Dolphins are highly social animals. Physical contact and gentle caresses are ways to maintain this sociability. It is not the only technique they use. Why do male dolphins whistle? To maintain, also, their social relationships with weak allies. So says the University of Bristol.

Strengthening partnerships
The magazine ‘Current Biology’ publishes the finding. It says that dolphins have mild vocal exchanges with non-close allies. Nine years of acoustic and behavioral data from a dolphin population in Shark Bay, Western Australia, were used.
Lead author is Emma Chereskin, Bristol School of Biological Sciences. “Many animals use tactile contact to reinforce and reaffirm important relationships. If the number of close social relationships increases, so do the demands on available time and space. Male bottlenose dolphins form multilevel strategic alliances. We wanted to know how they maintained multiple alliance relationships in large groups.”
Dr. Stephanie King, also of Bristol, explains how dolphins forge alliances. “Strongly bonded allies involved a petting relationship and frictions. Weakly bonded allies engaged in more hissing exchanges. These weaker, social relationships can be maintained with vocal exchanges.”

Talking instead of touching
In the social bonding hypothesis it is believed that vocalizations evolved as a form of “vocal grooming” substituting for physical grooming. The increasing size of groups meant that much time was available for physical contact.
This research brings something important to the point. Says Chereskin. Vocal exchanges can function as a replacement for physical bonding. Why do male dolphins whistle? Because it allows them to “bond at a distance”.
This evidence supports the social bonding hypothesis outside the primate lineage. Moreover, they raise exciting new questions about the origins and evolution of language.”