Yes, it's because of all those dog scents and he wants to mark his territory. Cute name, btw. Luke is 3yrs old and is house broken and never pees anywhere....except when I walk into PetsMart. What I would do is, before going in, make sure Batman pees outside and praise him. Then go in and watch your dog like a hawk. If he attempts to go, pull him away and say "no". This is what I do and Luke is fine. Good luck.