Do you confuse who and that in writing? Don't feel bad if you do. Most people struggle with this one because it's so common in speech to use "that" instead of "who".
Just remember, when referring to a person, you use "who". When referring to an object or another type of noun, use "that", like in the examples above.
That said, sometimes it's appropriate to use "who" instead of "that" when referring to animals and other sentient beings, especially if you're trying to humanize them. If the wolf in your book, for instance, is a shapeshifter or has a strong bond with a character (or human mannerisms or speech, etc), try "who" instead of "that" to further humanize him or her.