Behavior - Aggression between Cats


Behavior - Aggression Between Cats

Territoriality problems between cats

Question: Greetings Dr. Richards,

I am a subscriber to the Vetinfo digest and I have a question regarding my cats I wanted to ask you about. I have two 91/2 yr old female cats (had them since they were 4 wks old), both sisters, from the same litter (missy & sissy). Usually them get along great, play with each other & groom each other all the time. They are both indoor/outdoor. 3 days ago, missy was outside & I saw her come to the door & she could hardly walk/stand. She couldn't move her right hind leg. She had been walking a little funny on that leg for a couple of months. I had taken her to her Dr. then & it seemed everything was ok & I was to give her baby aspirin. I took her to the Dr. this time & they took X-rays & saw no broken bones/wounds but saw a small piece of bone floating in her knees & looked like she had arthritis & she must have injured/sprained her leg such that she couldn't use that leg. The Dr. prescribed some pain killers & antibiotics.

After I brought missy back from the vet's, sissy, her sister, refuses to recognize her & if she gets too close, she will threaten her. This is not the first time this has happened. 2 yrs ago, missy was in the hospital for 3 days due to chronic vomitting & after she got back, sissy would not recognize her & wouldn't come inside the house while missy was inside. It took her a long time (maybe 2 months) to come around to recognizing & accepting her. It seems to be happening again. Can you explain this behavior ? Is it because missy is sick that she emits a different/foreign smell which sissy doesn't recognize. Is there something one can do about this ? I will appreciate any thoughts/suggestions you might have. Thanks for your time & a great job you're doing on vetinfo.

Regards, Hemanshu

Answer: Hemanshu -

I am hopeful that Sissy is accepting Missy again by now. I think that this sort of behavior occurs in cats due to territoriality. It just doesn't seem to take much time at all for one cat to feel that it now owns the whole house and wants no intruders, even one that was formerly a housemate. I do not have a sure fire treatment for this condition. It sometimes helps to use Feliway (tm) spray in the house prior to bringing the cat home who has been gone for a while and then to use it for a couple of weeks afterwards.

It is a pheromone spray that is supposed to induce a friendly or calm feeling in cats. We have tried using anti-anxiety medications in this circumstance in a couple of cases, with variable luck. We have been using buspirone (Buspar Rx) but it sometimes makes cats more aggressive so it is a little bit of a risk to use this medication. Some vets like to use amitriptyline (Elavil Rx) or paroxetine (Paxil Rx) but we have not tried either of these medications so I can't give you a personal perspective on them.

It may help to keep the cats in separate areas of the house for the first few days and to switch the areas that they are in, so that each cat gets used to the other one's presence again gradually. This sometimes helps when introducing a new cat into the household.

Mike Richards, DVM 1/9/2002

Aggression between cats

Question: Dear Dr. Richards,

I have 2 housemate indoor cats in a tiny (700 sq ft) one bedroom condo. The male, Toby, is 10 yrs old, 18 lbs, a black & white Tuxedo cat; the female, Lily, just turned 4, weighs 7 lbs, and is an Abbysinian mix. They have been together for 3 years and usually get along O.K. Never really have been great buddies, however. Occasionally, Toby will approach Lily in a aggressive manner and she will back off and run away. She has a couple of good hiding places that Toby cannot get into because he is so big. She also will occasionally jump on Toby's back in a kind of playful manner, and is not usually frightened of him.

Toby's aggressive behavior has turned especially nasty and more or less constant since lst Friday, however. I had been in the hospital for major surgery for 3 nites just prior to this and a friend stayed with the cats. He has done this often in the past when I've had to travel on business for as much as 2 weeks, so this was really nothing unusual. Toby now chases Lily every time he comes across her and even stalks her if she is anywhere he can see her. Yesterday, he attacked her while she was in the litter box. (I have two boxes for them and they both use each freely). I had moved one of the boxes just before I went into the hospital so I could reach it more readily. Not sure if that was enough to cause this problem, but I moved it back where it was previously. They have still been eating side by side if I can get Lily to come out of where she is hiding. She is definitely frightened of him now. I asked my friend if something had happened to set this off while I was in the hospital, and he said nothing that he knew of.

There is no way to separate the cats in this condo which is really a glorified studio. I tried shutting Toby in the bathroom and he made such a ruckus banging and scratching at the door that I had to let him out or risk waking the entire building occupants up.

To add to this problem, we will be moving in about a month to the Big Island of Hawaii. It will be to a much larger house, about 1800 sq ft. But not as many hiding places. And I know the move will be traumatic in itself.

