In any
ecosystem, a top
predator is an animal that is not
hunted by any others. There need not be only one top predator in a given system, the typical
American farm can claim
owls,
cats,
hawks, and
humans as top predators.
Top predators are usually the animals most effected by pollution, as toxins become more concentrated in animals that eat other tainted creatures. This is why eagles and other birds laid softened eggs, back when DDT was in use. It's also a good argument against cannibalism.