The Greenland Sleeper Shark — Somniosus microcephalus — is a rather large, and strange, species of shark native to the icy waters of the North Atlantic, and is especially common in the region around Iceland and Greenland. The species has also been dubbed: the sleeper shark, ground shark, grey shark, gurry shark, and the Inuit name for it is Eqalussuaq. They are the most-northerly shark species currently alive, and are well adapted to life in the frigid waters.
And something worth noting — they have often been found to have the remnants of polar bears, horses, and reindeer in their stomachs, after being caught. An individual was once caught which had a completely-intact reindeer, antlers and all, inside its belly.
As mentioned before, they are a rather strange species — they have very small fins, they sometimes possess a very dark blackish color, they occasionally feature spots or streaks along their bodies, and they are thought to have an extremely long lifespan — possibly living as long as several hundred years. They are also one of the largest living species of shark — growing to lengths of over 21 feet, and reaching weights of over 2200 lbs. Some particularly large specimens have been reported, one of which was measured as being 24 feet long and weighing 3100 lbs. Most individuals currently alive seem to be between 8-16 feet long, and somewhere around 800-900 lbs, this may simply be as a result of overfishing though — as they grow extremely slowly, and take a long time to mature. Another notable fact is that the females are typically the larger of the two sexes within the species.
The Greenland Sleeper Shark is relatively closely related to the Pacific sleeper shark — another very large shark in the family Somniosidae. The general appearance of the species is of a thickset animal with a short snout, relatively small eyes, and small fins — in a way, almost like a serpent. Indeed it’s often been suggested that the Greenland Sleeper Shark is perhaps the real identity of the sea-serpents and sea-monsters that have been periodically sighted throughout the seas of the Northern Atlantic. It’s also been suggested that the Loch Ness Monster is/was in fact a particularly large sleeper shark. Not a bad guess really, the origin of the unicorn legend elasmotherium calls to mind a unicorn about as much as the Greenland shark does the Loch Ness Monster.
While the above facts may make it seem as though the species is well-understood — in actuality, very little is known about the elusive species overall. An interesting fact that is known though, is that they utilize a rather peculiar means of feeding — employing a rolling motion of their jaw, when working on large carcasses. The upper jaw features rather-thin pointed teeth which anchor the meat/animal, the lower jaw, which is composed of broad interlocking teeth, then does the cutting. These lower teeth feature short, smooth cusps that point outward; and interestingly, the teeth in the two halves of the lower jaw are projected outwards in opposite directions of each other.
Wikipedia provides some more facts:
The Greenland shark is an apex predator mostly eating fish. Recorded fish prey have included smaller sharks, skates, squid, eels, herring, capelin, char, cod, redfish, sculpins, lumpfish, wolffish and flounders. However, it may also prey on marine mammals such as seals. Bite marks on dead seals at Sable Island, Nova Scotia and Hawarden suggest that this shark may be a major predator for them in the winter months. Since Greenland sharks are perhaps one of the slowest-swimming shark and attain a maximum swimming speed that is about half the maximum swimming speed of a typical seal, biologists have wondered how the sharks are able to predate the seals. Some evidence has been found that Greenland sharks search out seals and ambush them while they sleep.
The Greenland shark is also known to be a scavenger but to what extent carrion figures into the slow-moving fish’s stomach contents is unknown. It is known, however, that the species is attracted by the smell of rotting meat in the water. They often congregate in large numbers around fishing operations. The shark is colonized by the parasitic copepod Ommatokoita elongata that eats the shark’s corneal tissue. It has been reported that this parasite is bioluminescent and gives the shark a greenish glow around the eye when seen in dark waters but this has not been scientifically supported.
The shark occupies what tends to be a very deep environment seeking its preferable cold water (31 to 50 °F) habitat. It has been observed at a depth of 7,200 feet by a submersible investigating the wreck of the SS Central America. A specimen video-taped at 9,098 feet off the coast of Brazil on February 11, 2012 may have been a Greenland shark, but cannot be distinguished in the video from a southern sleeper shark or Pacific sleeper shark.
An interesting, and recent, discovery about the species is that the females give birth to live young — retaining the developing embryos within their bodies until birth. They usually give birth to a litter of about 10 pups, which are each a couple of feet in length at birth.
And for those interested — yes, you can actually eat the sharks. It takes a bit of work to make them edible and non-toxic though, your best bet is to go with the traditional Icelandic ways of preparing them — long fermentation. Boiling the meat multiple times, using freshwater every-time, will work though, if need be. The traditional Icelandic method — which produces Kæstur Hákarl — is to bury the meat boreal ground and overtime let it go through several cycles of freezing and thawing.
Without these treatments though, the meat of the Greenland Sleeper Shark is poisonous. Primarily as a result of the toxin trimethylamine oxide, “which, upon digestion, breaks down into trimethylamine, producing effects similar to extreme drunkenness.” It’s been observed that when sled dogs consume the meat that they eventually are unable to even stand up, because of the neurotoxins. The meat also contains high levels of urea — hence the smell of urine that the sharks tend to have.
There’s actually a couple of Inuit stories about that — “the legend says that an old woman washed her hair in urine and dried it with a cloth; the cloth blew into the ocean to become Skalugsuak.” My favorite one though, is the one that states that the shark owes its smell to the fact that it lives within the urine pot of the god Sedna, and was brought into existence as a helping spirit to those seeking vision.
The shark definitely gives off an interesting presence — the sort of animal where if you come across it in the wild on your own, is very interesting to meet.
Something worth noting — while the species isn’t considered to be dangerous to humans, some Inuit stories do mention the sharks intentionally attacking kayaks. There are no modern verified reports of the sharks eating people though.