how long between owner leaving and you arriving?
Is he walked before owner goes to work?
how long has owner had him?
Does he do it when she goes out without him at weekends? or is it just during the week? Because it could be seperation anxiety or just pure boredom
They could try getting an old cardboard box, balling up newspapers and hiding treats in it, leaves a big mess.
Piggy ears to chew on, stuffed kongs.