Together with dolphins and porpoises, whales belong to the order Cetacea. You can call them cetaceans if you want, and describe them as cetaceous. They won't mind. The word cetacean is from the Latin cetus (a large sea animal), and the Greek word ketos (sea monster) - so it's a pretty cool name ("large sea animal monster") if you ask me.

If you ever see a cetacean in an aquarium you will be able to easily identify it as such by a plaque or sign near its pool, but how to tell cetaceans from fish in the wild? It's easy actually. First, fish have gills so they can get oxygen from water, while whales and other cetaceans breathe air through a blowhole (or two) on the top of their head instead. Blowholes are kind of like oddly placed nostrils. Typically, toothed whales (aka Odontocetes) have one blowhole, and baleen whales (aka Mysticetes, aka the "moustached whales") have two.

Second, whale tails are horizontal. Same with dolphins and porpoises. Fish have vertical tails. Whales have powerful muscles in the rear third of their body to move their tails up and down, which propels them through the water. Fish, on the other hand, swim by moving their heads from side to side, creating a sort of wave down their bodies that moves their tail back and forth. Next time you go for a swim, give both methods a try. But before going into deep water you should already know how to swim like a person because you will find it very hard to swim like a fish or a whale.

So what are these baleen whales with the two blowholes that I mentioned? Well, they have baleen plates instead of teeth. Baleen plates are comb like things growing down from where other whales would have teeth. Sort of like a moustache on the inside of their mouth (so a mouthstash maybe?). Baleen, also called whalebone, is made from the same sort of thing that makes up our hair and fingernails. It's called keratin, and is springy and flexible. Before plastic, people used it to make all sorts of things. Things like hairbrushes, chair springs, skirt hoops and umbrellas. Yep, whale umbrellas - I kid you not!

To feed, baleen whales take in a huge amount of water. Some species even have deep grooves on their throats that expand when they take in water. Then the whale squeezes the water back out through its baleen. The baleen plates act like a sieve - filtering out the krill (like tiny shrimp), small fish and other tiny critters the whales eat. So, amazingly enough, the largest animals on the planet survive by eating lots of little things. Just think about that the next time you get served brussels sprouts, baby corn or those miniature cocktail sandwiches.

There are major gaps in our knowledge about the reproductive rates of many whale species, but it is known they reproduce relatively slowly compared to most fish species. Minke whales are thought to give birth to one calf every year or two, humpbacks have one every two to four years and fin whales one every two to five. By contrast, some fish produce millions of eggs every spawning season, and even with much higher reproductive rates many fish stocks currently suffer from over exploitation.
And commercial whaling is not the only threat to the whales these days. They also have global warming, pollution, over fishing, ozone depletion, noise such as sonar weaponry, entanglement in fishing gear and ship strikes to deal with. It's no wonder there are so few healthy whale populations left around the planet.

More information:

About whale conservation »
Whale info from the International Whaling Commission »
For students and teachers »
How whales work »
Become an Ocean Defender »