As Taran said, it's down to your table, but my take is this:
Shapeshift into a mundane animal (even if several pounds heavier than any living mundane animal) and you're in the clear. Damage caused is still mundane, since you had to learn how to do it.
Shapeshift using some variation on the Hexenwulf, and you're in a gray area, but zealous Wardens will likely see Black. Damage caused is mundane, but backed and supported by magic.
Shapeshift using some willing variation on the Loup Garou and you're solidly in the black. You've got a demonic co-pilot whom you've willing invited in, and you've surrendered control to it willingly. Damage is caused by magic, and is in no wise 'mundane'.