Large carnivores, from lions to polar bears, are among the most iconic and charismatic species on earth. They also play vital roles in many ecosystems, restricting populations of herbivores from reaching levels where they degrade vegetation and prevent woodlands and forests from regenerating. But the world's top carnivores are in big trouble, with over three-quarters in decline and more than half now present in less than half their historical ranges. This is the message from a review paper published in Science yesterday. And the paper comes just a few days after another study found that the genetically-unique West African lion is down to just 250 breeding adults.