Illustration of a Megalodon shark and great white shark shown for scale
Credit: © Christian Darkin, Science Source

Arriving at the tail end of a long de-bait, scientists have figured out what happened to the megalodons that used to swim in our oceans. Megalodons were the largest sharks that ever lived, reaching an estimated 52 feet (16 meters) long. Megalodon, which means big tooth, lived from about 17 million to 2 million years ago. The fate of the megalodon has stumped scientists and enthusiasts for ages. How did such a powerful and monstrous shark die out?

The megalodon was a powerful predator (hunting animal). Its jaws may have reached about 6 1/2 feet (2 meters) across. Scientists believe it had an exceptionally strong bite. Megalodon’s largest teeth measure about 7 inches (17 centimeters) along their edges. They rank as the largest shark teeth known. A new finding made a splash in the headlines, revealing just how this monster shark became extinct. Extinction occurs when every member of a species (kind) of living thing has died.

The great white shark, shown here, is one of the most dangerous sharks. It has many sharp, triangular teeth. The great white shark can grow to more than 21 feet (6.4 meters) in length.
Credit: © Shutterstock

A new study has shown that maybe those big teeth didn’t help these large predators out much. After studying zinc isotopes in fossils of teeth from great white sharks and megalodons, the scientists reported that great white sharks and megalodons competed for food. Zinc isotopes in teeth reveal where the animal lies on the food chain. When teeth have low levels of zinc, that means the animal is higher on the food chain. The great white shark and megalodon tooth fossils had the same range of zinc isotopes. The two sharks were not chums, they were biting into the same prey! In a feeding frenzy, the great white sharks won, leaving the great big megalodons hungry.

While the great white shark is one of the most dangerous sharks, they can only grow to a little more than 21 feet (6.4 meters) in length. So the megalodon had about 30 feet (9 meters) on them! Unlike most other sharks, great white sharks have warm blood and warm muscles. These characteristics make them faster and stronger than most other sharks. Great white sharks have sharp, triangular teeth with jagged edges. They can rip chunks of flesh from seals and sea lions, two of their favorite prey. It looks like baby shark beat out the bigger 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.

Greenland shark
Credit: © Julius Nielsen, University of Copenhagen

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.

March 8, 2013

Beaches on the coast of southern Florida were closed to swimmers this week as thousands of sharks were spotted in the waters near shore. The sharks are migrating north for summer, heading from Florida to North Carolina. This migration  takes them past the shores of many beaches frequented by tourists, including Palm Beach. Scientists estimate that there are approximately 15,000 sharks migrating–mostly blacktips (which grow to be about 5 feet, or 1.5 meters, long) and spinners (which grow to be about 10 feet, or 3 meters, long). The sharks swim about 200 yards (180 meters) out from the beach, but lifeguards closed the beaches for swimming as a safety precaution. Florida had 25 unprovoked shark attacks in 2012, although none were fatal.

The body of a shark. Sharks rarely threaten humans, but authorities will often close down beaches where sharks are sited as a precaution. (World Book illustration by Marion Pahl)

The shark migration is normal and happens every year, but it is usually earlier and does not affect beach season in Florida.  In 2013, the migration is happening during spring break for many schools. Spring break is one of Florida’s heaviest tourist seasons. Scientists are not certain why the migration is happening so late in 2013.

Additional World Book articles:

• Migration

• Shark