Aggressive cats?

Heythrop Resort
Image source: author

Just before COVID-19 took over our lives I attended the International Society of Feline Medicine UK Congress held in Oxfordshire for vets and veterinary nurses.  At the beautiful Heythrop Resort we spent two days enjoying sixteen lectures on a wide variety of feline topics.  There were four great behaviour lectures about aggressive behaviour, training your cat to use an inhaler and also first aid advice we as nurses can provide to clients.  

One lecture was entitled "I'm not bad, I just do bad things: reframing our thoughts on aggressive cats", given by Vicky Halls, and in this post I will outline some of the main points I took home from this lecture. 

Image source: author

The first major point we learned that I want to highlight is that if a cat displays "aggressive" behaviour, it is a normal response (for the cat) to an event, NOT a temperament trait.  These responses are a normal part of predation, play and social conflict and essential for survival.  

However, human-direct aggression can be dangerous if it results in infected bite wounds, it can make handling cats challenging and can cause fear and distress to the owner, causing the owner-cat relationship to break down.  Not to mention potential effects on the cat: rehoming, punishment, distress and poor welfare.  

These behavioural responses to events stem from the brain, when it opts for the most appropriate behaviour to try and improve the situation.  There are thought to be seven motivational-emotional systems in the brain, according to Jaak Panksepp (2010).  These systems are involved in the generation of responses to different events or stimuli, both positive and negative.  

Panksepp 2010. Pain is actually considered part of the fear system but is 
an important factor when considering feline behaviour
Image source: author

In Sarah Ellis' lecture on feline communication she also explained further why cats happen to have these motivational-emotional systems.  Cats do not have the same cognitive ability as humans to discuss their emotions, reflect on them, understand how they shape behaviour or how they relate to experiences in the past.  In cats, they exist in the ancestral part of the brain responsible for "instinctual emotional arousal" - causing those innate behaviours that makes a cat a cat.  

Vicky Halls advises a helpful way to categorise aggressive behaviour for veterinary nurses and I feel these four categories should hopefully make sense to owners too. 

Click to enlarge
Image source: author
Content source: Vicky Halls, ISFM UK Congress 2020

The defensive response is one veterinary staff can see in practice.  If the cat experiences an approaching threat that is inescapable but far away, the cat will usually hide or freeze, making itself appear smaller.  If the threat comes closer and seems avoidable the cat will attempt to run away.  Once the threat is unavoidable the cat may resort to the fight response.  

Cats will only use the fight response if they feel it is necessary as this risks sustaining injury, which is not wise when the cat is responsible for feeding and taking care of itself. They will often give signals before resorting to swiping / scratching / biting, through body language cues.  Most veterinary practices now take measures to combat stress in cats visiting for appointments and those staying in for treatment, in order to reduce their anxiety about approaching threats, namely the staff!

Dr Sarah Ellis discussing feline communication at the ISFM UK Congress
Source: author

This defensive response is FEAR-BASED and may be affected by the cat's previous experiences.  Was the cat poorly socialised as a kitten and so has fewer positive associations with people?  Do they remember negative handling experiences?  Are they a naturally anxious cat?  Does the location or situation cause added stress?  

Cats that appear offensive have learned from previous experiences that the defensive "fight" method is the only response that will cause the threat to go away and will learn to use this approach again must quicker in future.  

So considering all this, it is important to move away from using the term "aggressive" for the cat, but rather use it to describe the behaviour if needed. Another commonly used term is "inappropriate" behaviour, but this also is misleading as the behaviour is appropriate to the cat!  If we consider the circumstances of the behaviour and what led up to its occurrence we can often decipher the emotion the cat is feeling and what may have prompted them to respond in this way.  

Colwyn Cats Protection foster cat Sammy, coming out of his hide to enjoy a chin
and cheek rub, rolling and kneading his paws, Sammy was given time to
make the first move and the hide is always there to retreat to if needed
Image source: author

Below I'll run through the advice given by Vicky Halls on preventing the most common behavioural responses and hope the points above have put "aggressive" behaviour into perspective.  

