The heart of a blue whale is as large...

What is the biggest animal on Earth? Hint: It’s not an animal that lives on land. It’s the blue whale. Blue whales can grow to be 80 feet (24 meters) long and weigh 150 metric tons. The heart of a blue whale is as large as a small car!

WHALES ARE NOT FISH

The body of a blue whale looks a lot like the body of a fish. All whales look like fish, but whales are not fish. Whales are mammals that live in water.

There are many differences between fish and whales. Whales are much bigger than fish. Fish stay underwater all the time and breathe through gills that take oxygen out of water. Whales breathe through lungs just as you do, so they must come up for air. Fish are cold-blooded, which means their body is the same temperature as the water around them. Whales are warm-blooded (like humans), and so their bodies always stay warm. Fish lay eggs. Whales, like almost all mammals, give birth to live young and feed their babies on mother’s milk.

Fish and whales both have tail fins. The tail fins of a fish are vertical (up and down). A fish swims by moving its tail from side to side. The tail fins, or flukes, of a whale are horizontal(side to side). A whale swims by waving its tail up and down. Whales also have two front limbs called flippers that they use to steer.

DIFFERENT KINDS OF WHALES

There are more than 75 species (major kinds) of whales. Zoologists (scientists who study animals) divide whales into two groups by the way they eat. One group, the toothed whales, have sharp, pointy teeth for catching fish, squid, and other prey. Sperm whales, beaked whales, narwhals, belugas, dolphins, and porpoises are toothed whales.

The other group, the baleen whales, do not have teeth. Instead, they have big plates with brushes on the edge called baleen, or whalebone. Baleen whales take in a big mouthful of water. The baleen then traps small fish and plankton (tiny plants and animals that float in the ocean). Rorquals, gray whales, blue whales, and right whales are some of the baleen whales.

BLUBBER AND BLOWHOLES

A whale has smooth skin that can be black, white, or other colors. Under their skin, whales have a thick layer of fat, called blubber. Blubber stores energy and helps keep the whale warm in cold water.

Whales don’t have noses. They breathe in and out through blowholes on the top of their heads. Toothed whales have one blowhole. Baleen whales have two blowholes. Whales can hold their breath underwater for a long time. Baleen whales can stay underwater about an hour. The sperm whale can stay underwater for even longer—about 80 minutes.

When a whale comes to the surface, it blows air out through its blowhole. The warm air looks like a mist. The mist is called the spout.

SEEING AND HEARING UNDERWATER

Whales have excellent eyesight. Oily tears help keep their eyes safe and clear underwater.

Whales have good hearing. Toothed whales use sound to hunt for food in the deep, dark ocean. They send out a sound that bounces back when it hits a fish or other animal. The echo tells the whale where the animal is.

Baleen whales do not have a good sense of smell. Toothed whales can’t smell at all.

COMING OUT OF THE WATER

Whales never climb up on land. But some whales can jump right out of the water. They land on their backs with a loud smack. Scientists call this behavior breaching. Scientists don’t know why whales breach. Are they trying to attract a mate? Are they “talking” to other whales far away? Or do they just want to get a good look at what is around them?

MIGRATING WHALES

Some whales migrate (move from place to place). These whales swim great distances every year. Baleen whales travel to cool waters near the Arctic or Antarctica every summer. They feed on krill, small animals that look like shrimp. In the winter, baleen whales head for warmer waters near the equator to breed.

Other whales do not migrate. Narwhals, for instance, live year-round in the cool waters of the Arctic and North Atlantic oceans.

HAVING BABY WHALES

After male and female whales mate, it takes from 10 to 16 months for a baby whale to form. The length of time depends on the whale species. A whale gives birth to only one baby at a time. The baby whale nurses on the mother’s milk for as long as a year.

Some whales can mate and have babies at 7 years of age. Other whales take longer to mature, and first mate as late as age 14.

LIFESPAN OF A WHALE

Small whales live about 20 years. Large whales can live to be 60 years old.

ANIMALS THAT HUNT WHALES

Some large sharks, such as the great white, can eat whales. But people are the main whale hunters. People began to hunt large numbers of whales in the 1700s. They hunted the sperm whale for a waxy liquid used to make candles and for whale oil to burn in lamps. People hunted baleen whales for whalebone to make combs and other products.

People no longer hunt whales for lamp oil or whalebone. However, they still hunt whales for oils and other materials used to make soap and cosmetics. Many whales, including right, bowhead, gray, and blue whales, have become endangered. Some countries in the mid-1900s decided to limit or forbid whale hunting. A few nations kept on hunting whales. Conservation groups now ask that all whale hunting be stopped. They fear that some kinds of whales could disappear forever.