The world of whales, dolphins and porpoises is an astonishing one. A family consisting of mammals, like us, who breathe air, nurse their young and have warm blood, live in the forbidding ocean, perfectly evolved to life in the sea.

Another fascinating factor in the world of cetaceans is the variety. They range from the blue whale, the largest animal ever on Earth, to the tiny little Vaquita porpoise. The orca, of course, is a stark contrast of black and white; the Indo-Pacific Hump-Backed Dolphin is a brilliant pink; the Grey Whale is a mottled grey, and the Atlantic White-Sided Dolphin is grey, black and white with a bright orange streak. The Sperm Whale's head is a block-like rectangle, the Fin Whale is a stream-lined giant, and the Northern Right Whale Dolphin looks like a torpedo. Some have dorsal (back) fins, some don't. Some jump, some won't. Some live in families, others live alone.

There are common factors each member of the family Cetacea share. All have pectoral flippers to steer and blowholes at the top of their head to breathe. Scientists assume that during their return to the sea, at some point the whales' nostrils moved back to the top of their head to make it easier to breathe quickly. They all have tails to propel themselves, they all give birth to live young and nurse them, and they all live their entire lives in the sea.

Collectively, this group of strange and fascinating creatures is called the family Cetacea. The animals themselves are called Cetaceans. To make this page simpler, I usually refer to them as a group as simply cetaceans, or just whales. The difference between whales, dolphins and porpoises is purely superficial, if it's there at all. Some people contend that they are just all "whales". Basically the difference between a dolphin and a whale is the size, like boat and ship, or mound and hill. A porpoise is even smaller. But that doesn't work, because some dolphins are smaller than some porpoises, and some whales are smaller than some dolphins. And sometimes, we don't even know if something is a whale, a dolphin, or something else entirely. There might very well be whales, dolphins, porpoises and a special group of "grampus", including pilot whales and orcas, who have long confused people.

As every third-grader knows, cetaceans are divided into two scientific families: toothed and baleine.

Toothed: Toothed whales (including all the so-called dolphins and porpoises) have, you guessed it, teeth. Ranging from the mysterious beaked whales, who have 1 or even no teeth, to the orca, who can have 50 cone-shaped teeth, the variety is much greater in toothed whales than baleines. They eat fish, squid, or other animals, typically live in close-knit or large groups, and are invariably more social than baleine whales. They also seem to have higher intelligence, though measuring intelligence is difficult.
There are a number of different groups in the toothed category:

Sperm Whales
The intriguing sperm whales are named that because they have a valuable, oily substance in their heads called spermaceti, so named because early whalers thought it was sperm. We now know its not, and it may actually have something to do with why sperm whales can dive so deeply.
There are actually 3 species in the sperm whale group: the Sperm Whale, the Dwarf Sperm Whale, and the Pygmy Sperm Whale. The former two hardly ressemble the whale they're named after, but are so-called because they, too, have spermaceti.

Beaked Whales
Beaked Whales are fascinating and elusive. They are very rarely seen at sea, and despite the fact that there are over 19 species of them, only a few (mostly Cuvier's, Baird's, Northern Bottlenose, and Blainville's) can be seen relatively regularly. Most of what we know of this family comes from dead specimens washed up on the beach. There are a few studies in place for living whales: a Northern Bottlenose Whale study is happening in Nova Scotia, and Cuvier's Beaked Whale is fairly well known. At the other end of the scale, however, is Shepherd's Beaked Whale, or the mysterious Spade-Toothed Whale, which has never been seen alive and is only known from a few bones.
These whales are unusual in that mostly they have only 1 or 2 teeth, and often, these teeth wrap around the jaw, making it impossible to open more than a few centimetres. Scientists think they probably feed on squid, by sucking them in. The whales are also very deep divers, perhaps contending with the Sperm Whale for deepest diver.

Narwhals & Belugas
Narwhals and Belugas are unusual in their own sense. They really don't belong to any family, instead standing in a group of their own. Narwhals, of course, are known for the amazingly overgrown tooth (the "tusk") males grow. They live in fairly stable groups in the Arctic, and are also recognizable by their mottled colouring. Belugas are equally distinguishable by their bright white colouring and their unique necks: they are the only cetaceans who can move their necks. They live in huge groups, also in the Arctic.

River Dolphins
River Dolphins are another interesting family. Unusually, they live in (you guessed it!) mostly rivers. There are 4 species (the Baiji, the Boto, the Fransiscana and the Indus/Ganges River Dolphin), and they are odd-looking, usually blind, and many of them are on the verge of extinction. Indeed, the Baiji, the Chinese river dolphin, may be the first cetacean to go extinct in written history (there are only about 13 left, if that). Little known, these dolphins are nonetheless usually right in the center of human activity. Future research on these mysterious, endangered creatures will surely yield fascinating results.

Oceanic Dolphins
And now we come to the group that is full of the most common and familiar dolphins out there. The famous Bottlenose species are a member of this group, as are most other dolphins known to man-kind. From the strange finless Rightwhale Dolphin to the playful Dusky, there is a wide variety in behaviour, appearance and diet among the 29 species found in this grouping.

Blackfish
For lack of a better name, this group includes 6 species, all of which are technically dolphins. Scientifically, this isn't an actual separate group. However, evidence that these animals merit a separate classification may prove very popular. All of the animals have small or no beaks, are quite stocky and fairly large, and they are all relatively black. They are also all very social, usually occuring in large, close-knit groups.

Porpoises
While there isn't really a scientific basis for the difference between dolphins and porpoises, there are 6 species that officially bear the name porpoise. Smaller than most dolphins, they have no beaks and often slip by unnoticed. They usually are found in small groups and do not engage in the spectacular theatrics other cetaceans do.

Baleen: Baleen whales are unique in the fact that they have no teeth. And they're huge. In place of teeth, they have hair-like plates of baleen, which acts as a filter for their tiny food. The baleen whales are home to the two biggest animals on the planet.