If you grew up with a brother or sister, you probably know what sibling rivalry is like. For a spotted hyena though, sibling rivalry is a matter of life and death. Spotted hyena mothers usually have twins. They give birth in a private burrow where the newborns live for the first few weeks of life. By the time the mother moves her offspring from the natal burrow to the community den however, there’s a fifty-fifty chance that one of her infants will be dead. What’s more, her children always emerge from their nursery covered with wounds. A look inside the burrow reveals what’s going on. After a long gestation cycle, newborn hyenas are remarkably well developed. Like Red Riding Hood’s wolf, they have big, open eyes and full sets of teeth. They won’t hunt for many months to come, so what are these adaptations for?