I have a homeopathic anxiety remedy, HomeoPet, which contains Cypripedium Pubescens 6c & 30c, Ignatia Amara 6C & 30C, Borax 6C & 30C, Nux Vomica 6C & 30C, Colchicum Autumnale 6C & 30C, Veratrum Album 6C & 30C, 20% alcohol USP in distilled water. Have been giving 3 drops 3 times/day to Lily as directed on the bottle -- thought is to calm her down so she is less frightened of Toby. It seems to set him off more if she appears scared. Is this anxiety remedy worthwhile? She seems a bit better today, and we have not had any attacks. I have been able to stave any off by speaking sternly to Toby and squirting him with water. But he still stares at Lily constantly with huge pupils when he is awake. And I cannot stay with them all the time.

Any thoughts from you will be appreciated. We are not sleeping well here. Cats are both due for annual check at vet in about 3 weeks. Should I move visit up? I really hesitate to use drugs -- would like natural remedy or behavior mod.

Thank you, Virginia

Answer: Virginia-

I don't think that it is likely that there is a physical cause for the behavior that you are seeing, so I suspect that moving up the vet office visit won't help, unless your vet has a special interest in behavioral problems.

I do not have faith in homeopathic medicine, but I do think that the products are safe if they are prepared properly for homeopathic use. So if you wish to try them and don't mind the expense there is no reason not to.

We have been having some luck, especially in situations like this, in which cats used to have a truce going, with the use of Feliway (tm). It is a synthetic pheromone manufactured to match the cheek pheromones of cats, which is their "friendly" pheromone. Spraying it around the house following the directions for urine spraying behavior (what it is approved to treat) seems to help calm down aggression between cats, too. This is not a proven use of this product and it is sort of expensive, too --- so that part of this advice matches the use of homeopathic products. It is safe but it there isn't any proof it will help, either.

You have some time to build a cat complex with a hiding spot small enough for Lily or just to build her a carpeted box with a small enough hole for her and not him, if it looks like nothing else is going to work.

Moving might actually help in a situation like this. It might makes things worse, too, but I like to be optimistic until reality forces me not to be. It might help to let Lily have first crack at roaming the house alone by keeping Toby in a cat carrier until she is very familiar with the house and its layout. That could give her an advantage if there is trouble and it might make it seem more like it is "her" house, which might slow Toby's aggression some.

It is a very good idea to ask your vet about this and it might be good to notify the receptionist, when you make the visit, that you have a behavioral question, in case they want to schedule a little extra time.

Mike Richards, DVM 9/13/2000

Aggression between cats

Question: Dear Dr. Mike: In June, I rescued a stray kitten, Bongo, (DSH), from the road side, and after he received his shots and was tested for the standard illnesses, we brought him home. We also have a 5 year old female DSH, Ty, who has never been very nice to anyone except me and my husband. We kept the 2 cats separated for 10 days and then introduced them. Since then, Ty has become aggressive toward me and my husband, and she despises the kitten, although she has never hurt him. Our home's floor plan will not permit us to "zone" the house - we would have to keep one of the cats shut up in a room to keep them separated.

Ty is depressed, non-responsive, ill as a hornet, etc... I've consulted with my vet and we've tried clomicalm and buspar, neither of which worked. It's difficult to give Ty medication because she won't allow us to touch her, and she never took pills easily.

I contacted a vet/behaviorist in North Carolina, but the earliest appointment she has is in November. I would like to find a vet/behaviorist in my state, South Carolina. Do you know of anyone in SC (my vet doesn't) and I cannot find a website with this information. I am in dire need. If I can't find a vet/behaviorist, would a non-vet behaviorist be a wise alternative? I love both my cats, but I cannot stand seeing Ty so unhappy much longer. Thanks for your input. Best, Wyn

Answer: Wyn-

I do not know of a behaviorist in South Carolina, either. There is a behavioral consultation service from Tufts University online, though. It might be worth checking into it. The link is:

I think that there is a behaviorist at the University of Georgia veterinary school, too, just in case that would help.

Buspirone has been the best medication for us when dealing with aggression between cats and it has not worked in many cases. We have recently been using Feliway (tm) for situations of aggression between cats and it seems to help sometimes, too. It might be worth trying. It is made for controlling urine spraying but the same directions seem to help with introducing new cats to the household and in decreasing aggression some.

I wish I could help more.

