In folklore, a werewolf or occasionally lycanthrope is a human with the ability to shapeshift into a wolf (or, especially in modern film, a therianthropic hybrid wolf-like creature), either purposely or after being placed under a curse or affliction (often a bite or scratch from another werewolf) and especially on the night of a full moon. Early sources for belief in this ability or affliction, called lycanthropy, are Petronius (27–66) and Gervase of Tilbury (1150–1228).
The werewolf is a widespread concept in European folklore, existing in many variants, which are related by a common development of a Christian interpretation of underlying European folklore developed during the medieval period. From the early modern period, werewolf beliefs also spread to the New World with colonialism. Belief in werewolves developed in parallel to the belief in witches, in the course of the Late Middle Ages and the Early Modern period. Like the witchcraft trials as a whole, the trial of supposed werewolves emerged in what is now Switzerland (especially the Valais and Vaud) in the early 15th century and spread throughout Europe in the 16th, peaking in the 17th and subsiding by the 18th century.
The werewolf folklore found in Europe harks back to a common development during the Middle Ages, arising in the context of Christianisation, and the associated interpretation of pre-Christian mythology in Christian terms. Their underlying common origin can be traced back to Proto-Indo-European mythology, where lycanthropy is reconstructed as an aspect of the initiation of the warrior class. This is reflected in Iron Age Europe in the Tierkrieger depictions from the Germanic sphere, among others. The standard comparative overview of this aspect of Indo-European mythology is McCone (1987). Such transformations of “men into wolves” in pagan cult were associated with the devil from the early medieval perspective.
The concept of the werewolf in Western and Northern Europe is strongly influenced by the role of the wolf in Germanic paganism (e.g. the French loup-garou is ultimately a loan from the Germanic term), but there are related traditions in other parts of Europe which were not necessarily influenced by Germanic tradition, especially in Slavic Europe and the Balkans, and possibly in areas bordering the Indo-European sphere (the Caucasus) or where Indo-European cultures have been replaced by military conquest in the medieval era (Hungary, Anatolia).
Various methods for becoming a werewolf have been reported, one of the simplest being the removal of clothing and putting on a belt made of wolfskin, probably as a substitute for the assumption of an entire animal skin (which also is frequently described). In other cases, the body is rubbed with a magic salve. Drinking rainwater out of the footprint of the animal in question or from certain enchanted streams were also considered effectual modes of accomplishing metamorphosis. The 16th-century Swedish writer Olaus Magnus says that the Livonian werewolves were initiated by draining a cup of specially prepared beer and repeating a set formula. Ralston in his Songs of the Russian People gives the form of incantation still familiar in Russia. In Italy, France and Germany, it was said that a man or woman could turn into a werewolf if he or she, on a certain Wednesday or Friday, slept outside on a summer night with the full moon shining directly on his or her face.
In Hungarian folklore, the werewolves used to live especially in the region of Transdanubia, and it was thought that the ability to change into a wolf was obtained in the infant age, after the suffering of abuse by the parents or by a curse. At the age of seven the boy or the girl leaves the house and goes hunting by night and can change to person or wolf whenever he wants. The curse can also be obtained when in the adulthood the person passed three times through an arch made of a Birch with the help of a wild rose’s spine.
The werewolves were known to exterminate all kind of farm animals, especially sheep. The transformation usually occurred in the Winter solstice, Easter and full moon. Later in the 17th and 18th century, the trials in Hungary not only were conducted against witches, but against werewolves too, and many records exist creating connections between both kinds. Also the vampires and werewolves are closely related in Hungary, being both feared in the antiquity.
Most modern fiction describes werewolves as vulnerable to silver weapons and highly resistant to other injuries. This feature appears in German folklore of the 19th century. The claim that the Beast of Gévaudan, an 18th-century wolf or wolf-like creature, was shot by a silver bullet appears to have been introduced by novelists retelling the story from 1935 onwards and not in earlier versions. English Folk-lore, prior to 1865, showed shape shifters to be vulnerable to silver. “…till the publican shot a silver button over their heads when they were instantly transformed into two ill-favoured old ladies…” c. 1640 the city of Greifswald, Germany was infested by werewolves. “A clever lad suggested that they gather all their silver buttons, goblets, belt buckles, and so forth, and melt them down into bullets for their muskets and pistols. … this time they slaughtered the creatures and rid Greifswald of the lycanthropes.”