Common Bottlenose Dolphin

The dolphin everyone pictures: robust, gray, 2 to 4 m (6.5 to 13 ft), with a short thick beak, a tall curved dorsal fin and a permanent half-smile that is an accident of jaw shape and means nothing.

Each one has a name. In the first months of life a calf invents a signature whistle of its own and keeps it for decades, using it to announce itself and hearing it used by others to address it. Dolphins copy the signature of an absent animal to call it, respond to their own whistle played back through a speaker, and remember the whistles of companions they have not met for twenty years. It is the closest thing to a personal name documented in any animal outside our own species.

The rest of the behavior is built on the same social machinery: hunting is coordinated, prey is driven against sandbanks or into tight balls, and techniques are learned from the mother rather than instinctive, so neighboring groups do things differently.

Dorsal fins collect nicks and scars, and no two are alike, which is why photographs of fins are the standard census tool. A shot of a fin from a dive boat is genuinely useful data, and a shot of an animal's face is not.

We do not support keeping dolphins in captivity. These are animals that travel tens of kilometers a day, hunt in coordinated groups, hold societies with their own dialects, and stay with their families for life. A show pool reproduces none of it, and the noise, the chlorine and the boredom are not details - they are what kills them early. Many of the animals performing today were taken from the sea, and the drive hunts that supply them continue because the tickets sell. So do not buy one. No dolphinarium, swim-with-dolphins program or hotel show survives without paying visitors, and every one of them ends the day people stop coming.