I have a problem with my 8 (soon 9) year old Labrador. At night, he runs away and always comes back really tired, but keeps going outside every night. From time to time, he howls outside the house (alone). He is never hungry, thirsty, has a lots of space around the house, but keeps doing this. I'm not really superstitious, but this really creeps me off.
Why does he run away and howl outside?