Many biologists view predator-prey relations as natures version of an arms race, meaning that the physical and genetic changes that both predators and prey undergo are for bettering their abilities to outdo one another and survive. At any given snapshot in time either the predator species or the prey species will have more "technology" under their belt in terms of survival. For wildlife prey we see speed, poisons, coloration, armor, alertness, and deceptions pitted against a variety of such traits in the predator as well. An understanding of predation is important because the public is vocal and curious about what happens to predators and prey, but for wildlife managers its an understanding of predations role in populations dynamics that is key. Some of the most controversial issues in wildlife and conservation biology hinge on the extent to which predators affect prey numbers and visa verse. When predators and prey have evolved together, they interact on more equal footing. So the easiet and at times the most complicated of questions on this topic is...does predation affect prey numbers?
The best short answer for that is... sometimes. I know I know... what good is that answer! But the simple truth is that there is a balancing act going on at all times between predator numbers and prey numbers. We don't have to look very far to see examples of predators limiting prey population size (sometimes even to extinction). But for the most part, predation usually causes oscillations in prey abundance ranging from very high numbers to low numbers and everything in between. Some prey species persist and even flourish in numbers with predators in their midst. What we have to keep in mind is that prey are active participants in the life and deth process, always evolving and behaving in ways to reduces their chances of being killed. The best generalization that can be made on population responce is that predation can certainly regulate and help limit numbers of prey, but its unlikely to drive prey populations to extinction unless introduced species are involved or the prey population is small and fragmented to begin with.