Any time a dog's behavior or eating habits change for no reason that think you can explain, such as a new baby being brought into the home or you just bought a new dog, it's time to see the vet first. And be sure that he sees a small-dog vet who, besides a physical exam, including neuro and ortho, does bloodwork. Changes in behavior are often the only way we know our dog is having medical problems or pain since he can't tell us.
There could be other reasons for his change in behavior, of course, but first of all you have to be sure there is no medical problem such as pain, tumor, high white cell count, anemia, major organ dysfunction, etc.
__________________ 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 |