(EM / 07-06-10)  A Spanish researcher and a Paraguayan scientist have presented the most complete and detailed European study about the sounds bottlenose dolphins emit in communication.

So far, the scientific community thought that dolphins’ beeps were the main sounds emitted by these mammals, and didn’t know the importance and use of pulsed sounds.

Researchers of Italian Bottlenose Dolphin Research Institute (BRDI), with base in Sardinia, have shown that these sounds are vital for social life and reflect their behaviours.

“Bursts of pulsed sounds in bottlenose dolphins’ life and their use during socialization and maintenance of hierarchical level prevent from physical conflict, which is also an important energy saving”, says to SINC Bruno Díaz, main author of the study, researcher and director of BDRI.

The investigation, published by Nova Science Publishers in the book 'Dolphins: Anatomy, Behaviour and Threats', presents the most complete European collection of these bursts of sounds and whistles collected by bioacoustics from 2005 in waters of Sardinia (Italy).

According to experts, tonal sounds or whistles (more melodic) allow dolphins to keep in contact (mainly contact among mother and offspring) and coordinate hunting strategies. Pulse sounds (more complex and varied than whistles) are used “to prevent from physical aggression in conditions of high excitability, for instance when they compete for the same food” says Díaz.

According to Díaz, bottlenose dolphins emit longer pulse sounds during predation and in times of high aggression: “they are the best and longer heard” and are used to maintain the hierarchical level of each specimen.

In the presence of other specimens that approach to the same prey, dolphins emit these strident sounds. The less dominant pulls out to avoid confrontation. “The surprising thing is that these sounds have a high unidirectionality, unlike human sounds. A dolphin can emit one sound to another specimen that is a competitor and this one takes the hint easily” the Spanish researcher has said.