Mike Richards, DVM 9/13/2000

Getting cats to get along

Question: Dr Richards, Thank you very much for all of the valuable information that you have provided. Fortunately, everything checked out ok. We did not run blood work to check for hyperthyroidism, as Natasha was not eating any more than usual or losing any weight. There was no glucose/sugar in the urine, no crystals, and the concentration was perfect. I think it must just be the food, as the other cat also drinks alot of water. The new cat (Sugar) probably drinks less water than Natasha, because she eats less food. Anyway, I would like the 2 cats to be friends. I would like Natasha to use the litter box again on her own. What is the best way to socialize them? Your ideas and input on this subject would be very much appreciated. Thanks. Shari

Answer: Shari-

I can't offer a lot of hope for your situation. Cats that do not get along after three or four weeks together often will not ever get along. I have several clients who are doing exactly what you do in order to make the situation livable -- they make sure that the cat who is most bothered by the presence of the other cat has some private time with the litterpan and an hour or so a day alone in a protected spot, at least.

We have had some luck, recently, using Feliway (tm) spray to try to keep cats calm around each other. It has worked in a few situations that were are chronic as yours. The spray is actually made to stop urine spraying in the house but it seems to help in some cases of aggression between cats and since it isn't applied to the cats it should have no harmful effects.

Alternatively, buspirone (Buspar Rx) sometimes helps to limit aggression between cats, too. It has to be used very carefully, though, since it sometimes actually results in more aggression due to decreasing inhibitions. So a really mean cat may just get meaner but a cat that is aggressive due to fear is likely to be less aggressive when given buspirone. It is sometimes recommended to give the buspirone to the cat that is being attacked, to decrease its reactions to the other cat, which sometimes decreases the other cat's desire or need to attack.

We have only partial success with these approaches but they may be worth a try.

Mike Richards, DVM 9/10/2000

Aggression between housemate cats

Question: Dear Dr Mike

Historically, all of out cats have gotten along well with each other. In the past week or so, our four year old, neutered cat, Mulder, has started terrorizing the three other cats in our home. He is being especially nasty to his litter mate, Scully. He starts by chasing her around the house, cornering her and chewing on anything he can grab - like her legs- or pouncing on her as she walks by. It is not just playing, he is persistently nasty.

We started off by separating them as soon as he starts he comes back for more once the dust has settled. We are now squirting him with a water bottle once we see him pick on her, followed by locking him in another room for an hour or so until all has calmed down. This usually happens in the evening and he is also less loving and less demanding for attention than he usually is.

The background to all of this is we moved to Seattle three months ago and installed an Invisible Fence system (six weeks ago) to keep the cats on the property. Mulder was the first to explore and 'master' the system. He is now first out and last in at night and loves being outdoors.

On several occasions, we have found a neighbors cat sitting in our yard, on the other side of the Invisible Fence, watching our cats watch him. Mulder has gone after him in a nose to nose stare down on a couple of occasions but now the intruder cat just stays on the other side of the force field and glares at them. He did have two run ins with the other cat last week.

The only other visitor to the yard is a very dim squirrel that Mulder has befriended. Mulder sits about a foot away from the squirrel as it devours the bird food. Whenever I can I chase the squirrel off but the cat doesn't seem worried by its presence. There is construction going on in the lot behind ours but none of the cats seem worried by it.

As none of our attempts to stop this aggressive behavior have worked effectively, we are now at our wits end, do you think he is just spooked from the evil neighbor cat? How long do we give it before we look to drugs to alter his nasty disposition? Will giving him more (positive) attention change his behavior?

Many thanks - Elizabeth

Answer: Elizabeth- Well, you managed to list three of the most likely triggers for aggression between housemate cats all in one letter. That may make it hard to sort through the problem.

Moving seems to upset the balance between cats in a household fairly frequently. I am not sure why this is, but perhaps it is a need to establish new individual territories within the new home or maybe it is just insecurity and stress.

Cats who are indoor/outdoor cats have a stronger tendency to have territorial aggression than cats who stay indoors. I am not sure why this is, but it probably has to do with territorial pressures, such as urine marking, which they encounter outdoors. When cats who were previously indoor only are allowed to become indoor/outdoor cats there is sometimes a marked increase in territorial aggression.

When a cat feels challenged by an outsider, as is almost certainly happening between your Mulder and the outside cat he is having staring contests with, there is often an increase in aggression towards housemates.

Sometimes male cats just seem to grow into aggressive behavior. In dogs this seems to be an age related effect that has to do with social status but I don't think that really applies well to cats. Still, it seems like some male cats just get more and more territorial as they get older. So that may a contributing factor, too.

