Celia Haddon - Cat Expert

Understanding animals through their behaviour


Cats maintain social harmony by maintaining distance. Avoidance not conflict is their preferred strategy and we should aim to help our cats avoid each other, not try to force them to be friendly.

Aggressive behaviour includes staring, hissing, growling, chasing, biting, scratching, batting (Crowell-Davis et al., 1997). Most cats will spread themselves round an area with careful distances between each other. In a large cat colony there are often smaller family groups so a colony (or household) of 10 cats may have, for instance, two groups of three and one of four (Heath 2009).

We keep cats in an unnatural way. Individual cats vary in their tolerance for other cats. Cats eat and defecate alone: we make them share food bowls and litter trays and often expect them to eat and defecate in the same room (Heidenberg 1997). Domestic cat groups are dysfunctional because the cats are usually not related, ie not a family group. The actual territory is imposed upon them, rather than chosen by them – ie an indoor group may not have enough safe distance or the territory may be unclear because a cat flap lets in intruding strange cats. There may be too many cats in one house – more than five makes conflict much more likely.

If you observe carefully you will see which of your cats like each other and which don’t. Rubbing against each other, twining tails, or greeting each other with the tail up are a sign of friendship. Grooming each other is a sign of liking too. Sleeping together close enough to touch and facing each other shows friendship. Just sharing the sofa or lying back to back without touching is not a sign of friendship.

Chasing, hissing, ambushing and body blocking access (to food, owner, litter tray etc) are all signs of aggression. One cat may swipe at the other, if it gets too close – in doorways, near the cat flap, on the stairs, or on the sofa. Fearful cats will move away if the bullying cat seems to want its space. The bullying cat may spend time intimidating the victim by staring. The victim hides a lot, only eats or uses the litter tray when the other is not present. Bullying and intimidation may occur without actual fighting. What seems like “play fighting” may be a sign of aggression, if there is hissing, growling or mewing.  Most owners are slow to see these signs of dislike (Levine 2008).

Because cats are not very social animals, they do not have the appeasement signals used by dogs (Lindell 1997). Therefore aggression can become serious very rapidly. There are no signals to stop aggression (Heath 2009). There is no way to turn aggression off. Once a fight has taken place, then both cats are more likely to fight a second time. So it is vital to act as soon as possible to help the cats live in harmony. Do not let bad feeling develop. Sometimes the victim cat ends up terrified, and permanently unhappy.

Cats that have lived together happily, can sometimes have a breakdown in their relationship. Sometimes an outside intruder (another cat, a dog, or a fox) frightens the cats so much they they turn their anger on each other. If the cats are indoor cats, they may see the intruder through the window and then attack each other.

Group dynamics can also change when a new cat joins the household (Heath 2009). Or when a cat that has been a sort of mediator, spreading scent from one cat to another, dies (Bower 2012). Or when a mother cat starts chasing away a grown-up kitten or visa versa. Or when a cat is pregnant or nursing kittens. Sometimes time (ie pregnancy is over etc) will put this right. Or even when two cats are housed separately in a cattery and then brought back together again.

Sometimes the cause is smell. Cats identify friend and foe by smell rather than by sight – this makes sense to a twilight hunter. Friends smell of each other and of the home territory.This is produced by rubbing on each other or by grooming. Cats rub on humans to mix scents. A visit to the vet may mean one cat comes home smelling wrong. What could be worse than the enemy smell of the hated vet? The cat that comes home smelling of the vet, is therefore identified as a foe. Or one cat goes out and gets a different smell on it (ie like horse manure) and comes home smelling like an unfamiliar enemy.

The severity of the aggression must be judged by the unhappiness of the victim. It is not easy to “cure” long standing aggression between cats without separation within or without the home (Lindell 1997). Rehoming the victim will give it the chance of a peaceful and happy life. Forcing a cat to live in conditions of social stress is cruel and arguably against the Animal Welfare Act of 2006. If you love your cats, you won’t do this.


photo 1

Abcess from a bite

1. Does the victim need veterinary treatment?
2. Are there wounds — bitten ears, broken skin, blood etc? Abcesses.
3. Is one cat spending less time in the house because it is afraid to enter? It starts living in the garden no matter how cold the weather.
4. Is the victim spending its time hiding somewhere like under the bed?
5. Is the victim no longer grooming itself?
6. Is the victim too frightened to eat when the other cat is in the same area?
7. Is the victim too fearful to use the litter tray?
8. Is the victim no longer willing to approach you, because of fear of being attacked by the other.
9. Do you come back into the house to see signs of conflict – fur on the carpet or even blood?
10. Is the aggressor patrolling an area of the house so that the victim only has a small area of living space?
11. Does the victim lose control of its bowels or bladder – a sign of real terror?
If you answer yes to any of these questions, this is serious aggression. If the cat it has access to out doors the victim may soon leave home. My own feeling is that if you answer yes to more than three questions, you must rehome one of the cats. The victim is leading a life of almost constant fear. It is just not fair on the victim to expect it to live in this way. It is cruel to insist on keeping a cat that lives in daily terror.



High place with only room for one cat

1. Do not punish them when fighting. If you do, they will associate the other cat with the fear and pain of punishment. Ignore minor scuffles, because otherwise they will stage fights to get your attention or wake you up in the morning! Never force them to be close. Stop trying to make them friends. Think about helping them avoid each other instead.

2. Reduce competition and help them stay distant. Make sure there are plenty of cat beds in safe locations away from being jumped on, lots of scratching posts, a litter tray for each cat and one extra in different locations, lots of feeding bowls in different locations and lots of water bowls in different locations (Rochlitz, 2009). If the cats live in separate territories within the house, make sure there are litter trays and feeding bowls in both areas. Cats should be able to toilet without having to get close to each other.

