I have two cats - our male is just over a year and our female is 8 months old. Both of them are fixed, and both use the litterbox with no problems during the week while we are home. However, if we go away for a weekend (of course leaving them lots of food and water!), we come home and there is usually a "present" or two waiting for us on the carpet! This has just started recently and I have no idea what to do about it! Are they mad at us for leaving for a few days? How can I correct this behaviour! HELP!