Virtually all forms of animal life from single-cell protozoans to insects, birds, fish, and mammals, including man, are either predator or prey, or both. A predator is any animal that feeds on other creatures. Prey, of course, are the animals used as food. At first, predation appears destructive and cruel because it involves the taking of life. Actually it's a beneficial process that keeps populations in check and contributes to the intricate balance of nature.
All animals have the potential to reproduce until they deplete their food resources.
When this happens, the animals die of starvation and disease. Sometimes this process can modify the habitat so that it becomes unsuitable for other species. One way nature protects against this is by predation. Predators take the old, sick, or unwary, thinning out the weak and assuring survival of the strong, healthy animals. Through millions of years of interaction, predators have adapted to catch prey, and prey have adapted to escape.