only with longer limbs and more pronounced claws. The animal was said to have a certain cat-like appearance to its facial features, and witnesses described the animal as being like a “cat that looked like a seal,” more than the other way around. It was even reported to make a sound like a yowling cat.

The creature was first sighted near a floodgate located along the Edo River near Matsudo, in Chiba prefecture, Japan, which is directly adjacent to Tokyo. Since the first sighting, the mysterious creature was 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 lot of speculation over what it could possibly be.

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.

One of the last known taxidermy specimens of Zalophus japonicus. (Read more insights about the Japanese sea lion from Brent Swancer, here.)

Eventually, the list of possible culprits expanded. The possibility of very large grass carp was 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. No, I am not making this up.

Perhaps, 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. And hey, they could have been swimming in a line.

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.

Interestingly, the Japanese River Otter is thought by some in cryptozoological circles here in Japan to be an explanation behind the sightings of another (an – otter?) Japanese cryptid, the legendary Kappa.

An otter view of the Japanese river otter (also Lutra lutra whiteleyi; Japanese: 日本獺, 日本川獺 nihonkawauso or nipponkawauso).

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?

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.

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?

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.

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Loren Coleman About Loren Coleman
Loren Coleman is one of the world’s leading cryptozoologists, some say “the” leading living cryptozoologist. Certainly, he is acknowledged as the current living American researcher and writer who has most popularized cryptozoology in the late 20th and early 21st centuries. Starting his fieldwork and investigations in 1960, after traveling and trekking extensively in pursuit of cryptozoological mysteries, Coleman began writing to share his experiences in 1969. An honorary member of Ivan T. Sanderson’s Society for the Investigation of the Unexplained in the 1970s, Coleman has been bestowed with similar honorary memberships of the North Idaho College Cryptozoology Club in 1983, and in subsequent years, that of the British Columbia Scientific Cryptozoology Club, CryptoSafari International, and other international organizations. He was also a Life Member and Benefactor of the International Society of Cryptozoology (now-defunct). Loren Coleman’s daily blog, as a member of the Cryptomundo Team, served as an ongoing avenue of communication for the ever-growing body of cryptozoo news from 2005 through 2013. He returned as an infrequent contributor beginning Halloween week of 2015. Coleman is the founder in 2003, and current director of the International Cryptozoology Museum in Portland, Maine.

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