Surprising sharks

Think all sharks are gigantic, toothy eating machines? Think again: With more than 500 species of sharks, you’re sure to meet a few that surprise you. For instance, some sharks have teeth so small that they can’t take a bite out of anything. Others are practically vegetarian! "You think you understand sharks, and then they do something that totally shocks you," says Lisa Natanson, a biologist who studies sharks for the National Oceanic and Atmospheric Administration. 

Lemon sharks: Fishy friends

Can’t wait to hang out with your BFF? Neither can these sharks. Young lemon sharks often stick together for protection, helping each other watch out for larger sharks and other predators. But scientists have learned that lemon sharks won’t befriend just anybody. “They prefer to spend time with sharks that they’ve met before instead of strangers,” says Clemency White, a researcher at the Bimini Biological Field Station in the Bahamas. The sharks hang out with the same friends for years, following each other or swimming next to each other. And when scientists studied the pups in a predator-free environment, these sharks still chose to swim together rather than alone. Maybe these fish need matching friendship bracelets.

Whale sharks: Gentle giants

A whale shark’s mouth is so wide that a 10-year-old kid could fit inside. But don’t worry: These sharks are mostly slurping up tiny shrimp like plankton about as small as a few grains of sand. Whale sharks feed by swimming slowly with their mouths open and filtering the tiny plants and animals out of the water. The largest fish in the world, whale sharks can be longer than a school bus and weigh 50,000 pounds—about four times as much as an African elephant. "They’re so big that not many animals are going to bother them," Natanson says. "So they tend to be very easygoing sharks."

Chain catsharks: Green glowers

Through your eyes, the chain catshark seems to have brownish-yellow skin with black chain-shaped markings. But to another chain catshark swimming 1,600 to 2,000 feet below the surface, the fish glows in the dark! Pigments in the sharks’ skin absorb the blue light in the ocean and reflect it as green. These sharks have special cells in their eyes—called receptors—to see it. Because the glow patterns are different for males and females, scientists think these shy sharks use this ability to attract mates. "In that deep, dark environment, the sharks need to be able to find each other," Natanson says.

Great white sharks: Picky eaters

Sure, great whites have 300 triangular teeth and the ability to smell a drop of blood in 25 gallons of water. But that doesn’t mean these top predators will chomp everything in their path. In fact, when great whites bite people, they usually release them. Scientists think it could be because humans aren’t on their menu, unlike seals, sea lions, and dolphins. "It’d be like if you picked up a drink thinking it’s soda, and it turned out to be coffee—bleh!" Natanson says. But it might also be that these curious sharks are just investigating a new object the only way they can: with their mouths!

Greenland sharks: Ocean oldies

If you think your grandpa is old, just wait until you meet this fish. A Greenland shark swimming through deep, freezing Arctic water today might have been born when George Washington became the first president of the United States! This shark species can live for nearly 300 years—and possibly as many as 500 years. That’s the longest of any vertebrate (an animal with a backbone). Experts are still trying to figure out how these sharks can survive so long, but they think their icy-cold habitat and seriously slow lifestyle (a Greenland shark’s heart beats only once every 12 seconds; yours beats about once a second) might have something to do with their seemingly non-stop birthday parties.

Bonnethead sharks: Salad snackers

Bonnethead sharks are leafy-green eating machines. In fact, seagrass can make up over half of the bonnetheads’ diet. Scientists aren’t sure if these coastal sharks are trying to snack on the plants, or if they accidentally get a side salad while scooping up shrimp, mollusks, and blue crabs hiding in the seagrass. Unlike almost all other sharks, which are carnivores and don’t eat plants, bonnetheads have a special digestive system that can absorb nutrients from greens. Hey, bonnethead—you have a leaf stuck in your teeth!

Spinner sharks: Airborne acrobats

Some sharks ambush their prey; others bump them before going in for a bite. But only one shark species flies: spinner sharks. These predators glide beneath a school of tuna or sardines, eyeing the tasty fish huddled together in a protective ball-like shape. With a burst of energy, the shark swims toward the surface with its mouth open, its slim body twirling through the water like a ballerina. Score! The shark nabs a fish—but the show’s not over yet. The shark’s momentum pushes it up to 20 feet out of the water, rotating several times before splashing back down. Now that’s a fin-tastic show!

Text from the June / July 2020 issue of National Geographic Kids magazine.