SYDNEY, Oct. 22 (Xinhua) -- One of the ocean's most feared predators, the great white shark once thought to be a solitary hunter, are seen to occasionally form distinct groups which they will revisit over periods of years, Australian researchers said on Tuesday.
Most of the year round, great whites are solitary predators but will group together to feast on baby seals at certain times of the year.
Previously thought to be a random occurrence, prolonged observation showed that the groups actually consist of many of the same members who return together year after year.
Behavioural ecologist Stephan Leu from Macquarie University, along with colleagues from Flinders University and the Fox Shark Research Foundation, as well as French government research organisation CNRS, spent four and half years monitoring about 300 white sharks gathered around a seal nursery in the Neptune Islands on Australia's southern coastline.
"We were able to identify what the co-occurrence is, that it's non-random. That certain individuals frequent the Neptune islands at the same time, more often than what you would expect by chance," Leu told Xinhua.
"What we don't know is what drives this, why are they doing this?"
It was originally believed that the gatherings were the result of individual sharks turning up in the same area at the same time, drawn by the presence of abundant food.
However by analysing thousands of photos taken from an underwater cage, married with network analysis techniques, a pattern driven by something other than chance began to emerge.
Leu said that so far the study authors hesitated to call the interactions 'social' as the evidence only shows that the sharks were in the same area at the same time, rather than interacting with one another.
"We're shying away from saying that it's a social interaction because the photos were taken not with a timestamp, but per day," he said.
"So it is sharks occurring at the same place during the same day, but because it's not a photo where they're side by side that's why we're pretty strict about not calling it social and rather calling it co-occurrence."
Leu said that the team will continue to study sharks at Neptune Island to discover more about their behaviours.
