Footage of great white sharks often shows them ravenously feeding on marine mammals, and now a new study reveals that such feasts often occur after the sharks go on long journeys.
The study, published in the latest issue of Proceedings of the Royal Society B, reveals how important protection of established shark feeding grounds are, since so much concentrated feasting takes place at these sites.
“We know from researchers observing white sharks feeding on whale carcasses that one shark can eat more than 30 kg (66 pounds) of blubber in a single feeding,” lead author Gen Del Raye told Discovery News. “This has been estimated to be sufficient energy to allow a shark to survive for 1.5 months.”
“We also know that the sharks feed fairly frequently on juvenile northern elephant seals at certain seasons,” added Del Raye, who is a researcher at Stanford University’s Hopkins Marine Station and the University of Hawaii. “One of my co-authors, Salvador Jorgensen, for example, has identified the same shark feeding on 3 juvenile elephant seals in the course of one week.”
Del Raye, Jorgensen and their colleagues assessed great white shark fat stores over long periods by examining depth records from pop-up satellite tags affixed to sharks in the Eastern Pacific Ocean. Changes in shark buoyancy served as a proxy for how much weight the toothy predators were packing.
As a shark’s single largest organ, the liver, can account for 28 percent of an adult’s body weight. Other fat is stored in the shark’s muscles. While sharks fill up on fatty food after long journeys, no shark has ever been classified as obese. Their lifestyle is probably inherently too active for them to keep the pounds on.
Great white sharks go on long distance migrations covering over approximately 2,485 miles per trip. It's not certain why they undertake such lengthy journeys, it's likely foraging, mating or both.