There are more than 70 species, or kinds, of whales, dolphins and porpoises. They are the family called cetaceans (say: see-tay-shuns). Cetaceans are warm-blooded, air breathing mammals that can be found in all the world's oceans and even in inland rivers.  

Some whales are baleen whales and some are toothed whales.  Almost 90% of cetaceans are toothed whales. They are generally smaller than baleen whales, and have one blowhole. Males are generally larger than females. 

Baleen whales

Baleen whales have plates of baleen growing down from the upper jaw, in rows down each side of the mouth. Baleen is made of keratin, which is what human hair and fingernails are made of.  Baleen grows continuously because the lower part wears off. The stiff outer edge is smooth and the inner edge is frayed, forming a mat which acts as a strainer during feeding. When feeding, baleen whales swim with their mouths open, taking in vast mouthfuls of water.  Grooves on the outside of the throat expand, increasing the mouthful. Tiny creatures called plankton and krill are sucked in through a gap in the front baleen. The whale closes its jaws, the grooves on the outside of the throat squeeze together, forcing the water out through the baleen at the sides of the mouth, leaving the food inside on the baleen. 

Baleen whales are some of the largest animals ever. This size protects them from predators and makes it easier to keep body heat. Some baleen whales have huge heads about 1/4 or 1/3 of their body length.  Living in water, they do not have to support their huge weight, as an animal on land does.

Baleen whales in the northern hemisphere are usually slightly smaller than those found in the southern hemisphere. All have a similar torpedo-shaped body for efficient swimming. Most are black or grey. Some are darker on top than underneath, which is good camouflage. Some species, such as Grey (also spelt Gray) and Sei whales, have white or faintly colored markings. There are 10 species, or kinds, of baleen whale. Some of them are the: blue, finback, right, sei, and humpback  whales.

Toothed whales

Toothed whales have peglike teeth. The number and size of the teeth depend on the species. The teeth are designed for gripping food rather than chewing it. They swallow their food whole or in very large pieces. Most toothed whales eat fish, but some also eat invertebrates, such as crabs or squid.  Orca whales, also called killer whales, are the most effective predators in the ocean, eating fish, seabirds, and marine mammals such as seals or other whales. 

Most toothed whales are dolphins and porpoises, but there are a few large toothed whales such as orca, or killer whale, and the sperm whale.  Toothed whales are believed to be among the most intelligent animals on earth. The intelligence of dolphins, Beluga and killer whales has been shown in captivity, and sperm whales have the largest brain of any animal.

The largest toothed whale is the sperm whale, about 18 m long. It is thought to dive deeper than any other cetacean. The pygmy sperm whale and dwarf sperm whales are much smaller, though similar in appearance.

One of the smallest toothed whales is Hector's dolphin, about 1.3 m. There are 66 species, or kinds, of toothed whale, grouped in several families. Some toothed whales are: bottlenose, orca, pilot, narwhal, and Beluga whales, and dolphins and porpoises.

One family of toothed whales is known as beaked, or sword-nosed, whales. They are the least known of all cetaceans, living in deep water far from land and rarely seen. Some species have never been seen alive but have been studied only when dead ones are washed ashore. It is believed that there are 20 living species of beaked whales, including the North Pacific bottlenose whale, Shepherd's beaked whale, Sowerby's beaked whale, and Stejneger's beaked whale. 

Another family of toothed whale has only two species: the narwhal and Beluga whale. Neither has a dorsal fin. They have blunt- shaped heads, are grey colored at birth, and whiten as they mature.  Adult Beluga whales are a brilliant white, while narwhals have white bellies and mottled greyish backs and sides. Belugas have 8-10 teeth in each jaw. Narwhal have only two teeth in the upper jaw, one of which develops into a spiral tusk in most males and some females.

Body and behaviours

Whales are warm-blooded. They have thick layers of fatty blubber under the skin to help keep them warm in icy waters. Being mammals, they must surface to breathe air. However, they can hold their breath for a long time, some of them for several hours, while they dive to the deepest parts of the ocean. When they surface to breathe, a spout of water and steam escapes from a blowhole on their heads.

Baleen whales have two blowholes, while toothed whales have one. Blowholes are covered by muscle flaps to provide a water-tight seal that prevents water from entering the blowholes. Each blowhole leads to an air passage leading to the whale's throat and lungs. When they surface, whales breathe out and the burst of air and water, called a spout, can be seen about 2 kms away. The breath bursts out at up to 400 km per hour and can go as high as 5 metres. Each species has a different shaped spout.

