My sens do this now... It's amazing to watch this behavior. They've only done it with nightcrawlers. One will usually grab one end and swim away with it, then another will pick up on it and grab the other end... A tug-of-war insues, followed by an unimaginable death roll by both.
The first time they did it I was shocked. They were smack-dab in the center of my tank, up in "mid-air" spinning furiously. I couldn't even count the revolutions.