Dolphin carry on conversations with each other. So do porpoises and,probably,other whales. They make a great variety of sounds, mainly clicks and whistles,which are produced by complex group of air sacs and valves in the head. [They do not have vocal chords like man's] If one dolphin of a group is caught in a trap,it appears to warn the others,not just of general danger,but specifically what and where the danger. The dolphins then seem to discuss how to release the trapped one and carry out their plan.