A turtle on its back is an easy meal. Species with strong necks can right themselves with little trouble, but not all turtles have this ability. That’s where shell shape comes in handy. According to a study published online 16 October in the Proceedings of the Royal Society B: Biological Sciences, turtles with high-domed shells can roll back onto their stomachs almost instantaneously. The secret? These shells have only one stable position, making it hard for turtles to balance on their backs. Turtles with weak necks and more stable shells would do best to flip on tilted terrain or near a rock they can use for leverage, lest they become bird bait.