Great White Sharks Journey for Thousands of Miles on Liver Power

Great white sharks can journey for thousands of miles, crossing stretches of ocean during their hunt for food and mates. Now, scientists have learned a little bit more about how these massive creatures manage to travel so far non-stop; it's all about their livers.

Great white sharks aren't picky eaters, so you might assume at first that these creatures snack continuously while making their cross-ocean voyages. Yet it appears that this isn't the case. Instead, the predators store up fat and nutrients, rather like oceanic camels, before starting out on their 2,500-mile journey across the sea.

"We have a glimpse now of how white sharks come in from nutrient-poor areas offshore, feed where elephant seal populations are expanding--much like going to an Outback Steakhouse--and store the energy in their livers so they can move offshore again," said Barbara Block, a researcher at Stanford Woods Institute for the Environment, in a news release. "It helps us understand how important their near-shore habitats are as fueling stations for their entire life history."

Like polar bears, whales and seals, great white sharks store fat; they just happen to store it in their livers. In the latest study, the researchers looked at a well-fed juvenile shark at the Monterey Bay Aquarium, documenting a steady increase in buoyancy as the shark's body mass increased due to stored oils in its liver. The scientists then turned to the wild, examining detailed data records from electronically tagged great white sharks swimming in the eastern Pacific Ocean. By estimating the rate at which the sharks sank during drift dives, they were able to estimate the amount of oil in the animals' livers. In the end, the researchers found that over time, buoyancy steadily decreased. This means that the sharks weren't replenishing their fats and were, instead, subsisting on stored oils.

"Sharks face an interesting dilemma," said Sal Jorgensen, a research scientist at the Monterey Bay Aquarium, in a news release. "They carry a huge store of energy in the form of oil in their massive livers, but they also depend on that volume of oil for buoyancy. So if they draw on those reserves, they become heavier and heavier."

The findings reveal the importance of these coastal oases to great white sharks. If their food sources there are depleted, it's possible that these rare creatures could face even greater challenges than they already do. The research is crucial for conservation efforts and shows a little bit more about these large animals.

The findings are published in the journal Proceedings of the Royal Society B.