Do you know what blue whale eat. Well blue whale's favorite food is krill. If you wondering why the biggest animal in the world eats the smallest animal it's because blue whales have no teeth. If you are wondering how it eats the krill the eat it by pushing the krill. with its tongue. Did you know that blue whales eat 40 million krill a day. Thats crazy. Blue whales are gargantuan. That means there massive which means there esophagus is inches wide. As you can see they eat small things.