Originally Posted by
Tanya
And how did the trainer manage him when the trainer had to leave the house? It's sounding like this dog has never learned to regularly "be alone". and is now suddenly alone in the backyard for 8 hours. Or it may just be a dog being a dog.
Can your dad send him to like a doggy daycare? Or built a kennel if crate training/dog proof room isn't an option? There no "easy" solution here. Find a safer place to contain the dog while your dad is gone. Kennel, dog proof room, doggy daycare, dog sitter. Then when you get back, work on desensitization and maybe crate training or testing how he does in the home and work up from short times to longer times alone.
How much exercise (physical and mental) is the dog getting NOW vs when you are there? If you dad can't keep up maybe pay for a dog walker to come mid-day and help tire out the dog.