Male dolphins boost their social lives by whistling to each other at a distance, according to new research.

The high pitched sound tells others they are present and wish to make contact. It helps the marine mammals maintain key community ties, say scientists, describing the rarest type of social organization in the animal kingdom.

And, now, reports Science.org, researchers report this male bonding has a big evolutionary payoff: Dolphins with the strongest buddy bonds actually father more offspring.

Comparing genetic data collected from these males, an evolutionary biologist at the University of New South Wales, Sydney, determined that males who had the strongest social bonds and were friends with all members of their alliance had the most offspring.

Lead author Emma Chereskin of the University of Bristol says, "By forming strong alliances with others, males can influence their own reproductive success in a way that wouldn't be possible as single individuals."

"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."

"We wanted to know how they maintained multiple alliance relationships in large groups."

Language evolved to support long-distance social bonding. They are also known to use physical contact, such as gentle petting, to connect with strongly-bonded friends.