Understanding Cat Behaviour: Early Signs of Illness and FIP

Cats have a reputation for being mysterious. Aloof. Unreadable. But spend enough time with a cat — really paying attention — and you realise they are communicating constantly. Every tail flick, every slow blink, every change in the pitch of a meow is information. The question is whether you know how to read it.

Understanding cat language matters for more than just bonding. It is how you notice, early, when something has changed. And in cats, behavioural change is often the first sign that something is physically wrong — long before more obvious symptoms appear.

How Cats Use Sound

Cats are remarkably vocal with humans — far more so than with other cats. Research from the Cornell Feline Health Center suggests that adult cats developed their meowing repertoire specifically to communicate with people, adapting their vocalisations over thousands of years of domestication. Here is what the main sounds mean:

Meowing. The most versatile sound in a cat’s vocabulary. A short, rising meow at the food bowl means something different from a long, drawn-out meow at 3am. Context is everything. Hunger meows tend to be insistent and repetitive. Greeting meows are brief and bright. A cat that meows more than usual — particularly if the sound is lower, more urgent, or accompanied by other changes — is worth paying attention to.

Purring. Most people associate purring with contentment, and often it is. But cats also purr when they are anxious, unwell, or in pain. Purring is a self-soothing mechanism — the vibration frequency (25–150 Hz) has been associated with bone density maintenance and tissue healing in research published in the Journal of the Acoustical Society of America. A cat that purrs while also hiding, refusing food, or running a fever is not purring from happiness.

Growling and hissing. These are unambiguous. Your cat feels threatened, cornered, or in pain. Do not force interaction. Give space. If growling or hissing appears suddenly in a cat that has never shown this behaviour before, it may indicate pain — particularly if the cat reacts when touched in a specific area.

Howling or yowling. A deep, prolonged, distressed sound. In older cats, this can indicate cognitive dysfunction or disorientation. In cats of any age, sudden yowling — especially at night — can signal significant pain or neurological disturbance. This is not a sound to dismiss. If your cat is yowling and you cannot identify an obvious cause, see a vet.

Chirping and chattering. The rapid, staccato sound cats make when watching birds through a window. Generally harmless and fascinating — thought to be a frustrated hunting response, or possibly a mimicry of prey sounds.

Reading Body Language

A cat’s body is a continuous broadcast. Once you know what to look for, you can read their emotional state at a glance.

The Tail

The tail is the most expressive part of a cat’s body and one of the easiest to read once you know the signals:

  • Tail held high, tip slightly curved: confident, friendly, happy to see you. This is a greeting.
  • Tail held high, quivering: intense excitement or affection — often seen when a cat greets someone they love.
  • Tail twitching at the tip: mild irritation or focused concentration. If you are stroking your cat and the tail starts twitching, stop — they are telling you they have had enough.
  • Tail lashing rapidly: agitation or anger. This is a warning before a swipe or bite.
  • Tail puffed up (piloerection): fear or extreme agitation. The cat is trying to appear larger.
  • Tail tucked low or between legs: submission, fear, or feeling unwell.
  • Tail sweeping slowly along the floor: frustration or predatory focus.

The Ears

  • Forward-facing, slightly outward: relaxed and interested.
  • Rotating independently: alert, tracking sounds in the environment.
  • Flattened sideways (“aeroplane ears”): anxious or overstimulated.
  • Pinned flat against the head: frightened or aggressive. Do not approach.

The Eyes

  • Slow blink: one of the most important signals in cat communication. A slow, deliberate blink directed at you is a cat’s way of saying they feel safe and trust you. You can return it. Research published in Scientific Reports (2020) confirmed that slow blinking by humans increases affiliative behaviour in cats.
  • Dilated pupils in normal light: excitement, fear, or pain. Context determines which.
  • Constricted pupils in low light: can indicate arousal or aggression.
  • Half-closed eyes: relaxed and comfortable.
  • Unblinking direct stare: a challenge or assertion of dominance. In an unfamiliar cat, avoid returning this stare directly.

The Body Posture

  • Loaf position (paws tucked under, eyes half-closed): relaxed and content.
  • Belly exposed: a sign of trust — but not necessarily an invitation to touch. Many cats will swipe if you reach for the belly.
  • Arched back, fur raised: fear or aggression.
  • Crouched low, head down: submission, fear, or feeling unwell.
  • Kneading: a comfort behaviour carried over from kittenhood. Usually a sign of contentment.

Why Constant Meowing Deserves Attention

A cat that suddenly starts meowing far more than usual — or whose meow changes in character, becoming lower, more urgent, or more distressed — is communicating something. Common causes include:

  • Hunger or thirst — check food and water first
  • Attention-seeking — particularly in cats that are bored or under-stimulated
  • Stress or anxiety — a new pet, a new home, a change in routine
  • Cognitive dysfunction — in older cats, disorientation can cause increased vocalisation, particularly at night
  • Pain or illness — this is the one that matters most. A cat in pain or feeling unwell will often vocalise more, particularly if the discomfort is persistent

If increased meowing is accompanied by any of the following — reduced appetite, lethargy, hiding, fever, or changes in litter tray habits — see a vet. Do not assume it is behavioural.

