Why did the dog react the way he did?

The date is August 4, 2026. The house is technologically advanced to the point that almost everything is automated. The house continues to function according to all of its programming even though the entire family has died. Given the evidence of their silhouettes outside the house and the "radioactive glow," there has been an atomic explosion. So, the family and everyone in the city has been killed. If this had been part of a larger...

The date is August 4, 2026. The house is technologically advanced to the point that almost everything is automated. The house continues to function according to all of its programming even though the entire family has died. Given the evidence of their silhouettes outside the house and the "radioactive glow," there has been an atomic explosion. So, the family and everyone in the city has been killed. If this had been part of a larger bombing and/or atomic war, more people are probably gone as well. Somehow, the dog has survived the blast. 

The dog comes into the house looking for its human family and hears only silence. The dog might have suffered radiation poisoning from the nuclear blast and this could have lead to his death or at least contributed to the sores or even affected its appetite. But given the physical description and the fact that the dog was kept outside the kitchen door, it is more likely that starvation was the cause of death: 

The dog, once large and fleshy, but now gone to bone and covered with sores, moved in and through the house, tracking mud. 

It sniffed the air and scratched the kitchen door. Behind the door, the stove was making pancakes which filled the house with a rich odor and the scent of maple syrup. The dog frothed at the mouth, lying at the door, sniffing, its eyes turned to fire. It ran wildly in circles, biting at its tail, spun in a frenzy, and died. 

The once large dog is now skin and bones. Having been deprived of food for an inordinate amount of time, the dog is close to death. With its little remaining strength, the dog froths/salivates at the smell of food from the kitchen, desperately runs around out of frustration, and finally dies of malnutrition.