Bottlenose dolphins form decadeslong male bonds and work together to help pals find mates, researchers have discovered.
The dolphin “wingmen” cooperate in sophisticated alliances to help one another pair off — and ward off competitors.
But most extraordinary is that the dolphins not only form associations within groups, but forge intergroup alliances in sophisticated social interactions only previously observed in humans, noted the researchers, who published their findings earlier this week in the journal Proceedings of the National Academy of Sciences.
“These dolphins have long-term stable alliances, and they have intergroup alliances: alliances of alliances of alliances,” University of Massachusetts Dartmouth behavioral ecologist Richard Connor, one of the paper’s authors, told The Guardian. “Before our study, it had been thought that cooperative alliances between groups were unique to humans.”
The research findings support the “social brain” hypothesis: that mammals’ brains evolved to be proportionately larger to develop complex social relationships.
Humans and dolphins are the two animals with the largest brains relative to their body size. “It’s not a coincidence,” Connor noted.
The scientists reached their conclusions by closely observing and listening to dolphins in intensive boat-based surveys from 2001 to 2006 in Shark Bay, Western Australia. They kept close tabs on 202 Indo-Pacific bottlenose dolphins, including during mating season.
They tracked alliances among several “first-order” associations of two or three male dolphins that sometimes grew to 14 members in second-level associations. The groups helped each other find females to herd and mate with. They also helped lure away females from other competing groups of dolphins — and together defended against attempts at “theft” of females by rivals. In addition, they joined forces with other groups to pursue mutual goals.
The tighter the group, and the more intense the bonds among males, the more success they had in attracting females, the researchers found.
The groups form when the dolphins are still young. Group members generally don’t reap the rewards of paternity until their midteens, researchers found.
Stephanie King, affiliate professor of animal behavior at the University of Bristol and another study author, noted in a statement: “Not only have we shown that male bottlenose dolphins form the largest known multilevel alliance network outside humans, but that cooperative relationships between groups, rather than simply alliance size, allows males to spend more time with females, thereby increasing their reproductive success.”
King called “cooperation between allies” in human societies “one of the hallmarks of our success” and a strategy clearly employed by dolphins.
Our “capacity to build strategic, cooperative relationships at multiple social levels, such as trade or military alliances both nationally and internationally, was once thought unique to our species,” she added.
Connor said it’s amazing how similar — and how different — humans and dolphins are.
“I would say that dolphins and humans have converged in the evolution of between-group alliances — an incredibly complex social system,” said Connor. Yet it’s “astonishing because we are so different from dolphins.”