When some bottlenose dolphins are hunting their dinner, they use their tails to stir up the mud on the seafloor to construct a circular jail to trap their prey. See them do it in the video below. Scientists have observed the behavior in the Florida Keys and now they've seen it in Caribbean dolphins as well. Dolphins sure are smart. From New Scientist:
A "ring maker" dolphin circles near the ocean floor and traps fish behind a ring of mud as others lie in wait with The mud ring hunting strategy is a case of blindsiding prey. A "ring maker" dolphin circles near the ocean floor and traps fish behind a ring of mud as others lie in wait with mouths open, and lunge to catch any fish attempting to escape the mud by jumping out of the water.
