Protecting keystone species is a priority for conservationists. Unfortunately, the keystone functions of a species may not be known until it has been extirpated and the ecosystem changes. Keystone species may occur at any level of the ecosystem, from plants and herbivores (plant eaters), to carnivores (meat eaters), and detritivores (waste eaters). Examples of keystone species may be top carnivores that keep prey in check, large herbivores that shape the habitat in which other species live, important plants that support particular insect species that are food for birds, bats that disperse the seeds of plants and many other types of organisms.