For years, researchers have tagged sharks in the world's oceans to learn where they go, how they migrate and where they feed. While these tags have given us a wealth of data about their lives, many questions still remain. One of them is: why do some individuals travel vast distances while others stay closer to home? A new study published in the journal PLOS One may have the answer. It suggests that a shark's wanderlust may be due to the amount of energy stored in its body.