Some flagship species are keystone species, like the African lion, a top predator: it used to control the populations of large herbivores, protecting ecosystems across the entire landscape. However, the lion's ability to serve as a keystone species is decreasing as its population and range decline. The WWF uses flagship species as one of its species classification categories, along with keystone and indicator species. It chooses between these when selecting a priority species to represent the conservation threats facing a certain region.