Blue Whale vs. Whale Shark: Comparing Two Giants

Written by Colby Maxwell
Updated: June 24, 2023
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When considering the “kings” of the ocean, two names that regularly pop up are the whale shark and the blue whale. These ocean giants are truly remarkable and have their own unique role in the ocean ecosystem. Although these species are rather different, they are similar in a few ways. Let’s compare both and learn why these magnificent animals are worthy of conservation, as well as our wonder. And of course, we’ll answer the question of which animal is bigger when pitting blue whales vs. whale sharks!

Blue Whale vs. Whale Shark: Which One Is Bigger?

When it comes to size, there is a clear winner: blue whales are significantly larger than whale sharks. In fact, blue whales are the largest animal on the planet, ocean, or land. Even more, they are possibly the largest animals to have ever lived on the planet. Looking through the fossil record, it seems reasonable that blue whales are larger than any dinosaur, fish, mammal, or bird that has ever lived.

How big are blue whales? Blue whales reach sizes beyond 100 feet and weigh up to 219 tons. For humans, these numbers are rather difficult to quantify. In length, you could fit 17 men end to end across it with some room to spare. Using other imagery, they are as long as three school buses lined up end to end. The longest blue whale ever to be recorded clocked in at a bit more than 110 feet long. When it comes to weight, the behemoths weigh as much as 30 elephants or nearly double that of the Statue of Liberty.

Although blue whales are massive, whale sharks aren’t anything to scoff at either. Blue whales hold the record for being the largest animals ever, but whale sharks are the largest fish species to live. The largest whale sharks on record reached 61.7 feet and weighed over 41,000 pounds. They are the largest living nonmammalian vertebrate, and seeing one swim past is truly breathtaking. For comparison, they are about the size of a large school bus.

The Evolution of Blue Whales and Whale Sharks

Blue Whale under water with sun light streaming down from the surface above

Blue Whale underwater with sunlight streaming down from the surface above

©Atomic Roderick/

Although they share the name ‘whale,’ the two are actually not related. Let’s talk about their classification, as well as their evolutionary history.

Blue whales are marine mammals that have likely been on the earth for 1.5 million years, although whales have been around for 50 million. They are the largest animals in history and primarily feed on krill, small crustaceans that live in the ocean. Filter feeders, blue whales swim through the water and suck in water, trapping their tiny food bits. This method of eating is known as filter-feeding and classifies the blue whale as a “baleen whale.” There are four subspecies of blue whales and a potential fifth that lives off the coast of Chile. They were present in oceans worldwide until they began to be hunted for their oil by whalers. Driven nearly to extinction, blue whales have made a comeback after the practice was banned in 1966. Currently, they are classified as endangered.

Whale sharks are ocean-dwelling fish that have likely been around (in some form) for 265 million years. They are the only living member of the Rhincodontidae family. They are filter feeders and one of only three known shark species to do so (alongside megamouth and basking sharks). Although it shares the name “whale” with the blue whale, the species isn’t related and is likely just a result of the large size.

What Do Whale Sharks and Blue Whales Eat To Get So Big?

Biggest Fish in the World: Whale Shark

Whale sharks and blue whales are both filter feeders with a similar diet.

©Rich Carey/

Blue whales and whale sharks are both filter feeders and have a similar diet.

The Diet of Blue Whales

Baleen whales, of which the blue whale is included, are a group of filter-feeder whales that feed using baleen structures. Baleen are keratinized structures that are similar to a bony hair mesh. Swimming along, a baleen whale will pull water into its mouth, close the baleen, and squeeze the water through it. Acting as a filter, the baleen captures the food and allows the water to escape. When only the food is left, the whale can swallow it without any water.

Blue whales’ diets are almost entirely krill-based. Krill are small crustaceans that cycle through the sea depths to the surface along a 24-hour water column. The whales follow the krill and use their baleen to capture it in their massive mouthfuls of water. Typically, blue whales “lunge feed,” swimming very fast at large densities of their food. They can take in 220 tons of water brimming with krill in a single mouthful. Blue whales eat 2,469 pounds of krill a day to maintain their caloric needs.

The Diet of Whale Sharks

Whale sharks are filter feeders as well, although their method is usually more passive. Using filter pads in their mouths, whale sharks swim through the ocean and allow water to pass through their mouths and gills. The filter pads act as kitchen sieves and trap microbes, crustaceans, algae, and plankton in their latticework of tubes. The water is then expelled through the gills, allowing the food to make its way back to the throat. Whale sharks will occasionally feed vertically, placing their head near the surface and bobbing up and down to catch the plankton near the top of the water.

Do Blue Whales and Whale Sharks Have Any Predators?

Single breaching orca

Killer whales are the only predators that hunt baby blue whales but occasionally eat juvenile whale sharks.

©Minette Layne / CC BY 2.0 – License

As the largest animal on earth and the largest extant fish species, respectively, blue whales and whale sharks have few natural predators. Still, they face environmental challenges that threaten their species as a whole.

Blue whales have only one real natural predator. Killer whales are the only animals large and smart enough to prey on blue whales, although they must attack baby blue whales as the adults are much too large. Aside from that, humans, boat strikes, and climate change are the real dangers to the blue whale.

Whale sharks are also only vulnerable when they are young. As babies, whale sharks are attacked and eaten by merlin, sharks, and other predatory fish. At birth, whale sharks are roughly two feet in length, but they grow quickly. Once they reach adulthood, however, humans and boat strikes are the real danger.

Where Do Blue Whales and Whale Sharks Live?

Baleen Whale Migration - Blue Whale Migration Map

Blue whales and whale sharks can be found almost everywhere, but both migrate to follow food and mate.


Blue whales were once widespread across the earth’s oceans until whaling reduced numbers drastically. Now, they are found in all oceans except the arctic. Most species migrate between summer and winter feeding grounds, but there are some species that stay stagnant.

Whale sharks are found in two major populations but can be found anywhere the water stays above 70 degrees. There is an Indian Ocean population that has 75% of the entire species, but they also live in the Atlantic and Pacific Oceans.

The photo featured at the top of this post is ©

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About the Author

Colby is a writer at A-Z Animals primarily covering outdoors, unique animal stories, and science news. Colby has been writing about science news and animals for five years and holds a bachelor's degree from SEU. A resident of NYC, you can find him camping, exploring, and telling everyone about what birds he saw at his local birdfeeder.

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