The dilemma you have is that Mulder likes to go in and out. This always makes it hard to decide how to deal with the aggression. One approach would be to keep him in and to keep the windows covered so that he doesn't feel threatened by the outside cat. However, this changes a lifestyle that he is fond of and it may not work now that the aggressive behavior has been triggered. An alternative treatment is to use an anti-anxiety medication, such as amitriptyline (Elavil Rx) or fluoxetine (Prozac Rx). Sometimes buspirone (Buspar Rx) can be helpful but it also sometimes increases aggressive behavior, so you have to be careful when using it. We have had some luck getting aggression to calm down some in multi-cat households by using Feliway (tm), which is a synthetic pheromone preparation. It is actually made to cut down on urine marking but it works by simulating a phermonally friendly environment, which does seem to help in some cats of inter-cat aggression.

Oddly, it sometimes helps a lot to medicate the cat that is getting attacked. In this case, buspirone does seem to be a good medication to start with. It relieves anxiety enough that the Scully might not induce attacks with fearful behaviors and if it does make her more aggressive towards him, that might resolve the problem, too.

Since you probably don't want to change Mulder's access to the yard at this time (just guessing) and since it is easier to use Feliway and less likely to cause any further problems, I think I'd recommend it as a first try, even though it may not work. If it doesn't, you will have to decide whether to try to limit Mulder's access to the outdoors and the threatening cat or to consider medications. That is going to be a harder choice.

I don't think that you can influence his behavior in this situation by increasing the attention he gets, but I could be wrong. There probably isn't any reason not to try this approach.

I wish I had a truly easy solution to offer.

Mike Richards, DVM 3/30/2000

Cats fighting after one visited Vet

Q: I am a subscriber to the newsletter and find the information helpful. I took Patches to the vet to have her teeth cleaned, since then her mother and sister have been spitting and fighting with her, about 8 days now. What causes this behavior and what can be done to change it? Also the vet has her on clindamycin twice a day until she finishes the bottle ~ 20 ml. Is this the usual dose and length of treatment?

Thank you. Linda

A: Linda-

I am not sure why cats that were living together peacefully find reasons to dislike each other after one of them leaves the house for treatment at the vet's but this is not an uncommon problem. Unfortunately, I don't have a lot of good advice about what to do when this happens. In most cases, the cats will eventually re-establish their normal relationship but in some cases they need help.

Sometimes just keeping the cats in separate rooms for a few days and switching them back and forth between rooms will allow them to get used to the idea that they have to live with each other again.

The product Feliway (TM), which is a synthetic phermone that is calming to cats can sometimes help cats make the transition back to normal relationships. Feliway isn't made to be sprayed on pets directly -- spraying it around the room at strategic spots like the corners of furniture helps to produce an environment that encourages calmness among the cats. Your veterinarian can get Feliway for you if you want to try it. This use is not what the label claim is for but there are some research projects that suggest it will help in this sort of situation.

The other alternative is to use an anti-anxiety medication and give it to one or more of the cats. If one cat is fearful it helps to medicate that cat as the the fearful behavior seems to incite things. If you can't identify which cat is the problem you might have to resort to medicating everybody. We have tried both approaches in our practice and have had more success when we could figure out which cats were anxious over the situation and treated them specifically than we have had when we have given up and treated everyone. One of the problem with this approach is that it is often necessary to give the medications for a month or more in order to keep the fights from re-occurring and then to taper the dosage off over a couple of weeks. Plus, it is best not to give medications if other approaches will work.

Clindamycin (Antirobe Rx) is usually used for at least 10 days when it is used for dental infections. For most cats, the entire bottle (20ml) is the right amount for 10 days dosing, as 1cc twice a day or 2cc once a day is the right dose for a 10 lb. cat -- or one that is within a couple of pounds of that weight in either direction. It can be repeated at intervals, if necessary, for chronic periodontal problems.

Mike Richards, DVM 5/5/99

Aggression between cats

Q: Dr. Mike, I just finished reading your information on Cat Attacks - ankle biting, etc. Your article indicated most cats chill after they get older, over 5 yrs. My problem is my cat seems to be becoming more aggressive with age. Our house had 3 cats. 2 male, 1 female. The 1 male/female were brother & sister. They always got along fine - after we had them for 1 yr - we adopted a kitten who was born from a stray street cat - the mother looked like a seal point siamese - but the kitten was black/white long hair - so we went from 2 to 3. Both existing cats had been neutered/spayed before "Spud"'s arrival. Spud got along well with the male but the female has never liked him - ever. Spud is now going to be 10 years old in October. The female just turned 11 in May and unfortunately, the peacemaker of the group had to be put down about 3 years ago - so now the house is 1 male and 1 female. The female still every single day, spits and hisses at Spud as if she hates him. We have all just accepted it.

