Blue whales are the largest animals on Earth. They weigh as much as twenty elephants! But they eat very small animals called krill.
Krill live in the ocean. They are two inches long. They look like shrimp The krill eat plankton that floats in the ocean. The plankton uses the sun’s energy to make food.
Blue whales do not have teeth. Instead, they have bristles called baleen in their mouths. When whales eat, they gulp large mouthfuls of water and krill. The whales squeeze the water back out with their tongues, and the krill is trapped by the baleen. Then the whales swallow the krill. Yum!
The krill eat the plankton. Then the blue whales eat the krill. This is called a food chain. A food chain shows the animals that eat each other.
The Southern Ocean is just right for the plankton, the krill, and the blue whales. It has cold water, nutrients, and lots of sunlight in the summer.
There aren’t many blue whales in the Southern Ocean today. Now there are laws protecting the blue whales, but their numbers are still low.

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