[Free Registration/Login may be required to access all resource tools.] What is a mammal? They walk, run, swim, and fly. They live in the ocean, fly in the sky, walk on the prairies, and run in the savanna. There is a tremendous amount of diversity within the group in terms of reproduction, habitat, and adaptation for living in those different habitats. Learn more about mammal characteristics in this learning module produced by CK-12.