a lot of times a dog will do this to hide the scent of a female either coming into heat or already in heat.I have 3 male dogs and 1 female.After the female does her bussiness all three boys will go behind her and either lick up or pee on her pee spot.Believe it or not but this is normal behavor.I hope this eases your mind and you don't think you have a kinky dog!