Proper (classic bimporph) werewolves can look fully like a human or fully like a wolf at will, only that light from the full moon powerfully switches them to the wolf shape. Despite the high expectations of some werewolves, even the best werewolf families give birth to yennorks, werewolves who are born locked in one shape (human or wolf) and cannot change form even at full moon. It has been speculated that such non-changing werewolves have gone marrying into human families or wolf clans and given rise to wolfmen of various descriptions and generally more monstrous shapes. The more traditional werewolf families like to kill their yennork children when they are still young. Another form of werewolf has a wolf as its "basic" form, and changes to a human at the full moon.
Werewolves can switch between human and wolf shapes at will, and each shape offers certain advantages. The human shape gives opposable thumbs, better eyesight, and a brain more suitable for rationalized thinking. The wolf shape gives claws, extremely good sense of smell that maps onto the mind the way that humans perceive different colored lights, and unthinking animal reaction times that might be critical for combat survival. Werewolves are cunning and can do a good deal of rational thinking even in wolf form; however, a werewolf that spends too much time in wolf shape may become more simple-minded and less able to live in the world of human intrigues. Baron Guye von Überwald (a.k.a. Ruston), who appears in The Fifth Elephant is an example of this phenomenon.
Werewolves can be severely wounded, but only fire or silver can cause lasting damage leading to death. In this sense, werewolves are undead although some would debate that werewolves haven't actually died at all and therefore cannot count as undead (Then again, they're large, scary, come from Uberwald and don't die when you stick a sword in them. What else do you want?). A silver collar was used to trap Angua von Überwald in Jingo: this had the effect of trapping her in wolf form and making it impossible for her to change back to Human. In order to dispatch a rogue werewolf, Samuel Vimes used a signal rocket, effectively a large firework, knowing the canine instinct cannot resist chasing and catching however intelligent the mind otherwise is.
Like the vampires, werewolves are hard to kill, physically powerful, and have become feudal rulers in Überwald. As is feudal tradition, werewolf noble families and vampire feudal families all feud against each other. Nevertheless, it is more common for a werewolf noble family to actually be a large clan with many members (see vampires for comparison). Much of this feuding, Pratchett develops out of two major sources: 1) a modern resurgence of werewolf-vampire animosity and 2) old eastern European traditions in which every vampire has a werewolf that hunts it in order to return the vampire to its grave. An additional layer comes into play when prey comes into the picture since both werewolves and vampires, at least until the Century of the Fruitbat, prey upon humans. Thus competition for resources creates a solid, biological, reason for animosity between the two species.
There is an old tradition called Game in which a pack of werewolves go in their wolf shape to hunt down a human running in a forest. This is by proper arrangement with the human, there are many rules including allowing the human a head-start. The rules dictate that if the human outruns the pack in a set amount of time, he is given a sum of money and treated to dinner at the werewolves' castle (instead of being their dinner). After much cheating by modern werewolves from a certain pack (see The Fifth Elephant), it is unclear whether such games are still run and, if they are, whether the old rules are obeyed. The game used to be healthy exercise for the werewolves and a fair chance at a large sum of money for the human.
Werewolves are not the only werecreatures on the Disc, apparently. As well as the well-documented ability of Vampires to turn into bats at will - in itself a were-ability - The Celebrated Discworld Almanak reveals that there is an Überwaldean legend of were-ducks. Whether this is a product of the sort of imaginative minds who write the Almanac or if it has any bearing in reality is a different question.
Known Werewolves, Major
- Angua von Überwald - a.k.a. Delphine, Sergeant in the Ankh-Morpork Watch
- Guye von Überwald - a.k.a. Ruston or the Baron, Angua's father
- Serafine von Überwald - Angua's mother
- Wolfgang von Überwald - Angua's brother
- Lupine - a werewolf with an interesting twist
- Ludmilla Cake - a werewolf who helps Lupine resolve a few of his issues
Known Werewolves, Minor
- Andrei von Überwald - Angua's brother, wolf yennork
- Elsa von Überwald - Angua's sister, human yennork, deceased (killed by Wolfgang)
- Hilda, Aunt - Angua's aunt, part of Wolfgang's pack
- Nancy - unknown relation, part of Wolfgang's pack
- Ulf, Uncle - Angua's uncle, part of Wolfgang's pack
- Unity - unknown relation, part of Wolfgang's pack
- Reaper Man - appearance of Lupine & Ludmilla Cake
- Men at Arms - first appearance of, then, Constable Angua
- Jingo - more of Constable Angua
- Feet of Clay- more of constable Angua
- The Fifth Elephant - Sergeant Angua and the first appearance of her family
- Thud! - another major appearance for Sergeant Angua
- Marie de France, "Bisclavret" (12th century lai) - one of the earliest "off-stage" shape-changes for werewolves
- Petronius, Satyricon - one of the earliest literary werewolves, a soldier removing his clothes to change form in a graveyard
- Gerald of Wales, The History and Topography of Ireland - involves two werewolves from Ossory, alluded to by Constable Visit in The Fifth Elephant.