We took in a four year old sheltie about a month ago. She seems to have learned where to go outside and even has her own "spot" on the deck. We can leave her in the house and go out for several hours and there are no accidents. However, when we go upstairs at night to sleep (she doesn't want to go up the stairs) she will always urinate in one spot right in front of the door that we open to let her out during the day. She will do this several times overnight, even after doing her business right before bedtime. What could be the reason for this? What could we do about it? I doubt you could call it separation anxiety since she is fine when we are not home. Thank you for any help! We never owned a sheltie before (only collies) and just want to get the opinions of more experienced owners.