I don't believe it! All these writeups and not a single mention of the full moon? Werewolves traditionally (in other words, in Discworld, all the films and other contemporary culture items) must convert to their wolf form at the full moon. Some have control over their form at other times, others must remain human for the rest of the month... but the full moon is the traditional time for hunting, as creatures are sleepy and dumb, and there is more light at this time than any other, as well as there being light for the whole night.