Spud started "biting" us about 18 months ago. At first he just nipped the ankles now and then. You'd be petting him and he'd nip and run. The last 8 months he'd been really chomping down hard, drawing blood. The last attack was yesterday, I was lying in bed rubbing him, he was purring soundly, he moved to the pillow next to me to lay down - my son was next to him lying down also (son is 6 yrs old). My son was extremely still just laying there and Spud moved to him as if to rub his head on my son's forearm but instead he took a bite. A big bite, drew blood and then raced out of the room. He's bit my daughter while doing her homework, my mother while she was rubbing his back, etc. the list goes on. The bites don't seem to be provoked - they happen either during petting or after you stop. You can not tell when he's going to do it. The last time he bit someone before this last incident was 3 months ago - so it's not like it happens everyday. I'm getting concerned - my kids do not want anything to do with him and are getting more frightened of this fluffy adorable (for the most part) cat. Do you think he's acting out on his frustration of the female cat? Is the fact that he's 1/2 siamese have anything to do with it? He's on Science Diet Senior - goes to the vet every year and is proclaimed healthy - about 3-4 pounds over weight but healthy. He weighs about 14 pounds. Do you have any insight? Or could you recommend a behavioral specialist in my area - live in Anaheim Hills, CA. Thank you for your time.

A: M- I am not familiar enough with California to know how close you are to Davis, CA but there are good behaviorists there. For aggression it really does help a great deal to deal directly with a behaviorist if at all possible. This is not an easy thing to do in many areas of the country, unfortunately.

Cats and dogs do sometimes display "displaced aggression" - taking out their aggressive tendencies on something other than the inciting cause of them. Usually this happens right at the time of the aggressive frustration in dogs. A common example of this would be a dog that is inside a fence, barking at something outside the fence in an aggressive frenzy, then turning and biting a person or companion dog inside the fence with it. Cats may have a delayed response, possibly because they just stay aroused longer in aggressive situations. This may occur when the cat is prevented from carrying out an aggressive "attack" on another cat or is stimulated by territorial pressures that can't be relieved. That may apply in this situation since Spud doesn't like your female cat. If this is the case there is some chance that an anti-anxiety medication such as buspirone (Buspar Rx) may help -- but this medication will sometimes just lower the inhibitions against aggression and make it worse, too. I don't have any good suggestions other than that, though.

In an older cat exhibiting aggressive behavior that seems different from past behavior, it is best to rule out hyperthyroidism and to try to rule out other systemic illnesses as well. If specific testing for hyperthyroidism has not been done it may be worthwhile to do this even though your cat isn't exhibiting other signs of the problem.

If these attacks are truly happening for no reason it is going to be very hard to stop them.

If you are lucky enough to live near a behaviorist's practice it may be helpful to ask your vet to refer you for a consultation. Mike Richards, DVM

Cat aggression

Q: We had two cats, a male and a female. Two weeks ago, a stray female cat came to join the family. She was very friendly and happy to get along with everyone. Our other female, Tessa, obviously threatened by the new arrival, has made the most of every opportunity to attack the new cat. How should we best go about integrating these animals. We do keep them apart most of the time and only allow them to be together under supervision but this can't be a permanent option. Please could you give us some pointers as to what we need to do to make this a workable situation. Thank you for your time. Caroline

A: Caroline- It can be very hard to get cats to accept each other. In a situation in which the cats are outside cats or inside/outside cats it is especially difficult since it is harder to keep the cats separate for awhile while they get used to each other's smells and presence. In most cases these problems work out with time. I hope this is true for your cats. If not, I have very little practical advice other than that on the web site currently.