If any of you are experiencing aggressive behaviour with your cats, I would advise, as with any change in behaviour, to seek veterinary advice to initially rule out any health conditions that may be contributing.  If your cat is fit and healthy then hopefully your vets and veterinary nurses can offer advice depending on your individual circumstances.  If their first aid advice doesn't help then they can guide you to an accredited feline behaviourist for specialist advice. 

Prevention of defensive behaviour 

• Behave respectfully when interacting with your cat - this video from Sarah Ellis at International Cat Care runs through some key things to avoid when handling and you can see other great videos on their YouTube channel

• Allow the cat to initiate contact - the cat being in control is important to reduce anxiety
• Keep physical contact low intensity and of short duration - this is giving gentle fuss that the cat enjoys for a short period of time before they become too aroused or fed up!



Image from Vicky Halls' lecture ISFM UK Congress 2020

• Breeders of kittens should actively ensure they are well bred from parents with good temperaments, well socialised, are fed well, are raised in a low stress environment and to avoid early weaning as this can increase the risk of aggressive behaviour (Ahola & Lohi, 2017). 

Prevention of aggressive behaviour due to play/predatory/attention-seeking response

• Avoid inappropriate play with kittens - no teasing with hands or feet, using toys only. If kittens attempt to go for hands and feet, do not reward or reinforce the behaviour, distract with toys to redirect them onto a suitable target

Prevention of frustration related aggression

• Meeting all your cat's environmental needs is so important to prevent frustration. The AAFP & ISFM Feline Environmental Needs Guidelines describe everything cats need in their environment, based around the five pillars of a healthy environment (link below).

AAFP & ISFM Environmental Needs Guidelines

• Ensure the cat has unrestricted access to all its resources:  food, water, toilet areas, scratching posts, sleeping areas etc. 
• Provide enrichment such as play time and feeding enrichment - see my previous post Feeding our cats: "think outside the bowl" for ideas!
• Avoid play that may cause frustration such as using laser pens - always end a short laser session by throwing a toy or treat so the cat can achieve a kill!
• Ideally allow the cat unrestricted access outdoors
• Provide three dimensions of activity with places to get up high

RESOURCES

Free Downloadable Guides - Vicky Halls website

AAFP & ISFM Feline Environmental Needs Guidelines - full information on your cat's environmental needs

Aggression to humans - International Cat Care - lots of FAQs answered on this page

Understanding your cat's behaviour - CP guidance  -  more information on the natural behaviour of cats and interacting with them

Jaak Panksepp, 2010. Affective neuroscience of the emotional BrainMind: evolutionary perspectives and implications for understanding depression.  

Ahola & Lohi, 2017. Early weaning increases aggression and stereotypic behaviour in cats.

A new addition

Source: author

Whether it is your first cat or your next of many, preparation is key to give your cat the best chance of settling in smoothly.  

PREPARATION
Starting your cat or kitten off in a single room will help them to adjust from the confines of their foster pen or room into having more space.  All your cat's resources should be placed in this room ready for their arrival to minimise disruption when they are settling in:

• Food area
• Water placed away from food
• Litter tray(s) placed away from food and water
• The general rule is one per cat plus one extra!
• Toys
• Scratching facilities
• Your kitten will require a larger post as an adult so be prepared to upgrade
• Resting places
• A piece of bedding from their foster home will provide a reassuring familiar scent
• Hiding places
• igloo beds or even a cardboard box with comfy bedding
• High areas to escape and hide

A pheromone spray or plugin used in this room could help your cat to feel more at ease, for example Feliway Classic or Zenifel. These products mimic the facial pheromone and aim to relieve stress and promote a safe happy environment. Don't forget, Feliway Friends can help to reduce conflict between cats living together, so once your new addition needs to meet any existing cats Feliway Friends would be a good idea!  