3. Feed at separate locations or in separate rooms. Keep them apart before feeding time (Ligout et al 2020).

4. Install more than one cat flap. Sometimes a  cat will ambush one of the resident cats by sitting in front of the cat flap, now allowing the cat to come back in or go out. The cat flaps must be far enough away so that the ambushing cat cannot patrol both.

5. Install a PetPorte, www.PetPorte.com, or a SureFlap, www.SureFlap.co.uk,  cat flap within the house so as to make sure the bullied cat always has a safe retreat. These cat flaps work off a microchip, so they will open for one cat but not the others. SureFlap now have a large one for Maine Coons and big cats.

6. If they are indoor cats, or both spend a lot of time in one room, install a Feliway Optimum diffuser which will make the general atmosphere more relaxing. Relaxed cats are less aggressive.  In cases of severe aggression Feliway won’t work.

6. Fit the bully with a quick-release collar and cat bell, so that his victim or victims have advance notice of him coming and can get out of his way (Rochlitz 2009).

7. Guard against intruders or frightening wildlife by blocking off the sight of these, closing the cat flap permanently, or installing a microchip cat flap  (www.SureFlap.co.uk and Staywell Petporte). This is important, because if the cats may be attacking each other because of intruders.


Shed with flap and pots. Copyright Vicki Hardy

8. Make sure there are plenty of hiding places, preferably high up. Each cat should have a secure base, in its core territory. Cardboard boxes with entrance holes and windows are cheap – where cats can retreat if ambushed. Covered beds are similar. Put in high shelves, wardrobes, kitchen units where cats retreat to and look down from. Exits and entry areas can be difficult as cats have to pass each other, so consider a second cat flap, a chair on the landing (for a cat to jump up on while the other passes), etc.  Make sure routes to food or litter trays have these retreat areas so that a cat isn’t ambushed on a piece of open ground. This can be done in the garden too.

9. Install a retreat area in the garden for a bullied cat with a shed, microchip cat flap to keep out others, and pots around the flap to allow the cat privacy when leaving the shed.

10. If a vet’s visit triggered the aggression, take both cats to the vet’s surgery (one just for a trip) and make sure vet smells are wiped over both. Explain this to your vet! I have come across one pair of cats, where this put back the old loving relationship! All future visits should have both cats brought in.

11. Respite. Give the victim some respite care with a friend or relative where they can be the only cat. If they seem much happier (and the aggressor may be happier too) leave them in the new home.  For milder aggression, separate the victims at night putting the aggressor into a spare room with litter tray food etc. That will give the victim a chance to spend time in the home without  being bullied.


Cats can sometimes work out a relationship which is remote but not abusive. They may live in different parts of the house, or in different rooms, with separate litter trays. If this is an acceptable relationship to them, and neither cat seems to be suffering, then it should be acceptable to you. Accept their decision.


Here are some ideas.
1. Put a cat flap in the garden shed, install bed etc. and make one of the cats an outdoor cat. If aggression has been caused by taking a stray into the house, this will be a possible solution. The stray is homed but out of doors. Forcing a pampered cat to live in the shed would be cruel, but it would not be cruel to let a stray (used to living rough) become a shed cat.

2. Use a microchip cat flap (www.SureFlap.co.uk and Staywell Petporte)  to let the victim have its own area of the house with its bedding and litter tray there. This cuts down the amount of territory available to either cat so it is not an ideal solution but it is better than frequent conflict. Keep cats in separate areas of the house with separate cat flaps (catladder.blogspot.com for ideas)  to the outside world. To be fair, you will have to divide your time between the two areas or work out timeshare access for both cats.

3. REHOMING This may cause you emotional pain but may be the only way to relieve the pain and suffering of the victim cat. Truly caring owners should be prepared to do this. In the UK Cats Protection are a good rescue shelter. Make a donation. Before handing over the cat to a local rescue make inquiries about their euthanasia policy. Find a friend who will take the cat on. Some cats truly blossom when they live alone.


Bower, C., (2012), ‘Feline Aggression,’ APBC 2nd Annual Feline Conference Proceedings, 5-6

Crowell-Davis, S. L., Barry, K. & Wolfe, R., (1997), ‘Social Behaviour and Aggressive Problems of Cats,’ Veterinary Clinics of North America, Small Animal Practice, 27, 549-568.

Heath, S., (2009), ‘Aggression in cat,’ in eds: Horwitz, D. F. & Mills, D. S.,  BSAVA Manual of Canine and Feline Behavioural Medicine, Second Edition, Quedgeley, UK, BSAVA, 223-235.

Heidenberg, E., (1997), ‘Housing conditions and behavioural problems of indoor cats as assessed by their owner,’ Applied Animal Behaviour Science, 52, 345-364

Levine, E. D., (2008), ‘Feline Fear and Anxiety,’ Veterinary Clinics of North America, Small Animal Practice, 38, 1065-1079

Ligout, S.,   Xuemei, S., Vlaeminck, H. & Lyn, S., (2020), ‘Cats reorganise their feeding behaviours when moving from adlbitum to restricted feeding, Journal of Feline Medicine and Surgery, doi.org/10.1177/1098612X19900387

Lindell,E. M., Erb, H. N. & Houpt, K. A. (1997), ‘Intercat aggression: a retrospective study examining types of aggression, sexes of fighting pairs, and effectiveness of treatment,’ Applied Animal Behaviour Science, 55, 153-162

Rochlitz, I., (2009), ‘Basic requirements for good behavioural health and welfare in cats,’ eds: Horwitz, D. F. & Mills, D. S.,  BSAVA Manual of Canine and Feline Behavioural Medicine, Second Edition, Quedgeley, UK, BSAVA, 35-48


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