大象传媒

Each female spotted hyena has only two or three cubs. Foraging takes mothers away from home so much that if they had larger litters they probably wouldn't be able to produce enough milk to quench the thirst of all the cubs. In addition, there is a strict pecking order and the daughters of high-ranking mothers also inherit high status. In fact, the pressure to dominate is so great that female cubs are awash with male hormones, and the masculinsing effects are astonishing. To all intents and purposes, the females have a complete set of male genitals. Even newborn female cubs are awash with high levels of male hormones with the result that they, quite literally, come out fighting. On top of this - and unique among mammals - baby spotted hyenas are born with lethal canine fangs. So the hormones which give the female her high rank also gives her some difficult children. Even while the mother licks the membrance from her third pup, the first two are already hard at work trying to murder each other. That is, until they realise that there is a more defenceless target available: the pup still in its membrane. This extraordinary behaviour is unique among mammals and has never been filmed before. Indeed, this cradle violence is so fierce that a quarter of all cubs are killed by their siblings and the worst fighting is between twins of the same sex. In adult life these twins are destined to be life-long rivals so getting rid of a competitor at the outset gives the winner a fantastic advantage. Outside the den, the mother may face a three-month struggle to keep the peace as the cubs continue to fight. But there's a fundamental conflict of interest between a mother and her cubs. Her aim is to rear as many healthy offspring as possible. But each cub gives top priority to its own selfish interests.