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Great whites bite more often than thought

By Tim Jeanes
Great White Shark

The study examined the eating habits of 12 sharks off Neptune Island.

file photo: AFP

In an alarming finding for swimmers, new research has suggested one of the most feared marine creatures needs to feed much more often than previously believed.

A team from the University of Tasmania has studied 12 great white sharks near Neptune Island off the South Australian coast.

Waters off the island attract sharks that feed on seal pups from the nearby colony.

The research aimed to shed light on the eating habits of the creatures which scientists say are poorly understood.

Marine biologist Jayson Semmens says 1980s American research suggested the sharks could survive for about six weeks on a single 30-kilogram meal.

Dr Semmens says the new study shows sharks can only go up to 15 days between meals of that size, debunking the older research.

"They picked a shark that probably wasn't working very hard at the time when they did it," he said.

"At the time it was a really novel study. They did some metabolic work similar to us but on one shark and they suggested that a white shark only needed to feed every six weeks.

"That idea had really perpetuated itself through the community and particularly scientists.

"The white sharks at a seal colony where we worked, they're working pretty hard, they're patrolling the colony, they're coming up to some pretty high speeds to catch the seals.

"We found that if you use the same amount as what they suggested, a 30-kilogram meal, then these animals will have to feed every 10 or so days so a lot more regularly.

"Their metabolic rate or the engine that runs them is much faster than what we had assumed.

"These animals are probably going to be feeding you know every few days, rather than multiple weeks."

Dr Semmens says the research also aimed to improve understanding of how sharks interact with the ocean ecosystem.

"We don't have a good handle on the population sizes of white sharks. We know that sharks in general are under pressure around the world from overfishing," he said.

"They're quite vulnerable because of their life history, they're long-lived, they reproduce late in their life and they produce a small number of offspring."

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