You may not think of these graceful, sleek predators as the most social creatures, but a new study has found that sharks have different personalities that determine how they interact with other members of the same species. Some sharks are happy to hang out in groups and have strong social connections, whereas other, “loner” sharks prefer to keep to themselves. According to the researchers, this is the first study to demonstrate that individual sharks have social personalities. The work has been published in Behavioral Ecology and Sociobiology.
Individual personalities are surprisingly widespread in the animal kingdom. Differences in personality have been documented in at least 60 different species to date, from primates to dogs, birds to octopuses. Much research, however, has focused on individual traits such as curiosity, shyness and aggression, neglecting to investigate sociality.
To address this gap in our knowledge, a team of researchers from the University of Exeter and the Marine Biological Association set out to examine social personality in juvenile small-spotted catsharks (Scyliorhinus canicula). These model animals are found in Northeast Atlantic and Mediterranean waters and have been studied extensively in the past.
As vulnerable juveniles, these animals must pick a strategy to avoid being munched on by predators. The two most likely tactics that these animals could adopt are “safety in numbers,” i.e. sticking together in groups, or going solo and relying on camouflage to blend in with the surroundings. The team therefore wanted to see preferences for these different strategies and whether this changes in new environments.
For the study, the team investigated the behavior of ten different groups of animals, each containing ten sharks, by placing them in three different tanks. Some were complex habitats with lots of different structures inside, such as rocks and other features, whereas others were more simple, mainly consisting of gravel.
They found that although the sharks changed group size in the different environments, those that were socially well-connected and formed groups always stayed in groups, no matter the habitat. Similarly, those that preferred to stay on their own would do so in each different tank.
“These results were driven by different social preferences (i.e. social/antisocial individuals) that appeared to reflect different strategies for staying safe,” lead author Dr. David Jacoby said in a news release. “Well-connected individuals formed conspicuous groups, while less social individuals tended to camouflage alone, matching their skin color with the color of the gravel substrate in the bottom of the tank.”
While this study focused on one species in captivity, the researchers are interested in comparing their work with studies by other labs. One group in the Bahamas, for example, is already looking at lemon sharks in the wild and has some preliminary evidence to suggest that this species also displays personality differences.
[Via University of Exeter, Behavioral Ecology and Sociobiology, BBC News and The Independent]
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