The main food source of blue whales is krill, and krill mainly feeds on plankton smaller than itself and feces of other large animals. Although blue whales eat dozens of tons of food every day, they naturally eat more, and these large amounts of feces discharged by blue whales will become nutrients for krill.

About hundreds of thousands of years ago, the earth entered the ice age, and many areas of the earth were covered by glaciers. The melting of glaciers can bring nutrients such as iron into the ocean, which will gradually lead to the rise of sea level, thus making many organic substances appear on the sea surface.

This environment makes krill and a large number of plankton grow and breed wildly, and these krill and plankton are the delicious food that whales dream of. At this time, various superior conditions have evolved, and the food in the marine environment is inexhaustible. The transformation of the blue whale's body shape finally ushered in a major turning point and began to become enormous.

And as the body gets bigger and bigger, whales begin to become invincible, because big is a symbol of strength. Although the blue whale has no attack power, its huge body is enough to make it not afraid of any other predators in the ocean. Until now, blue whales have basically no natural enemies except humans.

Therefore, through this cycle, a closed food chain has been formed between blue whales and krill. It can be said that the blue whale has achieved food self-sufficiency to a certain extent and contributed to solving the food shortage. In the end, the blue whale became the largest animal that ever lived on the earth.