Great White Sharks Eat More Than We Thought

The great white shark,Carcharodon carcharias, needs to eat several times more food than scientists had previously believed, according to a new calculation published Monday in the open access journal Scientific Reports. So if you had the idea that shark attacks are on the rise, maybe the big boys are just feeding their supersized appetites.

Jayson Semmens headed up a team of Australian and British researchers who observed that the notorious great white is a fierce predator that travels the world’s oceans, making it difficult and dangerous for scientists to study how often and how much food it really eats.

A previous calculation, done on only one individual, estimated that a 943 kilogram great white shark could survive on a mere 30 kilograms of blubber from marine mammals like seals for 1-1/2 months — “a widely cited figure that has perpetuated the assumption that large sharks only need to feed every few weeks.” The team was understandably skeptical of such a strong claim on the basis of one animal in one study.

To discover the true metabolic rate, the team looked at the energy burned by swimming. After examining almost 10,000 swim speeds, the researchers concluded that the predators demanded far more calories than the earlier estimate. Thirty kilograms of blubber would last less than 12 days, not even two weeks, let alone the six weeks suggested by the earlier research. That means that the great white shark probably eats three to four times as often as most people think.

Despite the great white shark’s enduring popularity in popular culture, including the Discovery Channel’s Shark Week and the iconic movie Jaws, the International Union for the Conservation of Nature (IUCN) has noted that science really knows very little about its biology. The IUCN has rated it as a vulnerable species because of threats like commercial or sports hunts and even media-fueled campaigns to kill the animals after a hungry shark bites.

Semmens and his colleagues feel confident that the new calculations provide a more realistic picture of how much great white sharks really consume. Pound for pound, the new estimate is comparable to how much we know that a mako shark must eat.

Is anyone really surprised by the finding that the species eats more often than once every six weeks? Or did you always suspect that the great white shark really knows how to chow down?

[great white shark photo courtesy Michael Fontenot, Flickr, and Creative Commons]