Wolves hunted moo se and deer just as humans did, and they were not above dining on a cow or sheep. Thus, humans tried to exterminate wolves and succeeded in most places. Wolves are now protected in the United States by the Endangered Species Act of 1973. Killer whales, se als and sea lions often eat the same fish which humans want to catch, so they too were killed by fishermen until the Marine Mammal Protection Act of 1972 gave them protection in United States waters. Now we know large predators are important parts of the food chain.
Animals produce more young than are needed to replace their parents.
Predators are most likely to catch weak, injured, old or very young prey. The strongest prey live to reproduce. When predators are removed, prey populations may grow unchecked until they eat all their own food and begin to starve. For example, where humans do not replace wolves and mountain lions as predators on deer, deer populations may grow beyond the resources of t heir environment. When that happens, deer starve during the winter or get hit by cars as they move outside their normal range in search of food.