Only persons have legal standing to file suit.
I am not able to find binding US Federal precedent where a wolf was deemed a non-person, but in general, person is defined as either a natural person (human) or a statutory person such as a corporation, LLC, or trust.
If you know a Gray Wolf who wants to sue, then sure, go ahead and tell them to file their case and appear in court. Report back to us what the judge felt about it and whether Animal Control officers shot the litigant or simply took them to the pound.
