Bottlenose dolphins speak the language of diplomacy to keep the peace when hunting in groups, research has shown.

The creatures use short vocal bursts to communicate messages that avoid conflict at times of high excitement and aggression, say Italian scientists.

Previously, experts were unaware of the importance of the sounds, which differ from the usual "whistles" emitted by dolphins.

"Burst-pulsed sounds are used in the life of bottlenose dolphins to socialise and maintain their position in the social hierarchy in order to prevent physical conflict, and this also represents a significant energy saving," said study leader Bruno Diaz, from the Bottlenose Dolphin Research Institute in Sardinia.

Whistles are used by dolphins to stay in contact with each other and co-ordinate hunting strategies.

The "burst-pulsed" sounds are more complex and varied. They are produced when dolphins are in close proximity to other individuals moving towards the same prey, the Italian scientists discovered.

In response to the sounds, less dominant members of the group move away to avoid conflict with the leaders.

"The surprising thing about these sounds is that they have a high level of uni-directionality, unlike human sounds," said Dr Diaz.

"One dolphin can send a sound to another that it sees as a competitor, and this one clearly knows it is being addressed."

The research, published in a new book Dolphins: Anatomy, Behavior And Threats, was carried out in the waters off Sardinia.