Great whites: even hungrier than you thought

Perhaps not surprising to any who suffers from galeophobia, researchers now believe great white sharks eat far more than previously thought.

An Australian study published this week found that great white sharks, the world’s largest predatory fish, eat three to four times more food than once believed.

That’s considerably more than the findings of a 1982 US research team. Then, it was estimated that a meal of approximately 66 pounds of mammal blubber could sustain a 2,160-pound shark for approximately six weeks, according to the website Real Clear Science.

However, University of Tasmania researchers reported this week that 66 pounds of blubber was only enough to glut a great white for about two weeks, according to a study published in Scientific Reports on the nature.com website.

Researchers tagged a dozen great white sharks off the coast of the Neptune Islands off South Australia and calculated their metabolic rate derived from swimming speeds, according to Agence France-Presse.

They then worked out how much energy the sharks burned and how much food they required.

The amount of energy required by great white sharks was equivalent to eating a seal pup every three days, according to senior research scientist Jayson Semmens, the lead author on the study.

“Based on the past data, that rate would have only been one pup every 173 hours,” according to Real Clear Science. “So this means that cute, cuddly, furry seal pups may be getting horrifically consumed much more often.”

The Neptune Islands are off the coast of South Australia, shown in red.

Real Clear Science based its calculations on the needs of a 2,160-pound great white.

“And keep in mind that some great white sharks can grow to be nearly 5,000 pounds!” it added. They probably sport a more voracious appetite …”

Semmens told ABC television that the US researchers in 1982 were working with a single shark, and may well have inadvertently chosen a great white that “wasn’t working very hard” at the time of their study.

The results of that limited inquiry perpetuated assumptions that large sharks could survive long periods without eating.

By comparison, the great whites at the seal colony off the Australian coast were working hard to and reaching high speeds to catch seals, Semmens added.

“Their metabolic rate or the engine that runs them is much faster than what we had assumed,” he said. “These animals are probably going to be feeding you know every few days, rather than multiple weeks.”

The study also emphasized the great white’s role in the ocean ecosystem, according to Agence France-Presse.

“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,” Semmens 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.”

Semmens said the unintended consequences of overfishing great whites are far more important than realized.

“They’re keeping under control a lot more animals than we thought,” he said.