Riley's grown contentious since I left

Since I moved out, to go to college, Riley cat has been picking on the dog more than usual. They typically play-fight once a day; but since I've left, my parents have noticed (to their annoyance) that Riley and the dog have been going at it several times a day. Has anyone else experienced this with their cats? Is there anything we should do to meet Riley's needs, so that he won't vent his frustrations on the dog?

He is probably stressed with the change. You can get some Feliway to help calm him as he adjusts. Its called Comfort Zone on Dr Foasters and Smith web site.