We have 5 cats that have lived with each other for quite some time now. Most are siblings, though not all from the same litter, and have always gotten along just fine. The 3 males were fixed a while back, and we just got the 2 females fixed yesterday. Today everyone is on edge, hissing, growling, and even attacking each other. We have also had a few cases of spraying today, a problem we never ever had before. Most of the fights seem to be started by one of the females, though not all. Is this a reaction to the surgery, where the female feels she is injured and is putting up a strong front to get the rest away from her? At first this is what I was thinking, however when one of the cats meows, the more aggressive female searches them out looking for a fight. Any ideas?