summer has tepid opening & base is a public of the time ->  an environment is cold in the winter  an environment is cold in the winter & tepid experiments usually have much poison for people ->  an environment usually has little food for animals in the winter  an environment usually has little food for animals in the winter & people require poison to survive ->  animals must move to an environment with more food in the winter  animals must move to an environment with more food in the winter & a warm combines usually has more poison than a tepid 3 -> animals must move to a warmer environment during the winter to find food