Cetaceans are an order of marine mammals most commonly called whales. There are 77 species, which are divided into two main groups; baleen whales and toothed whales. Baleen whales gather their food by filtering out fish and tiny plankton from the water with the aid of comb-like plates that hang from the roof of their mouth. In other words, they do not have teeth! This group of whales represents the largest animals to have ever lived on earth and you have probably heard of some of them. The most popular species of baleen whales are the blue whale, the humpback whale and the gray whale. The other group, the toothed whales, includes the dolphin and the porpoise. They, of course, have teeth and use them to catch and hold their prey. The teeth are not used for chewing their fish, instead they swallow everything whole. Some toothed whales may have as many as 260 teeth, while the narwhal (sometimes called the unicorn whale) has only one.
There are about 65 species of toothed whales. They range in length from the 1 m (3 foot) harbor porpoise to the 19 m (62 foot) sperm whale. Their colour may vary from black to white, but most species are shades of gray with a lighter underside. This is called "countershading" and helps the whales become less noticeable to predators around them.
We have mentioned how the streamlined body helps them maneuver in the water. Their powerful fluke propels them to an estimated 55 km/h (35 mph). Notice that the fluke moves in an up and down motion as compared to the fish whose fins move from side to side. The pectoral flippers are used for steering and contain five bones very similar to the human hand. On their back is the dorsal fin which helps stabilize the animal in the water when it turns. Neither the dorsal fin nor the tail fluke has bones, instead they are made of cartilage like that of our ears and nose.
Whales are able to make long, deep dives under the sea. This is possible because of several unique physiological adaptations, including the phenomenon known as bradycardia, which simply means the slowing down of the heart upon diving. Second, their blood carries more oxygen than other animals. And third, during the dives, blood is shunted away from most of the body and only goes to the vital organs (the heart, lungs and the brain).
In almost every animal, breathing is involuntary (automatic). This means that most animals do not have to think about breathing. With the whales, however, their breathing is voluntary, meaning that they have to think when to breathe. In this way, the whale breathes only when it is sure the blowhole is out of the water. Being air-breathing mammals, whales could drown if they could not return to the surface or if they took water into the blowhole and lungs. Because of this, whales are not able to sleep for long periods of time like most animals. Instead, they take short "cat naps" and then return to the surface to breathe.
Probably the most fascinating characteristic of the Cetaceans is their ability to explore their surroundings by using sound, called echolocation. Sounds produced in air sacs under the blowhole are sent out, bounce off objects and then return to the animal. The sound is a high-pitched, rapid click-click-click. By noting the time it takes to return, the animal can tell how far away the object is, what the shape is, in what direction it's going, and of what it is made.
Scientists have done research on echolocation by placing rubber cups over the eyes of dolphins and then sending them through an underwater maze. The dolphins negotiated the maze perfectly each time! This "seeing with sound" is truly a remarkable sense, and one that is sometimes hard for humans to imagine.
Sound travels faster and further in water than it does in air. As a result, when a whale communicates, its sounds can sometimes be heard for hundreds of miles. These sounds are produced by the blowhole or in a series of nasal sacs that are located just below the blowhole. The sounds are produced by forcing air out through the blowhole or from one nasal sac to another, much like letting air out of a balloon.
Whales are considered to be the smartest animals in the ocean. People are always amazed at their ability and eagerness to learn. However, in the past, their intelligence has been somewhat exaggerated. Today, most scientists feel that whales are about as smart as chimpanzees.
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