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Male dolphins whistle to maintain social relationships

Dolphins are intriguing mammals with complex social behaviors and relationships. Researchers at the University of Bristol have found that male bottlenose dolphins maintain social relationships through whistle exchanges. 

Previously, male dolphins have been known to use physical contact like petting to connect with strongly bonded allies. This new research shows that male dolphins can also use different tactics to connect with weaker allies through vocal exchanges. 

“Many animals, including humans, use tactile contact, touch, to strengthen and reaffirm important relationships. But as the number of close social relationships increases, so too do the demands on the time and space available for relationship maintenance through physical contact,” said study lead author Emma Chereskin, from Bristol’s School of Biological Sciences.

“Male bottlenose dolphins form strategic, multi-level alliances, and we wanted to know how they maintained multiple alliance relationships in large groups.”

To better understand how male dolphins maintain relationships, the scientists relied on nine years of acoustic and behavioral data from Shark Bay, a dolphin population in Western Australia.

Groups of males were followed so that researchers could observe their physical and acoustic behavior. By doing so, the research team was able to identify the different approaches to bonding. For example, within dolphin alliances, bonded dolphins engage through physical contact, whereas those that are weakly bonded engage through whistle exchanges. 

“This illustrates that these weaker but still key social relationships can be maintained with vocal exchanges,” said study senior author Dr. Stephanie King.

The social bonding hypothesis proposes that vocalizations and language have evolved as a form of ‘vocal grooming’ to replace physical grooming as larger groups make physical contact more demanding and can take up more time. This hypothesis does differ when applied to primates, as studies suggest that vocal exchanges among primates happen between bonded individuals and don’t necessarily replace physical bonding.

The study provides new evidence that vocal exchanges can serve as a method of bonding – “but more importantly, and in line with the social bonding hypothesis, that vocal exchanges can function as a replacement of physical bonding, allowing allied male dolphins to ‘bond-at-a-distance’. This evidence in support of the social bonding hypothesis outside of the primate lineage raises exciting new questions on the origins and evolution of language across taxa,” said Chereskin,

The research was funded by The Branco Weiss Fellowship – Society in Science and the National Geographic Society.

By Katherine Bucko, Staff Writer

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