When Behaviour Change Is a Health Warning

Cats instinctively hide illness. It is a survival behaviour inherited from wild ancestors for whom showing weakness was dangerous. This means that by the time a cat’s behaviour changes noticeably, the underlying condition has often been developing for some time.

The behavioural changes most associated with serious illness include:

  • Withdrawal and hiding in unusual places
  • Reduced interaction with people or other pets
  • Decreased grooming — a dull, unkempt coat is often the first visible sign
  • Increased vocalisation, particularly at night
  • Reduced playfulness and activity
  • Changes in litter tray habits
  • Unusual aggression or irritability when touched

Any of these changes, sustained over more than 24–48 hours, warrants a veterinary assessment.

Behavioural Changes and FIP: What to Watch For

Feline Infectious Peritonitis (FIP) is caused by a mutation of the feline coronavirus. It is one of the conditions where behavioural change is often the earliest and most subtle warning sign — appearing days or weeks before more obvious physical symptoms.

A cat developing FIP typically becomes quieter. Less interested in play. Less likely to greet you at the door. They may eat less, groom less, and spend more time in one spot. These changes are easy to attribute to mood or age. They are not.

As FIP progresses, more specific signs appear depending on the form:

  • Wet FIP: visible abdominal swelling, laboured breathing
  • Dry FIP: persistent low-grade fever, gradual weight loss, increasing lethargy
  • Ocular FIP: eye cloudiness, colour changes, unequal pupils
  • Neurological FIP: wobbly gait, tremors, seizures, sudden behavioural changes including aggression or disorientation

Neurological FIP in particular can produce dramatic behavioural changes — a previously calm cat becoming aggressive, a confident cat becoming fearful, or a cat that suddenly seems confused about its surroundings. These are not personality changes. They are neurological symptoms.

For a complete breakdown of all 12 early warning signs of FIP, read our complete FIP symptoms guide. If your cat is showing any of these signs, read our step-by-step FIP action guide for exactly what to do next.

How to Communicate Better With Your Cat

Understanding your cat’s language is a two-way process. Here is how to communicate back in ways cats understand:

Use a soft, calm voice. Cats are sensitive to tone. High-pitched, excited voices can be overstimulating. Low, calm voices signal safety.

Slow blink back. When your cat slow-blinks at you, return it. Half-close your eyes, hold for a moment, then look away. This is one of the most effective ways to build trust with a cat.

Let them initiate contact. Extend a hand and let the cat come to you rather than reaching toward them. A cat that chooses to approach is a cat that feels safe.

Respect the tail twitch. When you are stroking your cat and the tail starts twitching, stop. This is not rejection — it is communication. Respecting it builds trust.

Pay attention to what changes. The most important communication skill is noticing when your cat’s behaviour shifts from their normal baseline. You know your cat. Trust what you observe.

Frequently Asked Questions

Why does my cat meow constantly?
Constant meowing can indicate hunger, attention-seeking, stress, or pain. If the meowing is new, more intense than usual, or accompanied by other changes like reduced appetite or lethargy, see a vet. Do not assume it is behavioural without ruling out a physical cause.

Does purring always mean my cat is happy?
No. Cats also purr when anxious, unwell, or in pain. Purring is a self-soothing mechanism. A cat that purrs while also hiding, refusing food, or running a fever is not purring from contentment — they are trying to comfort themselves.

What does it mean when my cat’s tail is twitching?
A twitching tail tip usually signals mild irritation or focused concentration. Rapid lashing indicates agitation or anger. If you are stroking your cat and the tail starts twitching, stop — they have had enough.

My cat has suddenly become more withdrawn and quiet. Should I be concerned?
Yes, if it persists beyond 24–48 hours. Withdrawal and reduced activity are classic signs that a cat is not feeling well. Combined with reduced appetite, hiding, or any fever, this warrants a vet visit. It could indicate many conditions — including FIP.

Can FIP cause behavioural changes in cats?
Yes. FIP — particularly neurological FIP — can cause significant behavioural changes including withdrawal, reduced interaction, sudden aggression, disorientation, and changes in vocalisation. These are neurological symptoms, not personality changes. Read our guide to neurological FIP and paralysis in cats for more detail.

How do I slow blink at my cat?
Make soft eye contact, then slowly close your eyes halfway, hold for a second or two, then look away gently. Repeat. This signals to your cat that you are relaxed and not a threat. Many cats will slow blink back.

Your cat is talking to you. Every tail position, every ear angle, every change in the pitch of a meow is information. The more fluent you become in reading these signals, the earlier you will notice when something shifts — and the faster you will be able to act.

If your cat’s behaviour has changed and you are concerned about FIP, read our complete FIP symptoms guide and contact a veterinarian familiar with modern FIP treatment today.

The FIP CURE Plus team is available in English and Arabic at info@fipcureplus.com.

View the FIP CURE Plus GS-441524 injectable range →

FIP CURE Plus — transparent, evidence-based GS-441524 treatment for cats across the Gulf.

Back to blog