Whales are carnivores, not herbivores. Herbivores have strictly plant-based diets, while carnivores consume meat. A whale's typical diet includes octopus, fish, shrimp, krill and squid, making these mammals carnivores. A blue whale can consume 4 tons of krill daily.
While whales do not eat the same types of meats that humans or land animals eat, they are still considered carnivores. If even the smallest percentage of an animal's diet is meat-based, that animal is a carnivore. Carnivores are sometimes called predators because they hunt their food prior to consuming it. Whales are carnivores that eat herbivores; much of their sustenance comes from fish that have a plant-based diet.