What eats blue whales?

Answer 1

Younger and small blue whale calves may be attacked by "killer whales" (Orcas) or by other large sharks.

Other than humans, the "cookiecutter sharks" (Isistius brasiliensis) also "eat" whales, taking bites from large whales such as the blue whale. These sharks do not normally attain a size over 3 feet (1 m), and their small bites would not normally cause any real injury to a healthy whale.
Adult blue whales have no natural predators. They are too big and too strong to be attacked and killed by any animal. However, Orca's (Killer Whales) are known to attack and kill youngsters. A group of Orca's can easily hunt a baby blue whale if its mother is not around. Otherwise, they have no natural predators
sharks

Answer 2

The blue whale is thought to feed almost exclusively on small, shrimp-like creatures called euphausiids or krill. During the summer feeding season the blue whale gorges itself, consuming an astounding 4 tons (3.6 metric tons) or more each day.

Answer 3

Adult blue whales have no natural predators. They are too big and too strong to be attacked and killed by any animal. However, Orca's (Killer Whales) are known to attack and kill youngsters. A group of Orca's can easily hunt a baby blue whale if its mother is not around. Otherwise, they have no natural predators