Some sharks are 'gregarious' and have strong social connections, whilst others are more solitary and prefer to remain inconspicuous, according to a new study which is the first to show that the notorious predators have personality traits.
Personalities are known to exist in many animals, but are usually defined by individual characteristics such as how exploratory, bold or aggressive an individual is.
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 personalities, which determine how they might interact with group mates in the wild.
In a study published today in the journal Behavioral Ecology and Sociobiology, the team tested for social personality by recording the social interactions of groups of juvenile small spotted catsharks in captivity under three different habitat types.
The species of shark (Scyliorhinus canicula), found throughout the northeast Atlantic and Mediterranean, group together by resting around and on top of one another, sat on the bottom of the seafloor.
Working at the MBA in Plymouth, Devon, ten groups of sharks were monitored in large tanks containing three habitats which differed in their level of structural complexity.
Dr David Jacoby, a behavioural ecologist now at the Institute of Zoology, London 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 substrate in the bottom of the tank."
Professor Darren Croft, of the Centre for Research into Animal Behaviour at the University of Exeter, added: "We define personality as a repeatable behaviour across time and contexts. What is interesting is that these behaviours differ consistently among individuals. This study shows, for the first time, that individual sharks possess social personalities."
He added: "In the wild these small juveniles can make easy prey items 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."
'Shark personalities? Repeatability of social network traits in a widely distributed predatory fish' by David Jacoby, Lauren Fear, David Sims and Darren Croft is published today in the journal Behavioral Ecology and Sociobiology.
The work was funded by the Fisheries Society of the British Isles.
About the University of Exeter
The University of Exeter is a Russell Group university and in the top one percent of institutions globally. It combines world-class research with very high levels of student satisfaction. Exeter has over 18,000 students and is ranked 8th in The Times and The Sunday Times Good University Guide league table, 10th in The Complete University Guide and 12th in the Guardian University Guide 2014. In the 2008 Research Assessment Exercise (RAE) 90% of the University's research was rated as being at internationally recognised levels and 16 of its 31 subjects are ranked in the top 10, with 27 subjects ranked in the top 20. Exeter was The Sunday Times University of the Year 2012-13.
The University has invested strategically to deliver more than £350 million worth of new facilities across its campuses in the last few years; including landmark new student services centres - the Forum in Exeter and The Exchange on the Penryn Campus in Cornwall, together with world-class new facilities for Biosciences, the Business School and the Environment and Sustainability Institute. There are plans for another £330 million of investment between now and 2016.
Images can be obtained from Guy Baker.
The Marine Biological Association (MBA) is a professional body for marine scientists with some 1,400 members world-wide. Since 1884 the MBA has established itself as a leading marine biological research organization contributing to the work of several Nobel Laureates and over 170 Fellows of the Royal Society. In 2013, the MBA was awarded a Royal Charter in recognition of its long and eminent history and its status within the field of marine biology. The award strengthens the Association's role in promoting marine biology as a discipline and in representing the interests of the marine biological community.