Wolf hair brushes do not exist. The legend comes from an unthinking translation of the real name: "langhao", which calls a wild weasel from Siberia. Its tail hair are yellow, terse and sharp but never very long so there are no large brushes in this material, and they don't keep large amounts of ink. Anyway that's the best tool for awkward beginners in calligraphy and there is nothing better for traditional drawaing and painting (sumi-e). Because of this hair high prices, Japanese brush makers mix them with horse mane or preferably use badger ("tanuki").