The blue whale is far bigger than the whale shark. A typical blue whale is 80 to 100 feet long, while most whale sharks are 18 to 33 feet. The two are not related: the whale shark is the largest fish, and the blue whale is a mammal and the largest animal known to have lived.
Despite the name, a whale shark is a shark, not a whale. It breathes with gills and has a skeleton of cartilage. A blue whale breathes air through lungs, is warm-blooded, and nurses its calves with milk. They do share a lifestyle: both are giant filter feeders that eat small prey.
Whale Shark vs Blue Whale: Key Differences
| Feature | Whale shark | Blue whale |
|---|---|---|
| Animal group | Fish (cartilaginous shark) | Mammal (baleen whale) |
| Scientific name | Rhincodon typus | Balaenoptera musculus |
| Typical length | 18-33 ft | 80-100 ft |
| Longest reported | 61.7 ft (18.8 m) | about 110 ft (33 m) |
| Weight | about 20 tons for the largest (estimate) | up to about 330,000 lb (165 tons) |
| Breathing | Gills | Lungs and blowholes |
| Body temperature | Cold-blooded | Warm-blooded |
| Reproduction | Eggs hatch inside the mother, live pups | One calf at a time, nursed with milk |
| Main food | Plankton, krill, fish eggs, small fish | Almost entirely krill |
| Lifespan | Uncertain, estimated at 50 to 100+ years | About 80 to 90 years |
| IUCN status | Endangered | Endangered |
Size Comparison
The largest whale shark on record measured 61.7 feet (18.8 m). Most that scientists measure are far smaller, usually 18 to 33 feet, and they reach maturity at about 30 feet. Whale sharks are hard to weigh, so figures such as 20 tons for the largest are estimates. The mouth of a big whale shark can be roughly 5 feet wide.
NOAA Fisheries lists blue whales at up to about 110 feet and 330,000 pounds. The heaviest one ever weighed was 190 metric tons (418,878 pounds). Even the longest whale shark on record is a little more than half the length of the longest blue whale, and a typical adult blue whale is three to five times longer than a typical whale shark. The blue whale size comparison covers the numbers in more detail.
How They Are Built and How They Move
Whale sharks have large gill slits, a flat head with a very wide mouth near the front, and a pattern of pale spots and stripes on dark skin. The pattern is unique to each shark, much like a fingerprint. A shark's tail beats from side to side, while a whale's tail flukes move up and down.
Blue whales have a long, slim, blue-gray body with pale mottling, a broad head, and a small dorsal fin set far back. They have baleen plates instead of teeth and a throat pleated with grooves that expand during feeding. NOAA says blue whales usually travel at about 5 miles per hour and can burst past 20 miles per hour.
What They Eat
Both animals filter small prey from the water, but they do it differently.
- Whale shark: a suction filter feeder. It draws in water and strains plankton, small crustaceans, and small schooling fish through its filtering pads. The Florida Museum puts the average at about 46 pounds (21 kg) of plankton a day.
- Blue whale: a lunge feeder that engulfs a huge mouthful of water and krill, then pushes the water out through its baleen. NOAA says the largest blue whales may eat up to 6 tons of krill a day. A 2021 study of tagged whales estimated up to 16 metric tons on a peak feeding day, though whales do not eat that much every day, and may go months without feeding during migration.
Habitat and Range
Whale sharks live in tropical and warm temperate seas, usually in surface waters of about 70 to 86°F (21 to 30°C). They are found in all such seas except the Mediterranean. They gather where food is plentiful, and they can dive deep, with one tagged shark recorded at 1,928 meters (6,325 feet).
Blue whales live in all oceans except the Arctic. They feed in cool, productive waters and move to warmer areas to breed. Eastern North Pacific blue whales, for example, feed off the US West Coast in summer and winter off Mexico and Central America. Their feeding dives are far shallower than a whale shark's deepest dives. Tagged blue whales feeding in Monterey Bay reached about 184 meters (600 feet) and stayed down up to 16.5 minutes.
Reproduction and Lifespan
Whale sharks are ovoviviparous. The eggs hatch inside the mother, and she gives birth to live pups about 2 feet long. One captured female carried more than 300 embryos, the largest litter documented. How long they live is not well known. Age estimates from growth rings in the vertebrae range from about 50 to over 100 years, and the Florida Museum says the true lifespan is unknown.
Blue whales give birth to one calf at a time, usually every 2 to 3 years. A newborn is about 23 feet long and weighs 5,000 to 6,000 pounds. NOAA estimates blue whales live around 80 to 90 years, based on ear-plug wax layers.
Are They Dangerous?
Neither animal is a threat to people. Whale sharks are filter feeders with tiny teeth that play no part in feeding, and the Florida Museum calls them generally harmless. It does note a few cases of whale sharks ramming sportfishing boats, possibly after being provoked. Blue whales are not known to attack people; see are blue whales dangerous.
You can swim with whale sharks in several places, including the Philippines and Mexico's Yucatán. Rules vary by site, but most ban touching or riding the sharks. In the Philippines, snorkelers must stay at least 4 feet away. Swimming with blue whales is not a normal tourist activity, and NOAA does not support swimming with wild whales.
Conservation Status
Both species are listed as Endangered by the IUCN.
- Whale shark: moved from Vulnerable to Endangered in 2016. The population is thought to have fallen by more than half over 75 years because of targeted fishing, accidental catch, and collisions with ships. Whale sharks are listed under Appendix II of CITES, which regulates international trade.
- Blue whale: a 2018 IUCN assessment estimated 5,000 to 15,000 mature individuals and 10,000 to 25,000 in total, compared with at least 140,000 mature whales in 1926. NOAA lists vessel strikes and fishing-gear entanglement as the main threats, with noise and climate change also a concern.