Taz with his Feliway plug in
Source: author

International Cat Care also have some very useful tips:

• Avoid a room with full-length curtains that might be very inviting for kittens to run up!
• Assess the room and remove any potential hazards such as fireplaces, poisonous plants/substances or small hidey areas where kittens may become stuck. 
• Remove all breakable objects and secure cupboard doors
• Ensure windows are securely fastened
• Ensure kittens are not left unattended with toys on lengths of string

TRAVELLING HOME
My previous blog post Top Tips For Taking Your Cat To The Vets mentions the ideal type of carrier that allows for easier loading of your cat and suitable access to the cat when needed at the vets.  Again a pheromone spray in the carrier and in the car can help to make the cat feel more at ease - always allow 15 minutes before the cat enters the area after spraying.  It is best to cover the cat carrier with a light towel or blanket to help the cat feel safe as they like small secure hiding places. 

STARTING OUT
It is advised to allow your new cat time to adjust to their new surroundings on their own for a short while before expecting confident interactions from them.  

When approaching the cat, they will feel less threatened if you lower yourself to their level.  International Cat Care have produced a great series of videos for cat owners on how best to interact with cats: 

If your cat is not ready to approach you, do not force an interaction but sit and talk to them gently - make yourself inviting and wait for them to come to you. Try not to put a time limit on this, having patience is so important to allow your cat to remain in control.  

If you find your cat is continually hiding, it is still best to just give them more time, as long as they are coming out to eat and toilet. Make sure their food source is placed close to their hiding spot so they feel secure.  Treats and toys may encourage them from their hiding place - play helps to relieve stress and can be the first step of the bonding process without the need for physical contact. 

Cats Protection advise that kittens may need more intervention when settling in than adult cats as they may feel unsettled on leaving their mother and siblings. Make sure their cosy secure bed is at ground level, a low-volume radio may help to keep them company and you may need to indicate the location of their resources. 

MEETING EVERYONE
Introducing family members one by one will help to not overwhelm the cat - it is understandable for children to be particularly excited but they do need to be kept calm.  It is important to show children the most appropriate way to stroke and interact so the cat is always in control - any cat may defend themselves if they feel threatened or pushed too far.  During the first 8 weeks of their life, if your kitten has not encountered children, people of different genders, wearing different clothing, with different tones of voice, they may well be initially wary of anyone different to who they are used to. 

Source: author

Most cats will not feel confident to be picked up in the early stages and may never enjoy it - make sure you handle your cat in a way it is comfortable with.  Being picked up takes away the cat's control over the situation, which can lead to stress, causing them to try to escape. 

GOING OUTSIDE

Before your cat explores the rest of the house, a top tip is to use a soft cloth to gently wipe your cat's cheeks to pick up their facial pheromones.  This cloth can then be rubbed on points in the house at cat height to make the house smell more familiar. 

Source: author

Allow your cat to come out of their room of their own accord and keep the door open so they can hurry back to their safe area should they feel the need. Make sure all external doors and windows are shut so they can’t escape outside just yet.

Don’t let your cat outside until they have fully adjusted to their new home and know where their food will be coming from – this usually takes between three and four weeks. If your cat has not been neutered, don’t let them out unsupervised until the operation has been carried out by your vet. Kittens should always be supervised when outdoors. When you start to let your cat out, do it when they’re hungry so that you can tempt them back inside with food, until they are used to coming back to the house freely.  If you can train them to recall before going outdoors, even better!

RESOURCES:

Welcome Home - Cats Protection guidance on introducing a new addition to an existing cat or dog

International Cat Care: helping your cat/kitten settle

International Cat Care YouTube channel  - playlists covering cat handling for owners and training cats to improve well-being

Keeping cats safe in the garden - article by Alex Taylor "The Cat Nurse" and her cat Monkey

Check out my other blog posts on "Living in harmony" and "Top tips for taking your cat to the vets"

Feeding our cats: "think outside the bowl"

The "Think Outside The Bowl" campaign has been thought up by The Friendly Pet Nurse.  Cats are naturally designed to search, hunt, capture and kill their food, including small mammals and birds.  Only about 1 in every 4 hunts results in a kill, meaning around 40 hunting trips a day are needing to obtain 10 prey items.  This is a lot of effort used to meet their nutritional needs!

