Hi! I have only one cat, Groucho, who is four years old and was adopted at seven weeks. He has been the king around here since the day we brought him home. There have been no problems with Groucho while we're gone. He sleeps, he plays, he sits in the window for hours at a time. Maybe it's his personality but Groucho seems to enjoy his alone time. Even when we're home he will often go into his pet carrier which is in a quiet, out of the way corner and always open. Cats seem to have this incredible ability to amuse themselves with the darndest things. They also are extremely territorial. Since your kitty is the only one, he most likely has staked a claim to your place as being his own. He may resent an "intruder" coming into HIS turf.