Communication between dolphins is based on touching, visual contact and sound exchange. Dolphins emit a full range of sounds that are used to interchange messages with other dolphins and to orientate themselves (bio radars).
The newspaper The Observer has denounced in September 2005 that with the hurricane Katrina almost forty US army trained dolphins were liberated. Those dolphins had been trained to identify sub aquatic spies or to shot against terrorist. The US army has recognized that they had been training dolphins in order to military purposes.