We are having a barking problem with our 7 month old puppy. He doesn't bark when we are home (very rarely), but everytime he is left home alone he will bark anywhere from 15 minutes to 2 hours straight. We live in an apartment so our next door neighbors have been letting us know if he barks and how long. Obviously we need to stop this behavior but we have yet to figure out how? As of now we are simply leaving an extra set of keys next door so they can come tell the dog to quiet down if he gets too bad. He is potty trained so he is has the run of the apartment while we are gone, although it is pretty small anyways. We are going to try kenneling him again whenever we leave and see if that causes him to stop barking. Although eventually we hope that he will be quiet without having to be kenneled. Does anyone have any suggestions for how to train him to not bark when he is home alone?