What is a Whale?

Whales, dolphins and porpoises are large mammals that live in water. They all belong to the same animal group, called cetaceans and are found in oceans, seas and big rivers around the world.

Whale or Fish?

Whales, dolphins and porpoises have flippers, fins and flukes for moving through water. Their bodies are similar in shape to some fish. However, there are many differences between whales and fish. Whales have smooth skin and no scales. Fish take oxygen from water, but whales must rise to the surface to breathe.

Different types of whale

Whales come in many different shapes, colours and sizes. Some are bigger than dinosaurs ever were, some are smaller than 1 metre (3 feet).

Two groups

There are seventy-eight different types of whales. Scientists sort them into two groups, called baleen whales and toothed whales. Baleen whales do not have teeth. They gulp their tiny food, and then water is pushed out through long flat bristles called baleen which hang down from the top gum. Baleen whales have two blowholes, side by side. The blue whale and other large whales are baleen whales. Toothed whales are smaller and include dolphins and porpoises. They use their teeth to catch fish and squid, but do not chew their food before swallowing it. Toothed whale have a single blowhole.

Dolphin or porpoises?

Dolphins and porpoises both have teeth, unlike some of the larger cetaceans. Dolphins and porpoises are also about the same shape, but look closer-there are many differences.

What’s the differences?

Dolphins are usually larger than porpoises. Most dolphins have a beak or snout, porpoises have a rounded head without a beak or snout. Dolphins have many cone-shaped teeth.  Porpoises teeth are quite different and are shaped like a spade. Dolphins are common, but porpoises are rarely seen. Most of our knowledge of porpoises comes from dead animals found in fishing nets. There are thirty-seven different types of dolphin, including those that live in rivers. There are only six different types of porpoises.

Smooth and sleek

Bumpy body parts would drag against the water, so whales have a streamlined shape with a neck that joins smoothly to the rest of the body. Their ears are no more than pinpricks filled with wax. Their reproductive organs and teats are tucked away in slits. Whale skin is silky smooth and without hair. Flippers and fins are flat, to cut through water.

A whale’s body

Whales are almost perfectly adapted to life underwater, apart from one thing – they have to come to the surface to breathe.


Whales have lungs and breathe air. The blowhole is actually a nostrils on top of the head. When a whale dives or swims under water, it holds its breath and strong muscles tightly seal the blowhole. Whales can hold their blood can carry more oxygen. Sperm whales can hold their breath for less than a minute. When the whale returns to the surface, the blowhole opens again and the old air is blown out. This makes the spout or blow. The whale then fills its lungs with new air.

Bones and muscles

Flippers have bones and are moved from the shoulder joint. The tail flukes, at the end of the whale’s body, do not have bones. They are supported by tough gristly tissue called ligaments. There are extremely powerful muscles in the lower part of the whale’s body. These move the horizontal tail flukes up and down to propel the whale along.

What’s inside?

The skeleton and internal organs of whale show that they evolved from land mammals.

Whale size

Whales can grow to such a huge size because their weight is supported by water. But being large has problems. If the whale is stranded on a beach, its ribs are not strong enough to protect the internal organs from being crushed by the weight of the body. Whales must eat enormous amounts of food. Some of this is stored in the thick layers of oily blubber which cover all parts of the body. Whales are warm-blooded, and blubber helps prevent body heat from escaping. The blubber of right whales, which live in cold waters near the North and South Poles, can be up to 70 centimeters (28 inches) thick.

Underwater senses

Whales and dolphins have the senses of sight, touch and hearing, just like we do. But we can only hear and see well in air. They can hear and see well both in air and in water.

Hearing and seeing

Sound is very important to whales and dolphins. To learn about their surroundings, some make clicking sounds which bounce off objects and return as echoes. By listening to the echoes, they can work out the size and shape of the objects and weather it is moving. The time the echo takes to come back tells them how far away an object is. All this is called echolocation. Toothed whales and dolphins use echolocation to navigate. Detect enemies and find food.

Happy Families

Whale pregnancies last between nine and eighteen months and usually result in a single birth. When giving birth, a mother is often helped and protected by other female whale known as ‘aunts’.

Water Babies

A baby whale is called a calf. At birth, the calf is up to one-third the length of its mother. It can survive in cold water and can swim. For its first breath, the mother or aunt nudges it gently to the surface to fill its lungs. The calf suckles underwater but near the surface, so it can breathe frequently. Fed on its mother’s super-rich milk, it grows rapidly. There is a very strong bond between mother and calf. Calves suckle for at least six months and stay close to their mothers for at least a year.

Living Together

There is both safety and sense in numbers. Groups make it harder for predators to attack. Groups give care and protection to the young. Hunting can also be easier in a group.

Working together

A group of whales is called a pod. Toothed whales from the largest groups. Ocean-living dolphins often combine several pods into a huge herd of more than 1,000. These herds are very good at searching over vast areas for scattered schools of prey. Most pods are centred around adult females. For example, sperm whales form ‘ nursery schools’ of females and calves. There can also be a sad side to being part of a group. Whales that live together sometimes die together when they follow each other to strand on beaches.

Baleen whales

A baleen whale eats tiny sea creatures, so it must catch enormous quantities if it is to have a decent meal.

Skimmers and gulpers

Baleen whales catch food by straining water through the thick, comb-like baleen that hangs like a moustache from its top gum. This is called filter-feeding. Baleen whales are divided into two groups, according to just how they do this. Rorquals or ‘gulpers’ swim quickly after schools of prey, gulping in massive mouthfuls of water and food. Then the whale closes its mouth and uses its tongue to push the water out through the baleen are swallowed. Right whales feed by skimming food from the water. A right whale swims slowly at or near the surface with its mouth slightly open so water gushes through. Prey is collected on baleen plates at the sides as water flow out.

The Blue whale

The blue whale is the largest animal that has ever lived on earth. It is a baleen whale. It lives in the open ocean and is not often seen near the coast.

Ocean Giant

The blue whale can grow to 28 meters (92 feet) long, which means it would stretch from one end of a basketball court to the other. It can weigh more than 170 tonnes – that’s about 30 elephants. The blue whale is the noisiest animal on earth. Its call is louder than a jet engine, and can be heard from hundreds of kilometers away. Humans are the whale’s only predator. Whalers killed so many that the animal almost became extinct.

Toothed Whale

Toothed whales are generally fast swimmers. They chase, catch and swallow prey. Both dolphins and killer whales belong to this group.

Food and feeding

Toothed whales often use echolocation to find their food, which is usually large fish and squid. Some toothed whales, such as the sperm whale, dive into deep, dark waters to find and catch prey. Other toothed whales, such as the bottlenose dolphin, hunt in groups near the surface. Killer whales are the only whales to eat warm-blooded prey. They are also the only whales to rip chunks from their prey swallowing.

The amazing sperm whale

Sperm whales are found in most of the world’s ocean from the tropics to the edge of the Polar Regions. They dive deeper than any other whale.

Giant the deep

The sperm whale plunges up to 3,000 metres (10,000 feet) into pitch black waters to hunt for its favourite food, the giant squid. It can stay underwater for more than two hours. Sperm whales are named for the wax-like oil, called spermaceti, found in an organ in the front of the whale’s huge square head. A 30 tonne whale may have up to 2.5 tonnes of spermaceti oil in its head.

Amazing Facts

  • The sperm whale is the largest of the toothed whales, growing to 20 metres (64 feet) long.
  • The sperm whale has the biggest brain of any living animal.
  • Sperm whales can live to seventy years and more just like humans.