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Because lambs were eaten by coyotes, ranchers hunt and kill the coyotes. However, killing coyotes may upset nature's balance. Scientists have found a way to protect sheep without killing coyotes. Coyotes are fed lamb meat treated with a drug. When they eat the meat, they get sick. Now, coyotes won't go near lambs. They hunt rabbits instead. What is the main idea?
What is "how ranchers protect sheep and coyotes?"