Intricate communication strategies seen in male dolphin alliances
It’s a well-known fact in the marine biology community that male bottlenose dolphins sometimes form long-lasting cooperative alliances with each other. These alliances can last decades, and have been the subject of intense study for decades as well.
Now, a new study in Current Biology puts together over 30 years of continuous research on this subject. Stephanie King, of the University of Western Australia, and colleagues wanted to better understand the role that vocal communication plays in coordinating complex social behaviors – such as cooperation – in bottlenose dolphins.
To assess the role of vocal signals, the researchers went to Shark Bay, Australia and recorded the dolphins’ vocalizations using underwater microphones. They then determined the individual vocal label used by individual males, and measured the similarity of those identity signals within and between alliances in order to determine whether males with stronger social relationships used vocal labels that were more alike.
“We found that male bottlenose dolphins that form long-term cooperative partnerships or alliances with one another retain individual vocal labels, or ‘names,’ which allows them to recognize many different friends and rivals in their social network,” says King. “Our work shows that these ‘names’ help males keep track of their many different relationships: who are their friends, who are their friend’s friends, and who are their competitors.”
The researchers wanted to know if allied dolphins shared similar calls as a way to advertise their alliance, or if they stuck to individual vocal labels. Analysis determined that males in an alliance kept their distinct vocal labels, which suggests that these calls may serve a purpose similar to an individual name. This finding is in contrast to other species, whose individuals with close relationships converge on shared vocalizations in order to advertise their alliance to that partnership or group.
“With male bottlenose dolphins, it’s the opposite – each male retains a unique call, even though they develop incredibly strong bonds with one another,” King explains. “Therefore, retaining individual ‘names’ is more important than sharing calls for male dolphins, allowing them to keep track of or maintain a fascinating social network of cooperative relationships.”
The researchers are planning to further study male dolphins’ relationships with one another more closely. They plan on playing the “names” of individual males back to each other and seeing how males respond to members of their alliances in different contexts. “It will be interesting to reveal whether all cooperative relationships within alliances are equal or not,” says King.
Image Credit: Simon J Allen at the Dolphin Alliance Project