Whale shark (2024)

A whale shark the size of a school bus swims slowly near the surface of the ocean. Its wide mouth is open, like an enormous net scooping up whatever happens to be around—mostly small fish, fish eggs, and plants. As the world’s largest fish, this won’t be a short trip—a whale shark needs to travel about 5,000 miles each year to find enough food.

Filter feeding

Whale sharks spend nearly eight hours a day gulping around 10,000 gallons of ocean water. At nearly 40 feet long, they seem like they could eat whatever they want. But they’re really after plankton—microscopic plants and animals.

The opening of whale shark’s throat is covered with about 20 giant pads that have hundreds of tiny holes. As the seawater goes in, these pads filter out the food, sort of like a colander catching spaghetti while the cooking water drains out. Then the water escapes through the shark’s gills, and the food is pushed down its throat.

Scientists have also observed whale sharks eat while “standing up” in areas with a lot of prey, like large schools of anchovies or other small fish. With its tail pointed toward the ocean floor and its mouth toward the surface, the shark opens and closes its massive four-foot-wide mouth to create suction. The pressure pulls in the surrounding water—along with the fish.

Gentle giants

Although whale sharks are the third biggest creature in the ocean (after blue whales and fin whales), they’re not aggressive and don’t threaten humans. In fact, researchers and divers often swim right next to them, and the sharks don’t mind a bit.

Whale sharks mostly swim and feed alone, but scientists have observed them hunting with other species of fish between March and August in western Australia’s Ningaloo Reef. That’s when whale sharks as well as predators like tuna, other sharks, and even birds arrive for a plankton buffet caused by coral spawning and egg laying.

Smaller fish try to avoid the predators by swimming in a big ball for protection. That might work against some predators, but the massive-mouthed whale sharks easily gulp up the fish.

Spot ’em

Each whale shark has a unique pattern of spots and stripes, sort of like your fingerprints. These patterns help scientists keep track of their movements as they migrate through tropical waters, including along the coasts of South Africa, Western Australia, Thailand, and Mexico.

Like all sharks, whale sharks don’t have bones. Their skeletons are made of cartilage—the same stuff found in human ears and noses. Cartilage is strong, flexible, and less dense than bone, so it helps sharks swim fast and use less energy.

Preserving populations

Adult whale sharks have no known natural predators, though blue marlin and blue sharks prey on younger ones.

Humans are the biggest threat to these endangered fish, which are illegally hunted and sold as food and can be injured by large shipping vessels. (Although their rubbery skin can be more than five inches thick, whale sharks can still be injured when fishing boats crash into them.) Their ocean habitat is also threatened by pollution.

But thanks in part to protected areas, where it’s against the law to harm whale sharks, scientists hope to see their numbers to rise. These protected regions include Australia, India, the Philippines, and the United States.

Scientists are also tagging and tracking the giant fish to learn more about their migration and breeding habits. Learning about whale sharks is an important part of protecting them. (Find out how you can help save oceans.)

Meet more surprising sharks in this story from National Geographic Kids magazine.