Not all mammals have to eat living animals and plants. Humans (mammals) in some circumstances like a coma might have a tube inserted through themselves so that they may receive nutrients and water. Technically, to eat something alive is eating a living "thing" as once you kill something, it is dead. Even plants are pulled out of their roots thus considered dead. Therefore (in a way), mammals do not eat living "things". -S. R. Wahs. 04. 04. 2013.