Much like humans, dolphins primarily use sound to convey information to one another. The sound is described as "whistling" by the Dolphin Research Center. Dolphins use visual cues and body language to communicate although less often.
Dolphins are widely regarded as one of the most intelligent species within the animal kingdom. As such, their social interactions and communication are extremely complex. Dolphins often use sound to identify, locate and convey information to one another. Additionally, these "whistles" are used to communicate dolphins' emotional and mental state, according to the Dolphin Research Center.
Dolphins also communicate visually through gestures and touch. Common forms of body language observed in dolphins include arching, eye-rolling, flexing, head shaking and playing dead. Different forms of physical contact also seem to play a role in dolphin communication. Overlapping pectoral fins, pushing, bumping, ramming, biting, nuzzling, patting, tooth raking, rubbing and tail kicking are all behaviors believed to be communications between dolphins. The Dolphin Research Center states that some of these forms of physical contact are considered to be acts of aggression.
Discovery News claims that although dolphin cries sound like whistles, dolphins do not actually whistle when they communicate but instead speak to one another in ways similar to humans. This assertion is based on the physiological processes that dolphins use to create communicative sounds and how those processes are physiologically similar to the way human vocal cords are used.