Mike Richards, DVM

Aggression between cats - medical therapy

Q: Dear Dr. Mike: I've read your postings on cat aggression and feel that you might be the one to help us with our problem. We have two 6 year-old, spayed females who were born in the house and have remained inside cats since birth. Tegan is a somewhat shy and rather gentle cat, normally very silent and non-vocal. Tootie is more outgoing, curious, and VERY vocal. The two have enjoyed friendly relations since birth. (Not much mutual grooming, but often they would sit side by side in the window watching birds, tails switching in unison, and would nap on the same bed.) Just recently, however, Tegan seems to have stopped recognizing Tootie and reacts to her as if she were a strange cat; e.g., hissing at her, running, hiding, and when cornered, attacking her. (No blood drawn so far, but I'm concerned about somebody losing an eye.) What is more astonishing, in this most silent of cats, she growls intensely, the growl rising to a scream as Tootie gets nearer. In six years I've never heard her do that. She also defecates and urinates during their fights. (Which they don't have unless she is cornered and can't evade Tootie, who just seems to want to find out what's wrong rather than actively go after her. Tootie will often adopt a submissive posture to try to get Tegan to lighten up. No dice.) On the advice of our vet we have resorted to keeping them separated, and have tried diazepam, (which seemed to stress them more) without success. We are at our wits end. Our vet says he's never seen anything like it as we can't account for the change by any sudden stressor or disruption of their routine and heretofore they have gotten along fine.

One thing I've noticed, Tegan seems to react strongly to Tootie's smell and my spouse has suggested a bath for each of them to see if that would help. I've also thought that boarding them out for a weekend, together (but in separate cages) might help. What do you think? We live in a small SW town and don't have access to an animal behavioralist. I'm sure our vet would be glad to try anything to help us solve this. Any ideas? We'd both appreciate it as this behavior is really disrupting our sleep. (Tootie bangs on our bedroom door and howls like a banshee when she wants in or out. Prior to this, they both had the run of the house.) Thanks for your site. It was comforting to read other postings from cat owners and realize we weren't alone in this. John-

A: Am sorry that I am so far behind in answering questions. If a physical exam reveals no sign of physical illness contributing to the behavioral problems it may be necessary to consider trying different medical therapies to see if one will work. Alternatives to diazepam include buspirone (Buspar Rx), amitriptyline (Elavil Rx) and fluoxetine (Prozac Rx). Buspirone is the medication I have seen recommended most often in these situations in the past. It has to be used cautiously until its action can be determined because it will occasionally cause an increase in aggressive behavior which is the opposite of what you are hoping for. Lately, it seems like Prozac is gaining favor among veterinarians due to its mechanism of action (sparing seritonin). This seems like a natural way to inhibit aggression since it seems to be tied to low seritonin levels. The major drawback is expense. Amitriptyline has a similar effect (it increases seritonin) but by a different action. It is a good choice if expense is important as it works well in some instances and is much less costly.

Medical therapy without identifying the underlying cause is not ideal but without the availability of a behaviorist it may be your only option. If medications work it is best to taper off the dosage and discontinue the medication, if possible, after a month or so of "normal" behavior.

Mike Richards, DVM

Severe Aggression Between Cats

Q: I would be most grateful for any information. OUR PROBLEM: Severe, injury causing aggession between two male cats. Both cats neutered, physiologically healthy. "Sebastion" is the aggressor - "Pippy" fights back when attacked but does not initiate attacks. This problem started about a year after Pippy joined the household. At first they played fine, then increasingly roughly, as time went on their rough play escalated into serious (injury causing) fighting. Sebastion was declawed as a kitten (before we owned him); he came to us as a one year old. Pippy was a stray - he was about 2 months old when we took him in, claws intact. Sebastion incurred so many injuries (and high vet bills) we finally resorted to declawing Pippy. He is much smaller (11 lbs. vs. 18 lbs.) but a "street mean" fighter. However, he never initiates attacks. Despite the fact that I keep them separated, Sebastion has developed a obsessive fixation with finding Pippy. Obsessively looking, sniffing, etc. - if he sees him through a screen or door, he will rip the screen apart with his teeth or try to destroy the door to get at him - quite psychotic behavior. When not obsessing about Pippy, he acts like his old normal, lovable self. Getting rid of one of them is not an available option.

Sebastion has been on on Buspar 15mg a day (5 mg t.i.d) which has helped only marginally. My Vet's other suggestion is Valium. I don't think a tranquilizer is the right approach or will help solve the problem. I have asked her about the effectiveness of psychotropic drugs like Prozac and Elavil but she is unfamiliar with using them. She is willing to work with me on this if I can find data about their use/safety/effectiveness on cats. Could you steer me to some credible sources of information on the use of pyschotropic drugs in cats. On-line info I could print up and take to her would be really helpful. My apologies for the long message and my deep gratitude for any assistance you can give us.

A: Aggression between cats is a difficult problem. In some cases it seems almost unresolvable. I have several clients who have finally just resorted to keeping their cats in separate parts of the house, all the time.

We have used medications for these problems and some of the time they either worked or the cats finally worked out their problems. It is always hard to tell which of those two possibilities really happened.

Amitriptylline is sometimes helpful when given to the aggressor cat. It is used by giving 5mg twice a day or 5 to 10mg once a day (the recommendation seems to vary and may be based entirely on the cat's response to medication).

