Monster Monday: Ye Olde Greenland Shark
September 5, 2016
The Greenland shark (Somniosus microcephalus) is an unusual fish. It normally lurks in the cold, deep waters of the Arctic and North Atlantic oceans, so people rarely meet these frightening creatures up close. It is the second largest carnivorous (meat-eating) shark in the world and the apex (top) predator in its habitat. Only the great white shark grows larger. The Greenland shark eats most everything—it has even been known to feed on careless reindeer and polar bears! Its flesh is poisonous, yet it is the main ingredient in an Icelandic snack. On top of all that, Greenland sharks can live to be centuries old.
Mud-colored and torpedo-shaped, Greenland sharks can reach an enormous 18 feet (5.5 meters) in length. These lethargic monsters swim slowly in their frigid habitat. (They are the only sharks that live entirely in such cold waters.) During the summer months, Greenland sharks swim down to the deepest, coldest waters of the ocean. During the winter months, they often lurk near the surface, near floating chunks of ice, where they stalk seals and other large mammals.
Greenland sharks are eating machines, and they are not picky. They’ll eat whatever is at hand, and they are not overly concerned with their meal’s freshness. Often more scavenger than predator, they readily feast on carrion (dead and decaying flesh). Greenland sharks have extremely poor eyesight, but they have a fantastic sense of smell, which is helpful in finding food—rotten or otherwise—in the murky depths. Many Greenland sharks are seen with parasitic copepods attached to their eyes. These copepods, tiny animals that form part of the ocean’s plankton, eat away at the shark’s corneas, sometimes leaving the fish sightless.
The flesh of the Greenland shark is toxic (poisonous). It reeks of urine from high concentrations of an ammonia-based chemical that enables the Greenland shark to withstand the cold and extreme pressure of its deep-sea habitat. For animals that consume the shark’s flesh raw, the chemical causes symptoms that resemble extreme drunkenness, including vomiting, poor muscular coordination, and uncontrollable twitching. Native residents of Greenland describe such victims as “shark sick,” and the sickness can be fatal. Yet, some Greenland sharks are caught to prepare as a snack called hákarl (HOW kuhr). The shark flesh is processed to remove toxins by leaving it to rot for several weeks. This stinky snack is said to be a delicacy in Iceland, while others politely say it is at best an acquired taste. Some people have labeled it the most disgusting food on Earth!
The Greenland shark is also the Methuselah of the animal world. (According to the Bible, an Old Testament character named Methuselah lived to be 969 years old.) Scientists have long known that Greenland sharks grow very slowly, less than half an inch (1 centimeter) per year. Such a slow rate of growth suggests an animal with a life span well beyond that of most vertebrates (animals with a backbone). Scientists have recently found that the Greenland shark’s life span likely exceeds 400 years! No other vertebrate is known to live so long.