This distinction is critical, as one crime victim in the state of Washington recently learned:
Police say a man was carrying a dead weasel when he burst into a Hoquiam apartment and assaulted a man.
The victim asked, "Why are you carrying a weasel?" Police said the attacker said, "It's not a weasel, it's a marten," then punched him in the nose and fled.
This incident makes more sense once you learn an important fact: the assailant was actually looking for his girlfriend at the time.
Link -via Lowering the Bar | Photo of an actual weasel by Flickr user Cecil Sanders used under Creative Commons license