Anti-anxiety medications can be helpful when given to the cat who is being attacked, IF the cat reacts with a great deal of nervousness or hair-raising and running away. That sort of behavior tends to egg on the aggressor cat. By using an anti-anxiety medication like diazepam (Valium Rx) or buspirone (Buspar Rx) in the "victim" cat to reduce these behaviors, the attacking cat may be less likely to be stimulated to attack.

I have not run across any information on using fluoxetine (Prozac Rx) in aggressive cats but that is being done in dogs, sometimes with apparent success, so it is possible it would work.

Good luck with this.

Mike Richards, DVM

Inter-cat aggression, new cat:

Q: Hi, We have three cats, two females 4 and 5 years old, and a male, 2 years old. All have been neutered and live pretty happily together. Recently we got custody of a fourth cat, a seven month old kitten. We tried to find a home for her while keeping her isolated in a bedroom. But no one seems to want her, so we decided to increase our little clan to four.The problem is that since we've begun letting the four spend controlled amounts of time together, trying to get them used to one another, there has been an incredible increase in aggressive behavior from the females. The kitten doesn't seem to understand what all the growling and hissing is about and tries to play with them, which just makes it worse. The male has adopted an "I don't care" attitude and stays out of it. It's only been a week since we started this. Do you have any suggestions that might make the transition easier, we don't want to have to put the kitten in the local shelter... Thanks!

A: Once you get more than two cats, the possibility of territorial aggression surfacing gets pretty high. By the time you have four or five cats, it is very high. It is hard to stop territorial aggression. Sometimes, it can help to separate the cats in different areas of the house for a few days. Switch the areas they are confined to so they get used to the other cat's smells, sounds, etc. Then reintroduce them. If that doesn't help, it sometimes works to use medications such as amitriptylline (Elavil Rx) in the aggressive cats. Some cats eventually work out the problem between themselves without intervention. The last resort short of giving up the kitten is just keeping them separate all the time. I have a several clients that do this in their multicat households. It isn't an ideal solution but it sometimes seems to be the only effective one. I hope your guys just adjust.

Mike Richards DVM

Inter-cat aggression:

Q: Dr. Mike, I have an interesting problem which I hope you have some advice for. We have two cats: Annie (6 yrs) and Dum-Dum (3 yrs). We had Annie for 3 months before we got Dum-Dum. Annie became the dominant cat. We moved in with another person with one cat. Annie remained the dominant cat while Dum-Dum and the other cat played all the time. This lasted one year and then we moved again and our household became a two cat household once again. But, Dum-Dum became the dominant cat. He became aggressive toward Annie and harasses her constantly. We thought this might be occurring because our apartment was rather small. We have moved into a much larger apartment and his behavior is still occurring. He chases her, bites her, and puts her in headlocks. Why did his behavior change and what can you do to correct it? We have tried spraying him with water and have verbally tried to correct his behavior. When Annie was dominant she was not this aggressive. Can you help?

A: In general, cats do not have the social structure that dogs do, so dominance behavior is less likely in them. Most cat disputes are territorial, predatory aggression that is redirected, or fear based. Sometimes play behavior in cats can look pretty rough, too. Many cats do not become territorial until they are 2 to 5 years of age, so it is likely that Dum-Dum is just developing normal territorial behaviors. Unfortunately, these behavioral patterns are a problem when cats must live together indoors.

It is pretty likely that the veterinary school at UCD has an animal behaviorist who can help you determine if territorial aggression is the problem and help in treating it. When possible, it helps a lot to consult with a good behaviorist.

In general, this is a difficult problem to deal with. If Annie is highly disturbed by the attacks and runs or hisses, she may be making the behavior worse in Dum-Dum, inadvertently. That would create a situation in which you might have to treat both cats -- Annie for the anxiety and nervousness that incites Dum-Dum to action and Dum-Dum for the aggressive territorial behaviors.

Medications can be useful in treating this situation. They do not always work, though. Sometimes people just resort to keeping the cats separate. If Annie isn't getting hurt (no bite wounds through the skin, abscesses, etc.) it may be OK just to live with the situation. If she is showing signs of stress from the attacks or is being injured, that isn't a viable solution.

Anti-anxiety medications like diazepam (Valium Rx) might help Annie cope. If she gets upset and runs or is easily induced to display defensive postures (tail up and fluffed out,etc.) it might actually decrease the incidence of the attacks to medicate her. If she is calmer, Dum-Dum won't feel the need to attack as often.

