Two cats who do not get along at all

Question
I adopted a young female cat 4 months ago and brought her home where I already have a female cat I'd adopted 6 years ago.  I followed instructions on introducing them very gradually; however, to this day they hate each other. The older cat attacks/chases the younger back into one room when she catches her out of it.  The younger is larger.  I have two unhappy cats and one unhappy adoptive Mom. Can you help?

Answer
Janet,

It sounds to me like you started off by doing the right thing, sometimes the first stage of new cat introductions (isolating the new cat behind a closed door) isn't long enough. I generally recommend that pet parents isolate new cats/kittens coming into their home for a minimum of 2-3 weeks. Obviously it isn't fair after 4 months to go back to stage one. I'm wondering if the aggression has anything to do with hormones - if the cats aren't sterilized they're more likely to react more territorially which means more fighting. I'm also wondering if you've had any changes in your household from prior to adopting the new cat - this could help to explain why the new cat simply didn't seem receptive to a feline companion. If you've renovated, had a baby, gotten divorced, gained or lost a family member, etc these changes can affect a cat pretty profoundly because cats are fairly territorial and they aren't big on change. You could certainly try a homeopathic remedy called Bach's Rescue Remedy which is a blend of flower essences designed to calm and reassure. This is a safe remedy and you can't go wrong with it. I'd recommend adding 7-9 drops of Rescue Remedy to fresh bowls of water each morning, you may notice a fairly dramatic settling down in one or both cats if the issue has to do with trauma or anxiety. Whatever the underlying issue is I'm confident that it can be worked with provided you have an experienced and competent holistic veterinarian and possibly a behaviorist. A holistic vet is trained in conventional medicine as well as one or more alternative therapies such as homeopathy, massage or acupuncture. Holistic therapies tend to be quite effective in cats when properly applied and a vet open to alternative therapies may be able to offer you options that conventional medicine just doesn't offer with fairly good results. I suspect that the issue in this household is one of dominance where the older cat is merely asserting dominance over the younger cat and unfortunately the conflict comes about when the younger cat just doesn't want to be pushed around anymore. Unfortunately I can't say for sure that this is the case because I haven't seen your cats in action, how they relate to each other and the humans in the home. I really think that it would be best to seek the advice of a holistic vet and get a referral to an animal behaviorist specializing in cat behavior, this way non-pharmaceutical options can be tried and the behaviorist can give you a more accurate idea of what's going on as s/he can see for him/herself the body language, triggers, responses, etc.