Our pet cats being fed from a bowl twice a day are not fulfilling this innate need to hunt and this can often lead to frustration and behavioural issues.  According to The Friendly Pet Nurse, scientific evidence shows that puzzle feeders can reduce the signs of stress, decrease aggression towards humans and other cats, reduce fear and anxiety, assist with weight loss programmes and reduce unwanted behaviours like inappropriate toileting problems.

A solution to this problem is to provide our pet cats with more interesting ways to obtain their food, promoting mental and physical stimulation. 

DIY Feeding Toys

Egg boxes

Source: author

A cheap and simple tool, egg boxes are a good starting point for a cat who hasn't used feeding toys before.  The cat can either use their paw to scoop the biscuits out or use their tongue and teeth to pick up the biscuits from the base.  

Paper parcels
To make the egg box more challenging, parcels of biscuits can be made using scraps of paper and placed in the egg box cups, so the cat has to unwrap the biscuits before eating them.  
Paper can also be used if shredded: hiding biscuits under a pile of shredded paper in a cardboard box makes a great foraging exercise!




Toilet rolls
Cardboard toilet roll inners are ideal for cats to investigate with their paws.  Rolls can be stacked on each other to make a puzzle feeder: Find out how to make a toilet roll pyramid here.

Scatter feeding
If your cat eats dry food, scatter feeding is very easy:  simply scatter around for your cat to forage for.  This could be indoors, in one area, food hidden in different areas, or outside scattering in the garden to forage in the grass. 

Commercial Feeding Toys

Source: author

Feeding ball
The Slim Cat feeding ball has different sized holes, selected by twisting the outer part of the ball.  The cat can start with the larger holes, being able to obtain the biscuits more easily before then using the smaller holes.  

This ball does encourage the cat to move around whilst feeding whilst negotiating the ball with its paws and nose.  

Trixie Cat Activity Fun Board
This puzzle feeder provides 5 ways to feed biscuits in 1! From the plastic globes to the tunnel your cat will need to use its initiative to obtain their food. Here is CP adopted cat Taran using his like a professional!

Source: author

Trixie Turnaround

Source: author

The metal rod can hold up to three blue containers, which can have different caps depending on the difficulty required.  It is best to start out with one container without a cap, so the biscuits can be obtained easily whilst the cat is learning to use it and then up the difficulty as they become more confident.

Once your cat is able to tip the containers they will then need to negotiate the biscuits from between the base prongs with their paws and claws.  

Your cat may need some assistance in flipping the containers whilst learning, with some owner demonstration possibly required!  Here is CP adopted cat Pepper getting to grips with hers and below there's Gin at Bridgend Adoption Centre.

LickiMat
Lickimats are very useful if your cat is on a wet diet or just prefers wet food.  These small squares are also ideal to wedge Dreamies into.  These cats certainly seem to be enjoying theirs!

All these commercial options are available online and make great investments for your cat's enrichment for years to come!  Rotating a combination of different options will keep feeding time interesting and novel to your cat and provide them with both stimulation and satisfaction.

Vaccinating your cat

Keeping your cats safe from infectious disease is an important part of responsible cat ownership.  Many cats we take in for rehoming have not had their vaccinations kept up to date as their owners were unaware of the need for boosters.  This post will cover the main points about vaccinating, with sources of extra information listed at the end. 

Pepper is a herpesvirus carrier with a
persistent eye ulcer
Source: author

Why should we vaccinate cats?
The reason for vaccinating is due to the potentially fatal prognosis for any cats who suffer from these diseases. If not fatal, the viruses often have long term effects on the cat, who will be a lifelong "carrier" of the virus.  For example, herpesvirus can cause painful eye conditions including ulcers. 

