Nature
PUBLISHED
New research published in Proceedings of the Royal Society B has revealed that sharks are a lot more social than we realize. A team of scientists observed the behavior of grey reef sharks around the Palmyra Atoll and found that these sharks had associates who they would return to after solo journeys and that they existed in communities rather than as lone swimmers. The study spanned over four years and some of the sharks observed stayed together the entire time.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Using acoustic tracking tags, which are essentially shark-mounted radios that indicate when individuals come within a certain range, and animal-borne cameras, a team of researchers joined up with the Zoological Society of London (ZSL) to analyze a group of 41 sharks. Together they formulated a new analytical model that could pick up on social patterns within the datasets. Their findings were presented in a color-coded social network, which showed that there were tight and tangled social groups among the sharks, with certain individuals choosing to spend their mornings with specific groups before dispersing throughout the day and reconvening with their buddies later on.
As well as returning to the same groups, they were also found to return to the same locations and, as Yannis Papastamatiou, study author from the Florida International University, highlights, the most obvious explanation for this is socializing. “Using one part of the reef helps you find your friends, so to speak,” Papastamatiou said in a statement. “It can be hard to maintain social bonds when you live in the ocean, but if sharks all routinely return to the same spot on the reef then that will help them maintain their group structure.”
So how do you pick up on a shark socializing? It’s not as if they call out fun nicknames for each other or get particularly up close and personal. It turns out, however, that sharks do socialize in their own, rather more perfunctory way. Using the analytical model, the researchers were able to identify differences between chance encounters with other sharks and purposeful interactions with group members. The study authors highlight, however, that this isn’t the sort of friendship that Queen sang about but rather more an association that likely benefited the sharks in gleaning more information from their environment, be it about predators or where food can be found.
“For some time now, we have known that sharks are capable of having distinct social preferences for other group mates,” said David Jacoby from ZSL in a statement. “We had no idea, though, that these social bonds could last for multiple years or that in the absence of reproduction or parental care that such communities might function as areas to exchange information.”
This rare insight into the elusive social behavior of sharks has revealed new ways in which the species can be protected, as group animals can sometimes be more vulnerable to overfishing and predation. Losses of entire groups could have devastating impacts on an overall community of sharks, especially when these associations help other members find food, as the study suggests.
