One reason for imitating another dolphin's whistle may be to make contact with that dolphin and get its attention within a large group. Preliminary research seems to bear this idea out although details of the exact social contexts under which dolphins imitate another's whistle are still under investigation. Dolphins may use other sounds besides whistles to communicate. Courtship behavior can yield pulsed yelps. When under duress dolphins emit pulsed squeaks.
Aggressive confrontation can produce buzzing click-trains.
The generally poorer visibility found underwater prevents dolphins from communicating visually over any distance. However, when close to each other, body language may play a role in dolphin communication. Below is a list of dolphin behaviors possibly used for visual communication. Researchers are still studying the behaviors and situations when dolphins use body language to learn specifically what they mean. Bend head and tail ventrally.