If approached by someone decked out in snorkeling gear, would you say hello, or just avoid them? That’s one situation that behavior ecologist Bruno Díaz López posed to bottlenose dolphins in Italy’s Gulf of Aranci.
Using photoidentification surveys, Díaz López studied 24 dolphins between 2004 and 2011. The dolphins were introduced to something unusual—either a scuba diver or a shrill noisemaker—and Díaz López found that each had a consistent reaction over time. Some are bold, quick to approach the person or noisemaker, and others are shy, giving the threatening intruder a wide berth. Some dolphins fell somewhere in the middle.
“We’d known that dolphins have these personalities from captive studies, but that is not their normal lives,” Díaz López, also the director of the Bottlenose Dolphin Research Institute in Pontevedra, Spain, tells National Geographic’s Virginia Morell. “Now, we know wild dolphins have personalities, and that these are important in their social system—as they are in ours.”
The new research, published in the journal Animal Behavior, adds to an ever-growing body of knowledge about dolphin behavior. The cetaceans live in social groups that vary in size and often change over time as animals leave or join in, making them “fission-fusion” groups.
Research has shown that dolphins’ social groups are incredibly complex, and in some ways, similar to ours. Earlier this month, a study showed that pairs of males travel together and sing in sync to attract mates. Other research provided evidence that dolphins call each other by name and grieve their dead.
In 2018, researchers with the Morigenos-Slovenian Mammal Society found that groups of dolphins near the coast of Slovenia found a way to avoid each other but share a favorite feeding area every day. In that study, each of the two groups of dolphins had core “cliques” that were only seen together four times in 16 years, Atlas Obscura’s Anna Kusmer reported. Animals outside of the core clique were “tiered” by how often they interacted with the core group, ending with lonely stragglers that weren’t bonded to either group specifically.
The new dolphin personality study looks at each dolphin individually to understand how its personality affects the group dynamic—Díaz López even mapped out the dolphins’ relationships in the 24-animal group. Males and females were bold and shy in similar amounts. Bold dolphins seemed to play favorites, showing a preference for certain companions. And Díaz López tells National Geographic that because bold dolphins enjoy the company of others, they may be the ones spreading information in the group, too.
“The study should be applauded for demonstrating these expected links in real life, where getting the data is super-challenging,” Tel Aviv University behavioral ecologist Orr Spiegel, who wasn’t involved with the study, tells National Geographic.
But the study does not address a pressing concern: the evolutionary benefit of personalities in dolphins, as University of Exeter behavioral ecologist Sasha Dall tells National Geographic.
The noisemaker that Díaz López used in the study is intended to keep dolphins away from fishing nets to prevent them from taking the catch from fishermen, and stop them from getting caught in the net themselves. But as Díaz López told Faro de Vigo’s Manuel Mendez, the devices may do more harm than good, not only introducing noise pollution to the area but also inadvertently training the dolphins to think of it as a dinner bell.
And once a bold dolphin figures that out, it might tell all of its friends.
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