Need help! Landlord Rights: Dog & Boat?

My parents are landlords and a recent tenant did not pay rent for over two months with excuse after excuse as to when he would just move out. He didn't have a lease and was only there for three months. He finally said he would be out by this past Saturday. (We found this out on the same day, Saturday) The house has been emptied with the exception of a boat in the front yard & a dog in the back. A few friends of the ex-tenant came back on Sunday to clean the house and handed my parents the keys. On Monday, the boat is still in the yard and the dog was still locked in a cage. The dog is a mastiff and hadn't had water, food, or exercise since Saturday. Could be even longer as far as we know. My parents brought the dog home because it was grossly malnourished and was laying in its own feces for days. What are their rights at this point? The ex-tenant hasn't answered the phone regarding the dog or the boat since Saturday. Now.. on Tuesday he has his sister call to say both will be removed sometime tomorrow. What are my parents rights here. Can they just have the boat towed? Do we really have to give the dog back to someone who obviously doesn't take care of him. HELP!