What is a vaccine?
A vaccine is a liquid suspension containing part of a virus or bacteria which triggers an immune response when given to the cat. The micro-organism in the vaccine has been altered in such a way to stop it causing disease but allows the cat to develop immunity to the disease without suffering from it.



How do they work?
The initial vaccine is given as two doses under the skin.  When the immune system is exposed to the altered micro-organisms the immune system recognises them as foreign and makes antibodies against them.  White "memory" cells are also generated by the immune system, which will be able to quickly reproduce these antibodies in the future when it is exposed to the disease-causing forms of the viruses. Future vaccinations, known as boosters, will boost the memory of the immune system by reminding the white blood cells of the antibodies necessary to fight these diseases. 

What are the vaccinations for?
All our foster cats receive vaccinations against the main diseases "RCP" and also FeLV:

Image source: author

Other vaccinations are available for:
Chlamydophila felis - bacteria causing painful conjunctivitis with discharge and redness of the eyes, but it can also be a cause of cat flu.

Bordetella bronchiseptica - bacteria causing flu-like signs such as sneezing, runny nose and eyes, high temperature and a cough. It can cause pneumonia and sudden death in kittens. The same bacteria cause kennel cough in dogs. 

Rabies - a lethal virus which is not currently a problem in the UK but cats travelling abroad under the Pet Travel Scheme must have vaccinations against rabies.

What are the benefits of vaccination?

Vaccines help to:

• Reduce symptoms of diseases caused by viruses
• Reduce the level of calicivirus shed by a cat (to potentially infect other cats) for up to one year after vaccination 
• Prevent death from panleucopenia
• Prevent FeLV from remaining in the blood 

When should we vaccinate our cats?
The first vaccine is given at 8-9 weeks of age, with the second injection 3-4 weeks later.  Current vets advise cats should be revaccinated against all components one year after the first vaccination course and then every year for leukaemia, and every three years for rhinotracheitis, calicivirosis and panleucopenia. Below I will mention the independent guidelines on vaccination protocols. 

Purevax RCP FeLV used for Cats
Protection foster cats
Source: https://shop.agrihealth.ie/

What about risks and adverse reactions?
Some cats may experience a mild reaction following a vaccination: this is normal as it shows the cat is having an immune response. Signs may include:

• Lacking energy / lethargy
• Poor appetite
• Tenderness at the injection site for around 24-48 hours after vaccination 

Other side effects that can occur include a high temperature, vomiting and diarrhoea, lameness and flu-like signs but these side effects are more likely to occur if the cat has already picked up another infection at time of vaccination – the immune system is then under too much stress to cope with everything.  Occasionally, a lump may occur at the site of injection and in very rare cases, cancers may develop in the same spot. 

Vaccination failure is rare but may result from storage issues, incorrect administration, failure of the cat's immune system to effectively respond if already compromised, the virus taking hold before the vaccination is given, or subsequent infection occurring from a strain of microorganism that was not included in the vaccine.  Vaccination failures and severe reactions to vaccines are very rare and the benefits of vaccinating far outweigh the risks involved. 

The Veterinary Medicines Directorate (VMD) run a surveillance scheme where members of the public and veterinary surgeons in the UK can voluntarily report any suspected adverse reactions (SARs) to veterinary licensed drugs, including vaccines. 

Veterinary Medicines Directorate Suspected Adverse Reaction reporting website
www.vmd.defra.gov.uk/adversereactionreporting/

The number of SARs reported after vaccination are very low in comparison with the thousands of cats suffering from infectious disease.

For more information check out the links below or book an appointment with your veterinary surgeon.  

