Any time a dog's behavior changes, a full vet work-up is in order. He could be in pain or ill/injured, trying to protect himself.
If he's not ill or hurt, his behavior sounds territorial and protective, usually due to lack of boundaries or adequate leadership.
How long does he spend closed in his cage each day and what is his life like otherwise?
Who feeds and grooms, walks and trains him, gives him challenges and puzzles to solve?
If you can provide some more information about his age, weight, neuter status, health, activities, his crate time, daily life, etc, it will make evaluating what's going on with him easier.
__________________  Jeanie and Tibbe One must do the best one can. You may get some marks for a very imperfect answer: you will certainly get none for leaving the question alone. C. S. Lewis |