On a scale of one to ten, seeing dolphins when you are in a canoe truly ranks as an eleven. First you might see a fast-moving dorsal fin— so you think, "Shark!" Then: the sound of a noisy exhalation at the surface, with a shower of spray. Your pulse quickens— you are not alone! Two dolphins swiftly pass beneath your canoe; will they come up beneath you and upset your boat? What they are doing, saying hello? Playing? Hunting? Only with dolphins do you feel that they are probably as curious about you as you are about them. If you fall out of your canoe and are attacked by a shark, they may even save your life. Truly, of all the creatures in the ocean, they are our best wildlife friends. Not that we always treat them as such.

So who are they?
Let's clear up a common mistake right at the beginning: these sleek beings swirling around our canoes are very likely bottlenose dolphins, scientifically named Tursiops truncatus. In Florida waters they are often incorrectly called porpoises. As there's a colorful, well-known fish also called dolphin (right), people began to call T. truncatus a porpoise so that nobody would think they were eating "Flipper," the beloved bottlenose dolphin television and movie star. But the bottlenose dolphin is not a fish; it is an air-breathing mammal like us. They bear live young and feed them the milk they produce. In the U.S.A. up until the early 20th century, bottlenose dolphin was on the menu. Once people got to know them better, it became a taboo to eat the meat of our wildlife friend. Yet in some countries, people still do hunt them for meat.

The cosmopolitan dolphin
Bottlenose dolphins are found in oceans all over the world, from Norway to Australia. In colder climates and deeper oceans, they are larger so as to maintain their core body temperature. They also may have diverse color patterns and markings, varying enough so that it was believed they belonged to different subspecies. The ones we would usually see while canoeing along Florida's coasts tend to be smaller and lighter gray than the oceanic and northern bottlenose dolphins. All dolphins exhibit countershading, meaning that they are darker on their dorsal, or upper sides, and lighter in color on their ventral, or underneath side. Many creatures are colored in this manner, to help them blend in with their environment depending on which side they are seen.

Dolphins? Porpoises? Who's who?
Dolphins have been placed by scientists into the Family Delphinidae, and porpoises into the Family Phocoenidae. Dolphins have a snout or beak, properly called a rostrum, bearing that well-known grin, unlike the true porpoises, that never have a rostrum. To confuse the matter, though, some types of true dolphins lack a rostrum. Dolphins and porpoises are all cetaceans, or odontocetes, which means "toothed whales" but dolphins have conical teeth and porpoises have shovel-shaped teeth, sort of like human incisors. Porpoises are smaller than dolphins, and have blockier bodies while dolphins are about the most streamlined animal we know. Dolphins have a crescent shaped (falcate) dorsal fin, but porpoises have a more triangular one, and a porpoise from southeast Asia lacks a dorsal fin entirely (above). Dolphins are known to live to be fifty years of age (although most don't), but most porpoises will not live to their twenties. Bottlenose dolphins begin breeding later in life than porpoises, and also keep their calves with them longer and breed less frequently. Porpoises in general are much more reclusive and shy, and except for the most exuberant one, the Dall's porpoise (Phocoenoides dalli), don't joyride the pressure wave of boats as bottlenose dolphins are frequently seen to do. Porpoises, though less studied than the bottlenose dolphin, seem to be more solitary, while dolphins develop strong bonds with their relatives and with humans, and are far more social and curious in general. Both dolphins and porpoises do not breathe automatically, as we do; they must consciously take each breath. So how do they sleep, having to tell themselves to breathe? Although researchers still don't fully understand how they do it, a study of dolphins showed they can alternate slow wave sleep for half of their brain at a time (unihemispherically) while the other half stays active.

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