Blue Whale: Facts & Habitats

Instructor: Lauren Posey

Lauren has taught intermediate reading in an English Language Institute, and she has her Master's degree in Linguistics.

In this lesson, we're going to look at the largest animal in the world: the blue whale. You'll learn about its habitat, as well as some interesting facts about its life and behavior.

The World's Largest Animal

What do you think is the largest animal to ever live on Earth? You might be inclined to say a dinosaur, or some other extinct animal. The truth is, the largest animal ever (as far as we know) is still alive today! It is the blue whale (Balaenoptera musculus). Adult blue whales can be 82-105 feet long, and they weigh about 200 tons (400,000 pounds). That's longer than two school buses, and heavier than 33 elephants put together! Can you believe that their heart could weigh the same as an automobile? These whales are also known for a lengthy life. On average, blue whales live for 80-90 years.

Blue whales are the largest known animal to have ever lived
Blue whale

Interesting Facts

Blue whales are fascinating and unique creatures. They get their name because they look pure blue in the water. In reality, they are a grayish blue, and their stomach can be almost yellow. In addition, they are extremely loud. They make a variety of calls, and scientists think they can communicate with other whales that are 1,000 miles away! Blue whales seem to travel alone or in very small groups, but it is possible that their loudness makes it so they can travel together while seeming, to us, to be very far apart. That is, a group of blue whales may be traveling together and yet still be miles away from each other.

Blue whales also use sound for echolocation. This is when they call out, and their sound bounces off of surrounding objects and sends a picture back to the whale. It is a very useful tool for moving around when there is little or no light, which is the case for much of the deeper ocean.


Given how large blue whales are, you would think that their food would have to be large, too. Actually, this is not true. Blue whales live entirely off of krill, one of the smallest creatures in the ocean. They eat four tons of these small, shrimp-like animals every day, which adds up to about 40 million krill every single day.

Blue whales eat using baleen, which are hairy, hard plates that take the place of regular teeth. The whale opens its mouth and sucks in a huge amount of water and krill together. Then it pushes the water back out, but the krill are left behind, trapped by the baleen.

This drawing shows some of the baleen in the mouth of the whale
Blue whale drawing

Baby Blues

Even as babies, blue whales are enormous. At birth, they weigh almost 6,000 pounds, and are 25 feet long. Since they are mammals, they are born alive (not from eggs), and they start their lives by drinking milk. They drink milk until they are seven or eight months old. By this point they are up to 45 feet long and can manage to migrate (move to a different area) on their own. They can breed after they are 5-10 years old.


Blue whales are endangered because of whale hunting. It is illegal now, but they were hunted commercially for their oil and meat for many years. Over that time their population dropped by 70%-90%. It is a long process to recover from that big a loss, and blue whale numbers are nowhere near stable yet.

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