For aggressive cats, the anti-anxiety medications can work and medications that increase seritonin levels might help as well. Amitriptylline (Elavil Rx) has been used to treat the aggressor cat in situations like this with variable success. I am not sure if the newer medications like fluoxetine (Prozac Rx) are being used successfully or not. Dum-Dum might be more agreeable towards Annie if medications relieve some of his aggressive tendencies.

You can elect to separate them awhile and then try re-introducing them. Doing this by switching the parts of the house they occupy, trading their food bowls and litterpans, etc. can make give them a little time to get used to the idea of living together again. It can even help to allow them limited contact by putting Dum-Dum in a large dog crate and letting Annie have free roam of the house at the same time. Increasing the time of exposure to each other this way over a few days might give Dum-Dum the idea that he is invading her territory and make him a little less likely to be aggressive about "his" territory.

Good luck with this. Mike Richards, DVM

Aggression after spaying

Q: Dear Vet: I have male and female cats, two and one-half years old, who stay indoors and have been happily together since they were small kittens. He was neutered a long time ago. I just had her spayed six weeks ago. Three weeks ago she became very affectionate as if she were going into heat. That night they were looking at some raccoons out the window, and he must have startled her and she thought he was a raccoon in the house. She went after him and basically tried to kill him. They were streaking through the house, and I finally caught them and pulled her off of him and locked her up. Luckily, she didn't turn on me. She was howling like she was in heat. About 40 minutes later I let her out, and she did it again. By the time I got her this time, they both had drawn blood. I kept them separate for days, putting her in a cage in the same room as him part of the time. After four days, she seemed normal, and I let her out. They were so happy to be together, and were fine for almost three weeks. A few days ago, she was again acting agitated and very affectionate, and she went after him again with no provocation. They seemed to calm down pretty quickly, so the next day I let her out. They were fine for a few minutes, and then she did it again. She's staying agitated this time, still acting threatening towards him, and often howling like she was in heat. I'm really afraid that if I wasn't there, she would have gone on until one of them was dead. My male is twice her size, but he's scared to death. She's part Siamese, and has always been kind of a quirky little cat with some of that wild, warrior spirit, but never anything like this. She's a calico too, and I understand they can be kind of difficult. Everybody always said she was so nice for a calico. Have you ever heard of a reaction like this to being spayed? Can cats get hormone therapy like people can? If you have any insight or suggestions, lease let me know. We love them both very much, and this is heartbreaking. Thank you

A: There can be behavioral changes after anesthesia but they are reported to be short-term changes in most cases. I am not aware of an anesthetic agent used in cats which is associated with permanent behavioral change. As far as I know, these problems usually resolve within 2 to 3 weeks in almost all cases and sooner than that in most. I would not be willing to say that a permanent behavioral change could not occur, though. Another common problem is simply the separation of two cats who previously did well together, even for short periods of time. I have been answering question online now for five years and have been asked several times over the course of that time about sudden fierce territorial behavior in cats when one cat was ill, had surgery or was boarded separately from the other one for any reason. Several of the people who wrote saw this behavior after short durations of separation, even as short as an overnight stay. Many cats get more territorial at about 2 to 5 years of age and this may just be a manifestation of the need to re-establish a territory that gets way out of hand.

It can help to treat one or both cats with behavior modifying medications. If your male cat reacts to the attacks in a frightened manner, running away, hissing, spitting or lots of "hair raising" then it might help reduce the severity of the attacks to use an anti-anxiety medication like diazepam (Valium Rx) or buspirone (Buspar Rx) to reduce his reaction to her and less the number of attacks. It can also help to use medications like amitriptylline (Elavil Rx) or sometimes megestrol acetate (Ovaban Rx) in the aggressor cat. I'd be a little worried about using megetrol acetate in a female cat, though. Once in a while it seems to me that progesterone compounds make the female cats worse.

Sometimes, using medications for a brief period of time will help. It is also possible that pain relief medications like butorphenol (Torbutrol Rx) might help, just in case your female cat is feeling some pain she isn't expressing well post-surgery. You can also take the route of reintroducing the cats slowly to each other. Keep them separate for a week or two but change the rooms they are kept in so they smell each other's smells and hear each other. Then gradually reintroduce them, perhaps keeping the more aggressive cat in a crate for an extra day or so and letting her get used to seeing him and being near him before letting her out. This helps sometimes. Good luck with this. It is always a bummer to run into unexpected aggressive behavior when cats are separated, then reunited.

Mike Richards, DVM

Last edited 01/30/05


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...