So what's the latest advice?*

The WSAVA Vaccination Guideline Group and the European Advisory Board on Cat Diseases (ABCD) are independent bodies that maintain up to date guidelines on vaccinations for cats. Both bodies advise we should:

• Aim to vaccinate more individual cats
• Aim to vaccinate each individual cat less often and only with antigens that are necessary for that individual cat

Not vaccinating enough leaves the animal at risk of developing an infection and lowers overall immunity levels in the population. Over-vaccinating results in costs for owners and increases the risk for adverse reactions. 

To help make a decision we can consider the individual situation of each cat by assessing:

• The risk of contracting infections - indoor or outdoor cat? Single cat or multicat household?  Some vaccinated cats in the household may shed a virus without showing symptoms.  Exposure to other cats at boarding catteries, shows or vet practices?
• The risk of a significant infection developing - this is higher in kittens younger than 4 months of age and also in senior cats. The general health of the cat may have an impact and whether there are other stressors present such as poor nutrition or a parasite burden. 
• The likely severity of the disease in question - considering the nature of the disease and age/health of the cat
• Potential for spread of the disease - is the cat in a multicat household, does the cat visit a boarding cattery or cat shows
• potential adverse effects following vaccine administration - mild disease, allergic reaction, vaccine-related lumps or cancers

Martha Cannon summarised the international recommendations from the WSAVA and the ABCD on vaccination in cats in her lecture at the ISFM Feline Symposium for Nurses in Birmingham April 2019.  They reiterate that panleukopenia, herpesvirus and calicivirus are core vaccines to be given to all cats, with leukaemia being a non-core vaccine advised for cats with access to outdoors and make recommendations depending on different risk levels. 

Always consult your veterinary surgeon to discuss concerns regarding vaccinations and to make a tailored plan for your cat dependent on their risk level. 

References:

European Medicines Agency: Purevax RCP FeLV

Cats Protection Veterinary Guide on Infectious Disease and Vaccination

International Cat Care:  Vaccinating your cat

*Final section added following the ISFM Feline Symposium for Nurses in April 2019, vaccination lecture given my Martha Cannon, which was then published in ISFM's Feline Focus April 2020.  

WSAVA Vaccination Guidelines 

Keeping cats safe on Bonfire Night

This post comes from pet containment company Protectapet as we have come what can be a stressful time of year for cat owners - firework season. 

In 2014 pet insurers Agria reported 22% more pets go missing on bonfire night than any other night of the year. While fireworks can be beautiful and spectacular, without understanding the context it is easy to understand why cats mistake the explosions for a cause of serious anxiety. Here are our top tips for keeping your cats safe and calm even through a perilous time of year:

• Train your cat to recall from an early age: rattling the food bowls, shaking a treat-tin or giving a high-pitched call can alert your cat to return to your house from several gardens away.

Source: author

• Create lots hidey-holes and beds in your house: cats with more choices about where they can go to feel safe will be less anxious.

• Research when professional organised bonfires are on: the weekend evenings surrounding bonfire night and Halloween can be cause for human celebration.

• Plug in a pheromone diffuser such as Feliway at least a month before the firework season begins

• Call your cat inside several hours before darkness on the nights you know fireworks will be discharged. If you have SurePetCare Connect, a selective cat flap that allows you to control your cats’ access to the outdoors, you can set a schedule for when he or she will be allowed back outdoors on your phone.

• If you have concerns about your cat going missing before you get chance to call them inside for the evening, ProtectaPet offer cat-proof fencing or garden canopies to keep your cat safe outdoors and you’ll know where to find them even if they are too scared to move. 

Fencing can fit to an existing garden boundary.  Source: Protectapet

"Catio" coming straight off the house.  

Cat run with installed boundary fence

Cat canopy fully enclosing the garden

Find out more about these options offered by Protectapet on their website and in the following video: 

Source: cats.org.uk

Most of these points are covered in Cats Protection's firework guidance.  

There are also methods of desensitisation, which can be started in the spring/summer months by using a CD of firework sounds at a very low level and slowly increasing the volume over following weeks depending on tolerance - calming supplement company Zylkene provide some guidance on this.  

