How do blue whales protect them selves from enemies?

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

Humans are the biggest threat to blue whales. Nearly 90% of the world population of these animals were wiped out over the past century by humans by whaling.