Such observations, along with others showing, for example, how dolphins could co-operate with military precision to round up shoals of fish to eat, have prompted questions about the brain structures that must underlie them.
This was one of the segments they showed a couple of times on the BBC Life series. One dolphin kicks up circles of sand from the ocean floor around a school of fish, and the other dolphins wait outside the circle. The fish panic because they can't see where they're going, and they attempt to leap over the obstruction--right into the waiting dolphins' mouths. Forking brilliant.
If this isn't an example of animals working in teams and employing reason, I don't know what is.