Dark creatures are frequently mentioned in the Harry Potter books though the term is not easily defined. The Harry Potter Lexicon speculates in its essay on the subject that dark creatures, as opposed to normal magical animals, are those that use dark powers for more than mere survival. Many magical creatures, such as manticores and erklings, are very dangerous, but are not considered "dark creatures," since they are natural predators utilising their power in their quest for food, reproduction, and survival; having no consciences or malicious purposes, they may not necessarily be considered "evil." A dark creature, on the other hand, seeks to harm for the sake of harm, not for its own survival. Many such creatures are defined in Fantastic Beasts and Where to Find Them. It is possible (though this is not clear) that the term demon is an appropriate term for any Dark creature, since some such creatures, such as Red Caps and grindylows, are known to be both. Dark creatures do not necessarily reproduce and may simply result from spontaneously generating in places of strong ambient Dark Magic or where a strongly emotive or suggestive act has been committed. Red caps, for instance, appear on battlefields or other locations where human blood has been spilled in large amounts. Dementors "grow like fungus," according to J. K. Rowling, in the foulest, darkest places. Most dark creatures are not, by human standards, intelligent; vampires and werewolves, who are intelligent, are part human.