This article originally appeared on VICE US.
Dolphins are socially complex creatures. They form cliques, shun rivals, and even dole out nicknames. They also create friendships over common interests, much like humans do, according to new research.
An investigation of Indo-Pacific bottlenose dolphins in Western Australia’s Shark Bay revealed that males prefer each other’s company while foraging for food, and forge friendships based on their preferred tool for the job.
Shark Bay’s dolphins are known for their tool use—specifically the use of sea sponges to cushion their beaks as they root around the ocean floor for fish. The behavior of these “spongers” was observed by scientists in the new study.
Data collected from 124 male dolphins over nine years showed that spongers associated with one another based on their mutual interest in foraging techniques. Those who fed this way spent more time together than those who did not, according to findings published on Wednesday in the Proceedings of the Royal Society B.
“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 senior research associate at the University of Bristol’s School of Biological Sciences and co-author of the study, said in a statement.
The team looked at a subset of 13 spongers and 24 non-spongers between 2007 to 2015. Their analysis showed that while spongers were attracted, non-spongers also formed alliances, and both groups socialized for equal proportions of time.
This type of bonding has been previously observed in Shark Bay’s female dolphins. Janet Mann, a behavioral ecologist at Georgetown University who has studied this population, suggests that sponges are mostly used by females, due to “selective pressures they face while raising a calf as long as they do.” Foraging around rocks could yield prey that other dolphins are unable to find, Mann said.
The new research offers new insight into the lives of male dolphins.
“These strong bonds between males can last for decades and are critical to each male’s mating success,” Manuela Bizzozzero, an evolutionary geneticist at the University of Zurich and lead author of the study, said in a statement.
“We were very excited to discover alliances of spongers, dolphins forming close friendships with others with similar traits,” Bizzozzero said.