jiggle does not respond to gravity. You can use a dynamic curve as a spline IK curve though. By constraining only the base of the curve, you can get the effect you're looking for.
Hey THINKR, thanks for the advice. I googled spline ik tutorial and found this : http://www.animationartist.com/2003/08_aug/tutorials/softbody_tutorial.htm. From what I got, the spline ik method uses bones, but does your curve method require bones in the ears to work, or can I just select vertices and do something with a…