our cats started fighting

Question
We have had a male cat since 1995 (from pound, neutered and all 4 claws removed by prior owner). His ten-year male companions died in Sep 2005; we picked up a female cat (1-2 yrs old) in Dec 2005 from same pound. Both are indoor cats, we take them outside supervised. After introduction issues, they got along fine for eighteen months. They then started fighting, often touched off if the male noticed other cats wandering through our yard, but they continued to fight for days. We've been using pheromones at the suggestion of our vet (who checked the male), and that helped considerably, but two days ago they began fighting again, for no reason. They can walk up to each other, sniffing and grooming each other, but two minutes later be tearing out fur and caterwauling with no obvious provocation. What can we do to resolve this issue?

Answer
Glen,

Given that the vet has examined the male cat and found no obvious health issues it is a good idea to check the female cat as well just to rule out any possible health issues that can cause aggression. Given that this situation is fairly new you have a few choices. You can ask your vet for a referral to an animal behaviorist who can help you to find the cause of the aggression and help you and the cats to work through it. I can suggest a homeopathic remedy called Bac's Rescue Remedy which is a blend of flower essences to help calm and reassure. You can generally find Rescue Remedy at health food/natural health stores. I would recommend that you keep the cats indoors as something in their outdoor environments may have contributed to this problem. A dosage of about 10 drops per day in fresh water each morning should help you to see a different side of your kitties. I strongly caution you not to try and get in the middle of two cats fighting as it is dangerous and can result in injury....If you need to break a fight up a plant mister with I do hope that you are able to find a solution for this aggression issue. If you have any further questions or concerns, please do not hesitate to contact me again.