Whales locate objects by bouncing high-pitched sounds off them and 'reading' the echoes. This is called 'echo-location'. Whales live in groups called pods, and members communicate with each other using a wide range of sounds such as squeaks, clicks and whistles.

Whales can swim at great speed. Orca, or killer, whales can reach 60 kph, some dolphins 30 kph, the large fin whales cruise at 22 to 26 kph. Right whales and grey whales are a bit slower, with a top speed of about 11 kph.  

When a whale leaps up out of the sea, it is called breaching. Sometimes its whole body clears the water completely, and then it falls on its back with a tremendous splash. This is thought to communicate its position to other whales. The splash can be heard for kilometres. If the whale falls forward instead of backward, it is called a head lunge. Sometimes whales have their heads out of the water for a while. This is thought to be so they can see the coastline to check where they are. This is called 'spy hop'. Whales sometimes lift their tails (each half is called a fluke) high above the water and slap them down on the surface making a tremendous splash that can be heard far away. This lets other whales know its position. Tail slapping is often aggressive behaviour. Sometimes whales slash their flukes from side to side on the surface to create turbulence.

Sometimes whales get onto a beach and cannot get back into the water. This is called stranding.  It is not known why they do this. Sometimes people can get them back into the water and they swim away, but sometimes they turn around and beach themselves again.  

On land they can die because the weight of their bodies is too great and their organs get crushed.

Life Cycle

Most baleen whales spend the summer feeding continuously before migrating to give birth in warmer waters. Whales that feed in the Antarctic travel north, and those that feed in the Arctic travel south, to warmer waters for breeding. They eat little both on the journey and while they are in warm water. Blubber (a layer of fat about 30 cm thick) gained during the feeding season gives them nourishment.  

The length of time a female whale is pregnant depends on its species. A dolphin is pregnant for about 10 months, and larger whales for up to 16 months. The calf is born tail first, and as soon as the head appears, the calf is nudged to the surface to breathe. Calves of baleen whales are born with small soft baleen plates. Whale calves stay close to their mothers. The calf's movement is helped by the current created by its mother's swimming. Whale mothers protect their young fiercely.  Calves suckle underwater, drinking milk from teats hidden inside a slit in their mother's belly. Whale milk has a high fat content so calves grow fast and develop blubber quickly, ready for the cold waters when the whales return to the Antarctic or Arctic.

Pectoral (front) fins are frequently used to stroke the body of another whale, probably during courtship and mating. Mothers and calves also stroke one another frequently. Baleen whales have one mate only, and live in family groups. Toothed whales live in larger groups, called pods, often with one male and a number of females and calves.

Conservation status

Most whale species are endangered and are protected. Whaling was a major industry in the past, dating back to the 12th century, for meat and many products that were made from oil, bone and other parts. By the 18th Century whales were seriously threatened and the development of fast steam-powered whaling ships in the 19th Century brought whales close to extinction. In the 20th Century, large factory ships were built. The whaling ships could then bring dead whales to a ship to be processed instead of having to travel back to land. This meant even more whales were killed. Today the numbers and species of whales that a country can kill are strictly limited by international agreement, and most countries have banned whaling completely.

Sperm whales were once hunted for the large amount of oil that could be obtained from their blubber and from a part of their head called the spermaceti organ. In the intestines of sperm whales a waxy substance forms around the beaks of squid they have swallowed. This is called ambergris, and was used to make perfume. Huge numbers of sperm whales were killed between the 17th and 20th Centuries, and they are still classified as endangered. Products from whales can now all be manufactured or obtained elsewhere, so there is no longer any need to hunt whales. 

Dolphins and other whales are often caught in the nets of commercial fishing boats and drown because they can't reach the surface to breathe. They are affected by pollution of the oceans and by shipping.

It is always a good idea to use more than one source of information, so here are some others for you to investigate.

Read about whale migrations and about the species seen in Australian waters:

• http://www.environment.gov.au/marine/marine-species/cetaceans/species-found-australian-waters

• http://www.whale-world.com/facts-about-whales-for-kids/

Read about the blue whale, the largest mammal ever:

https://www.natgeokids.com/au/discover/animals/sea-life/10-blue-whale-facts/