Dogs Trust also provide fireworks samples to download to use for desensitisation: Sound therapy for pets

Living in Harmony

Source: Cats Protection stock image

According to the PDSA PAW Report 2018, 43% of cats (that's 4.8 million) live in multi-cat households, with an average of 2.59 cats per household.  The report states that "14% of these cats – around 1.6 million – live with another cat they don’t always get along with and 6% of cats live with more than one cat but some aren’t keen on each other". 

The stress of living in a multi-cat household can result in unwanted behaviours: 77% of owners state that their cat performs at least one behaviour they would like to change but 74% of owners believed their cats were not stressed.  It appears there could be a lack of understanding in cat owners of the link between stress in cats and the development of unwanted behaviours.  


The root of how cats interact comes from their history as solitary predators.  Descended from the African wildcat, our cats are designed to hunt, eat, drink and sleep alone.  In fact all cats except lions, who live in prides, live in this way.  As people are a social species they often wish to keep more than one cat.  

African wild cat (Source: http://www.krugerpark.co.za)

Some cats do get on well together forming social groups and this is displayed by grooming each other (allo-grooming), rubbing against each other (allo-rubbing), sleeping cuddled up together, spending time together and playing.  This video produced by Cats Protection outlines whether your cats may be friends or foe.  By looking at these signs it is possible to work out which cats are in the same social groups.  

HOW TO HELP

Source: PDSA Paw Report, 2018

The video mentions the need for each cat in the household to have its own resources, the minimum of which include a food source, water source, litter tray, scratching post and resting area.  

The PAW Report (2018) looked at resources provided by cat owners with 2 or more cats:

• 66% provide 1 or 0 litter trays
• 55% provide 1 or 0 water bowls
• 73% provide 2 or fewer cat beds
• 16% provide only 1 food bowl

Despite many cats having to share resources 95% 
of owners state that their cat is happy.


Top tips for managing resources:

1. Keep food and water sources away from the litter tray - would you want to use the toilet in your kitchen?
2. Position food and water sources separate from each other - cats perceive water next to food as contaminated.
3. Follow the general rule of one resource per cat plus one extra.
4. Ensure the resources are suitable for the individual cats; for example different scratching options were discussed in my last post and litter trays were discussed in this previous post.
5. Position the resources in suitable places for the cats, not for owner convenience.  Would the cats rather not have to interact to reach their resources?  Do they spend time on different floors of the house?  Cats should be able to reach resources independently of each other.
6. Do not position resources near to entry/exit points and not at bottle-neck areas where cats would need to come into close proximity to each other
7. Clean litter trays regularly - cats hate soiled latrines, particularly when they smell of another cat.
8. Try to make their environment predictable with as much routine as possible. Unpredictability has been found to result in toileting outside the litter tray and reluctance to eat. 
9. Offer outdoor access that is predictable, which can promote natural behaviours such as territory marking and hunting.

Source: author

Feliway Friends is a synthetic pheromone product designed to mimic the appeasing pheromone given off by a mother cat to her kittens, to enhance their bond and promote harmony.  This can help to reduce conflict between cats and prevent fighting, chasing, blocking and staring. Find out more in this video from the manufacturer and also from their website - More about Feliway Friends

Source: protectapet.com

The neighbourhood cat population density can be a stress factor for both outdoor and indoor cats as cats can be observed through windows and they may enter via cat flaps. Solutions could include using frosting on exposing doors and windows to provide privacy (Purlfrost is one example), installing a selective entry cat flap (pet doors by SureFlap), using safe deterrents in the garden or considering a secure garden to exclude other cats: ProtectaPet supply purpose built fencing and enclosures, which would provide your cat with a safe and predictable territory environment.

Source: cats.org.uk

There is a lot more information on multi-cat households on the International Cat Care website: Multi-cat households and how to survive them and also in the Cats Protection Cats Living Together document.