Dolphins are capable of imitating certain sounds very accurately and often learn other dolphins' whistles. One reason for imitating another dolphin's whistle may be to get its attention within a large group. Preliminary research seems to support this idea although details of the exact reason for imitation 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.