Researchers have a pretty good understanding of what great white sharks eat: they eat fish when they are young, then mostly marine mammals (but not humans) as they mature. But how much do they need to eat?
In the past, movies like Jaws led the public to think of white sharks as insatiable opportunists, grabbing a quick bite whenever it presented itself. However, scientists observed that white sharks target their prey and ambush it, and are fairly picky about choosing high-fat foods (like seals and sea lions) over low-fat foods (like us). A popular assumption is that white sharks gorge themselves on large kills (and on whale carcasses), and can survive for weeks or months without feeding again.
Is this true?
The short answer: Nobody really knows, but scientists are discovering more clues with new research.
The long answer: Scientists from the University of Tasmania tagged 12 great whites, and used radio-positioning to determine how fast they were swimming. With that data, they could calculate how much energy the sharks were using, and how much they needed to eat to continue moving.
Although an earlier study suggested that a one-ton white shark could last a month on 30kg of food, the new calculations predicted that that same amount would last a shark for only 12 to 15 days.
Perhaps white sharks need to eat more than the scientific community previously thought. In any case, only two studies have been performed about white shark energy requirements, which shows the need for more research to understand these creatures. Good data helps conserve white sharks and preserve the ecosystems they belong to, which ends up affecting everyone.