Male Dolphins Make Friends Through Shared Interests Just Like Humans—and Bonds Can Last Decades

When humans make friends, we often choose companions who share similar traits to us or enjoy participating in the same activities that we enjoy.

Intriguingly, it turns out that dolphins may not be so different, according to a study published in the Proceedings of the Royal Society B which found that the cetaceans form strong social ties with those who have similar interests.

In some ways this may not be surprising, given that we know dolphins live in groups characterized by complex social interactions. Nevertheless, the latest findings are yet another poignant example of the intelligence that these creatures posses.

For the study, an international team of scientists from the University of Western Australia, the University of Bristol, U.K., and the University of Zurich, Switzerland, investigated a unique group of bottlenose dolphins.

This community—which lives in the World Heritage area of Shark Bay, Western Australia—is particularly intriguing because the females are known to use marine sponges as foraging tools, a behavior that hasn't been observed anywhere else.

The behavior, known as "sponging," helps the dolphins to find food in deeper waters and is socially-learned, being passed down from mother to calf,

Previous studies have shown that females in this group which use marine sponges to find food often like to hang out with other females who do the same. However, studies of this behavior in males are lacking, leaving a gap in our knowledge.

To try and address this gap, the researchers collected data on 124 male dolphins in Shark Bay over a 9-year period between 2007 and 2015. Among these individuals, some engaged in the sponging behavior, while others did not.

After analysing their data, the team came to the conclusion that that those males who used sponges for foraging associated significantly more often with other "spongers," regardless of how related they were to their companions. Interestingly, male spongers spent significantly more time foraging and less time resting than non-spongers.

"Foraging with a sponge is a time-consuming and largely solitary activity so it was long thought incompatible with the needs of male dolphins in Shark Bay—to invest time in forming close alliances with other males," Simon Allen, a co-author of the study from Bristol said in a statement. "This study suggests that, like their female counterparts and indeed like humans, male dolphins form social bonds based on shared interests."

According to lead author of the study, Manuela Bizzozzero from the University of Zurich, the findings cast new light on the social alliances between male dolphins at Shark Bay.

"These strong bonds between males can last for decades and are critical to each male's mating success," she said in the statement. "We were very excited to discover alliances of spongers, dolphins forming close friendships with others with similar traits."