Agree, it could definitely be shadows, or something you have overlooked. Or if you have moved an item into a different place and your pup didn't see you do it... (my dog will growl at a handbag on the table: she thinks it belongs on the door hook! I had to put up big thick curtains because the shadows of trees moving at night drove her barmy).
A dog also has a far better sense of hearing than we do (I think about 5x?) so it might be something high-pitched and far away, such as a car alarm.
If he really is in fact barking at nothing, it might be worth taking him to the vet for a quick look-over. If he has a blocked ear or something like that, it could cause a ringing sensation which would undoubtably make him upset.
Please let us know how you get on with this. |