From feisty mongooses who start wars to pick the perfect partner, to swaggering peacocks faking a mating call and thieving macaques who kidnap babies to get ahead, the natural world appears to be rife with animal rogues. But what is driving them to these seemingly extreme acts? Liz sets out to reveal the fascinating science that lies behind these animal antics, meeting experts around the world who are making groundbreaking discoveries. In Tanzania, she finds that a bad case of sibling rivalry can actually benefit a whole hyena clan, and on the American plains she learns how promiscuity can be the key to having healthy prairie dog pups. When it comes to the mating game, it seems some animals are rewriting the rulebook with their outrageous behaviour. But as Liz discovers, it could also be the key to their survival.