Sharks do have personalities, study finds

LONDON — Some sharks can be “gregarious” and have better social skills, while others are loners and prefer to remain hidden in the background, showed a new study which is the first to show that the much-maligned predators have different personalities.

Personalities are known to exist in many animals, but are usually defined by individual characteristics such as how bold or aggressive an individual is.

However, research led by the University of Exeter and the Marine Biological Association of the UK (MBA) has shown for the first time that individual sharks actually possess social and antisocial personalities.

The scientists found more sociable sharks stayed safe from predators by remaining within a large group, whereas less sociable ones were forced to use camouflage to blend into their surroundings to avoid predators.

In a study published in the journal Behavioral Ecology And Sociobiology, the scientists studied the behaviour of juvenile small spotted catsharks (Scyliorhinus canicula) in captivity in three different types of habitat. The species are found throughout the north-east Atlantic and Mediterranean and survive by grouping together on the sea floor. Working at the Marine Biological Association in Plymouth, Devon, 10 groups of sharks were studied.

Dr David Jacoby, a behavioural ecologist now at the Zoological Society of London (ZSL), said: “We found that even though the sizes of the groups forming changed, socially well-connected individuals remained well-connected under each new habitat. In other words, their social network positions were repeated through time and across different habitats.

“These results were driven by different social preferences (i.e social/antisocial individuals) that appeared to reflect different strategies for staying safe. Well-connected individuals formed conspicuous groups, while less social individuals tended to camouflage alone, matching their skin colour with the colour of the gravel in the bottom of the tank.”

Professor Darren Croft, of the Centre for Research into Animal Behaviour at the University of Exeter, added: “What is interesting is that these behaviours differ consistently among individuals. This study shows, for the first time, that individual sharks possess social personalities.

“In the wild, these small juveniles can make easy prey for larger fish, so different anti-predator strategies are likely to have evolved. More research, however, is required to truly test the influence of predators on social personality traits in sharks. This study is the first step in that direction.”

Prof William Hughes, an animal behaviour expert at the University of Sussex, said he was impressed by the level of detail in the results, reported BBC News. “They recorded which shark was hanging around with which other sharks, on a number of occasions across two days — so they got a very, very detailed picture of the social relationships.”

Likening the experiments to watching a group of people, he told BBC News: “Imagine if we took 10 work colleagues and plonked them in a bar, and observed which individuals sat with which other individuals over the course of an evening.”

Then repeat the experiments in a nightclub, and perhaps back at work — and then, repeating the whole exercise with nine other groups of 10 colleagues. Individual people would tend to form bigger or smaller groups no matter what the situation, much like the sharks.

“It’s a very nice piece of work. It provides some pretty reasonable evidence that sharks show a form of social personality,” Prof Hughes said.