Bats are the only mammals that can fly, but Vampire Bats are the only known Mammals that survive solely on blood. If a Vampire Bat doesn’t find blood for two nights, it will die. Well-fed bats share blood with others in exchange for grooming. After a baby is born, other bats feed the mother for about two weeks. These bats feed on blood from sleeping cows, pigs, horses and birds. They don’t drink enough blood to harm the animal, but their bites can cause nasty infections and disease.