An American crocodile (Crocodylus acutus) resting on a bed of seagrass. These medium-sized crocodiles are most commonly found in mangrove-lined estuaries and saltwater lagoons between the southern coast of the United States and the northern coasts of South America and Mexico. They are considered "Vulnerable" by the IUCN Red List, having undergone a population decline of 30% over the last three generations because of hunting for their hides and habitat loss. However, when their habitat is protected, their populations can recover. See a slideshow of more backboned species threatened with extinction.