DAILY SCIENCE

The surprisingly social lives of manta rays
Warm, fuzzy insights into the social lives of animals have tended to involve creatures other than fish. Might manta rays help flip this script?
September 25, 2019

The more scientists learn about the social lives of animals, the easier it is for people to relate to them. A species might be particularly beautiful, or have an unusual life history or extraordinary physiology—but it’s the bonds between individuals, the relationships and community, that most warm our hearts.

Those social insights have tended to involve charismatic creatures: orca and elephant families guided by their matriarchs, young crows staying home to help their parents raise newly-hatched siblings, loyal wolf packs. As for fish, however, they’re not usually considered social in meaningful ways. They might swim in schools, but that doesn’t necessarily imply a deep individual connection.

Might manta rays help flip this script?

In a study published in the journal Behavioral Ecology and Sociobiology, researchers led by Robert Perryman, a biologist with the Marine Megafauna Foundation, gathered data on more than 500 groups of reef manta rays off the western coast of New Guinea. The observations were deep and detailed, spanning five years and identifying rays on an individual basis. The resulting maps of their social networks showed that manta ray groups didn’t form randomly or by happenstance; rather, individual manta rays preferred the company of certain rays more than others.

“We show for the first time that individual manta rays have preferred relationships with others that are maintained over time, and structured societies,” write Perryman and colleagues. What’s more, “overall network structure was characteristic of a dynamic fission-fusion society”—individuals moving between different groups that split and come together again, as do elephants and crows and, for that matter, humans.

Though the findings might be construed as implying that manta rays have friendships, the researchers were careful not to use that term. Affiliations with preferred individuals tended to last for just a few weeks or months—certainly not an insignificant time, but not an especially long duration for creatures who can live 20 years or more. To Perryman, the word “friendship” implies something longer-lasting. “I think ‘acquaintances’ is probably a better word,” he says.

Yet even to think of manta rays as having meaningful acquaintances is a novelty, implying an experience of life that overlaps in an important way with our own. (Giant manta rays, a species closely related to reef mantas, may also recognize themselves in mirrors, a feat generally recognized by scientists as indicating human-style self-awareness.) Perhaps appreciating that could motivate people to care more about their plight; fishing, climate change, and pollution have caused massive population declines in both reef and giant mantas, who are now considered in danger of extinction.

“Anything that resonates with the way that we, as people, live our own lives,” says Dan Franks, a study co-author and biologist at the University of York, “does make people empathize more with them.” As different as humans are from those aquatic giants, we still have things in common.

Source: Perryman et al. “Social preferences and network structure in a population of reef manta rays.” Behavioral Ecology and Sociobiology, 2019.

Image: Henrik Winther Andersen via Flickr

 

About the author: Brandon Keim is a freelance journalist specializing in animals, nature and science, and the author of The Eye of the Sandpiper: Stories From the Living World. Connect with him on Twitter, Instagram and Facebook.

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