Quite a few fan holts out there have wavedancer (dolphin) companions. Here's a little summary about dolphins on this earth to help us understand these fine soft-skinned friends.
There are literally dozens of species of dolphins: the large black-and-white orca, the spotted dolphin, the spinner dolphin, and so on. The information here is based mainly on the bottle-nosed dolphin, which is widely known because they live along the shoreline (where people are more likely to come in contact with them) rather than in the middle of the open ocean. However, much of it applies to the other species as well.
Dolphins are mammals, of course, like we are, so they are warm-blooded and must come to the surface regularly to breathe air. (Usually two or three times a minute-and it only takes three tenths of a second to expel the used air and take a fresh breath!) Bottle-nosed dolphin adults are two to three and a half meters (7 to 12 feet) long (this varies for other species) and live 30 to 40 years (the larger orcas can live into their sixties). They are among the fastest animals in the ocean (comfortably reaching speeds of fifteen kilometers per hour [25 miles per hour]), and can dive down to depths of 60 to 90 meters (200 to 300 feet) for five- to eight-minute jaunts. Their streamlined shape, naturally, makes them fast, but the really amazing thing is that they can change their shape slightly as they travel at different speeds-always using the shape which presents the least resistance to the water at that speed. They have a layer of blubber under their skin that helps fill out their streamlined shape and insulate them from cold. This blubber layer is so essential that it is not used as a food store when the animal goes hungry. A starving dolphin will lose fat deposits in the neck while the blubber on the rest of the body remains as smooth and even as ever.
Incredibly streamlined animals, the dolphins don't have any external genitalia. Both males and females have a slit on the bottom of their tail, concealing the genitals within. Males can erect their penis at will, and in captivity can even learn to do so "on command" at a human's signal. Females additionally have a mammary slit on either side of the genital slit, enclosing the nipples. In the forehead of all species is a bulge called the melon.
Dolphins have an astonishing sonar capability. They send out a series of clicks, so short and close together that they sound like a single continuous noise to us, although they are usually outside our range of hearing. (The melon contains a jellylike substance that serves as a lens to focus the sonar beam forward.) The echoes that bounce off the dolphin's surroundings give the dolphin a 3-D picture in remarkable detail. Using sonar alone, they can tell the difference between an aluminum disk three millimeters (one-eighth of an inch) thick and a copper disk of the same size from fifteen meters (fifty feet) away. Dolphins have good eyesight, too, but sonar obviously has some advantages over vision. First, it can be used in the dark just as well as by day. It can be used in cloudy or murky water as easily as clear water. Second, since sound waves penetrate things that light doesn't, dolphins can essentially "see inside" many objects and surfaces. For example, one day, a dolphin seemed particularly excited and swam around a woman who worked at a water park, aiming sonar clicks at her abdomen. A doctor visit a week later confirmed the woman's pregnancy. (Could unborn dolphins possibly "see" the outside world by using sonar? I think it is impossible, since the sonar clicks are created using air trapped within cavities near the trachea. The cavities will have no air until the infant is born and takes its first breath. However, none of my reference sources specify at what age dolphins begin using sonar, so who knows!) Another anecdote I can't resist repeating is the case of a man who was a guest at a "swim with the dolphins" retreat. The human employees noticed the dolphins gathering around behind this particular man and curiously scanning the man's buttocks. When asked if there was anything strange about his rear end, the man replied, "Oh, I still have some shrapnel from a war wound there."
The drawback to sonar is that the animal emitting sonar clicks is essentially broadcasting his or her location and speed to everyone in earshot. Not something you want to do when you need to be stealthy! Orcas hunting seals, for example, maintain silence and hunt by sight alone. But generally, a dolphin at ease will emit a sonar burst every so often to check out the immediate surroundings.
Well, I'm sorry that I have written too many words already and I've only talked about the mechanics of being a dolphin. So the title of this article is incorrect-this isn't even close to "everything." And the implication of the title is misleading too, <wink> because it will have to be another time that I talk about the sex lives of dolphins, as well as the other aspects of their social behavior and lifestyle. Next issue, however, I'll return to astronomy with "The Wandering Stars."
Selected Bibliography:
© 2000
linda_tam@alumni.hmc.edu
Initially posted on July 1, 2000
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