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Southern Right Whales often put their tail in the air and sail.
Photo: Iain Kerr

April 7, 2002
"Animals That Sail"
  Real Audio
  28k

Last night after dinner we hung a bright light over the side to see what would come. After a while along came a wonderful surprise: a by-the-wind sailor, a little, flat, oval, hydroid colony, called Velella-it's a cute little shaboobie-doobie about one and a half inches long colored the same sky-blue as the Portuguese Man-of-War (or the "blue bottle" as they are called here in Australia).

Sticking up above its flat, oval, air-filled, raft-like base is a clear hardish, triangular sail. In the center of it and at the peak of the triangle is what looks for all the world like the tip of a little mast. It's a tiny sailboat with a cutter rig (i.e. fore and aft sails of about the same size as a sloop but with the mast further aft). Velella sails about the ocean dragging its tentacles through the neuston layer, the top few millimeters of the sea-the layer of sea water in which microscopic life is most abundant.

The Portuguese Man-of-War jellyfish also sails, but it has a Lateen rig (the kind you see on Arab dhows) while Velella has a marconi rig. The sail on Velella is fixed but the Portuguese Man-of-War can tack while sailing downwind-which is to say that they can trim their sails like sailboats. I've watched them do it. The sail seems to slowly deform downwards but then slowly re-erects itself in a modified form that achieves the other tack.

Both these creatures catch their prey with stinging cells. The Portuguese Man-of-War has long tentacles that hang down many meters and can paralyze tiny fish which it then draws up to its many mouths to eat. In Velella, however, very short tentacles called zooids fringe its oval, flat body. They contain stinging cells that sting to death and pass to the central mouth for eating whatever collides with them. So Velella has a totally different objective in sailing than we do. I have nightmares about the Odyssey colliding with something at sea, whereas Velella sails solely in order to collide with things at sea: its microscopic prey.

I have known about Velella for 47 years and have always wanted to see one. That's because I find it fascinating that so few animals sail as a means of getting around when it seems like such an effortless way to cruise the oceans, and so particularly well suited for making long passages; one simply sets their sail and steers; there is no need to expend any other energy. Other than jellyfish, there are very few other animals besides humans that sail. I've never been able to figure out why. Right whales sail by holding up their tails and letting the wind blow them along, but they seem to do this only as a form of play.

Just like the Incas, who, although they invented the wheel, are sait to only have used it in their toys, and never insofar as is known for practical things like carrying heavy loads over their long and exquisitely paved mountain highways. The fact that whales don't sail to make passages, or for any other practical function seems strange since sailing would seem to be so ideally suited for an animal like a whale, which migrates for thousands of kilometers without being able to refuel. How strange that when at last we encounter this behavior in mammals that it should be whales that perform it, and that they should do it only in play. Incas, these whales.

A Velella displayed in a glass.
Photo: Chris Johnson

By the way: though tail sailing is not used for serious travel whales seem to have another way of extracting motive power from the wind. Waves are generated by wind, and whales appear able to get an assist from the energy in waves during their migrations. Whalers have traditionally cut off the fluke tips of every whale they kill, claiming that during the time the catcher boat is off looking for more whales, the body of a dead whale whose fluke tips have not been cut off will swim for several miles, often causing it to be lost (in the present day, corpses are marked with a radio beacon so they can be recovered). Biologists used to pooh-pooh this practice as being a whalers' superstition. However, it has now been shown mathematically that propulsive forces on the tails of whales are indeed generated by ocean waves, and it now seems clear that whales can get a very significant assist from waves while making their long migrations.

Next time I'll tell you about he supreme sailors of the world-animals that sail in three dimensions not just two the way jellyfish and humans and right whales do.

This is Roger Payne speaking to you from the Odyssey with albatrosses in view.

(c) 2002 Written by Roger Payne

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