Other Animals and Nature
Date: 18 June 2008
Dolphins have been observed to create bubble rings by exhaling air carefully in the middle of the vortices caused by the motion of their fins through the water, among other techniques.
Besides being nice to look at (and a neat demonstration of fluid mechanics), this phenomenon also might throw some light on dolphin cognition, since the skill to create the rings is a bit subtle and tends to be taught from one dolphin to the next via careful observation and practice. I'm also intrigued by the report that they seem to be using sonar to locate the vortex in the water, since that would be a fairly amazing bit of audio analysis.
Imagine a beautiful, crystalline bubble ring that hovers angelically in the water, big enough for a dolphin to swim through and flexible enough to be divided into smaller rings that can then be grown into larger rings.
Amazing, but how is it made? To create the bubble ring, the dolphin first uses one of its flippers to create a spinning ring of water called a "vortex ring."
Next, the dolphin blows a giant air bubble directly into the ring. As the air bubble increases in size it's flattened by the weight of the water above it.
As more air is blown into the bubble, water seeps in as well. The water seeping in from below eventually forms a fountain that shoots through the center of the bubble. When it breaks through the top of the bubble, a ring of air is left behind, held together by the force of the water spinning around it.
It's so stable in fact that it can be broken apart into smaller rings, which can then be inflated to form larger rings.
[Note: this info comes from 2 other web sites - sorry I don't have their links to add here]
Click on the link below to view the video.