Dog's Inner Fears?

Last night, the middle of the night, there was a rattling and banging, loud enough to wake us both up. My first thought was raccoons of course, as I had run one off the night before. The sound seemed to be coming from the living room where Bud sleeps. He has a comfy kennel cage with a blanket draped over it and a heat lamp on chilly days to ease his old doggy bones. Bud's a good sleeper. That is, he does a lot of it. He racks up about 18 hours a day, and as he's quite deaf, sleeps through most night sounds.

The noise was coming from Bud thrashing and banging the cage around quite violently, When I saw him I thought he was having a seizure or something because even when I laid my hands on him he continued his thrashing and twisting. Eventually he stopped and woke up, apparently quite shaken and was very clingy for a while, then started running around in his excited circles. I let him outside to run it off. It was cold, so he was back in the kennel in short order, curled up like a happy little puppy falling asleep.

I know dogs dream. I call them rabbit dreams. Bud's legs kick in running twitches, sometimes softly boofing in his sleep. I like to imagine in his sleep he's a wolf again, running in a pack, bringing down caribou, bringing down the big game and tearing it apart with his packmates. More likely he's reliving chasing a cottontail the day before. Who knows. I think last night was different, it was a dog nightmare, canine night terrors. What awful thing could a Pug imagine in his deepest sleep? They don't seem to have a concept of death, though when Sam died, the separation was traumatic for Bud. Pugs have been bred to be perennial puppies. What are Pugs afraid of deep down in their bones?  I hope he sleeps better tonight. Poor little pup.