Depends how you define greed. There are many examples of species that deploy strategies to satisfy their needs at the expense of other species. Never forget that the piurpose of every living thing is to provide the food of another living thing. Whether the predator kills its prey or waits for its prey to be killed or die from "natural causes". I use inverted commas here because I would argue that all causes of death, even being killed by another creature, are natural.