You never know how much help controlling rodents you are getting from snakes. It's never good to eliminate natural predators from an enviorment. Look what happend with the rabbits in australia. I can tell you that we do not have a rodent problem at our place. We have barn owls, and we welcome snakes into our yard. It may help you to know that annually, poisonous snakes kill only 1-5 people on average. That is a very slight risk. Think of how much more likely you are to be killed by honeybees, cars, other people, illness. The flu is more dangerous!