Some sharks are loners, others are gregarious

 Just as people exist on a sliding scale of sociability -- some seeking out and thriving in the presence of others, some preferring personal space and solitude, others somewhere in between -- sharks, too, have personalities.
That's the conclusion of a team of researchers from the University of Exeter and the Marine Biological Association who recently monitored several groups of juvenile small-spotted catsharks in captivity. The groups were observed in three different habitat types -- each with varying degrees of structural complexity -- allowing researchers to see how group dynamics changed over time and place.
The researchers found that more sociable individuals remained so, regardless of the changing surroundings and makeup of the group. More individualistic, loner-type specimens continued to stick to themselves throughout the study.
"We found that even though the sizes of the groups forming changed, socially well-connected individuals remained well-connected under each new habitat," study author Dr. David Jacoby, a behavioral ecologist, said in a press release. "In other words, their social network positions were repeated through time and across different habitats."
The shark species being observed, Scyliorhinus canicula, socialize by resting atop each other along the ocean floor; they are found throughout the waters of the northeast Atlantic and the Mediterranean.
Research has shown a number of other animals to possess distinct individual personalities, but most studies focus on passivity, aggressiveness and inquisitiveness -- social personality traits in animals is a less explored field of research.
"We define personality as a repeatable behavior across time and contexts. What is interesting is that these behaviours differ consistently among individuals," added Professor Darren Croft, an expert in animal psychology at the University of Exeter. "This study shows, for the first time, that individual sharks possess social personalities."
The study was published this week in the journal Behavioral Ecology and Sociobiology.