Cubs fight viciously, often quite literally from the moment they're born. BBC's Carnivore! series has gruesome footage illustrating this. A hyena has given birth to three cubs, and two are already fighting savagely – until they notice the third, still being licked dry, and attack it. As many as 25 percent of all cubs may die from such fights before adulthood. The worst fighting is between two sisters in the same litter. As soon as she can, the stronger female will kill the weaker. Unlike most carnivores, hyenas are born with their eyes open and teeth functional.

Q: Doesn't the mother stop this?
A: Occasionally she tries, but it's a losing battle. Also, cubs dig a network of smaller tunnels from the birthing den, tunnels into which the adults don't fit, and will kill each other there. Or, the weaker cub may be so intimidated that it doesn't dare come out to nurse and so starves to death.