Cat behaviour problems: aggression, peeing outside the litter tray and stress

“My cat has become aggressive.” “She’s started peeing on the sofa.” “He hides all day and doesn’t come to say hello any more.” These are three of the sentences we hear most often in feline consultations, and all three usually come with the same question: is it a behaviour problem, or is something wrong with him?

The honest answer is that it is almost always both at once. In cats, behaviour is the first symptom of almost everything: pain, a urinary infection, thyroid disease, an environment that doesn’t meet their needs, or conflict with another animal in the home. That’s why, before looking for a trainer, a pheromone diffuser or a video online, the first step is always a full veterinary examination.

In this article we explain the three most common behaviour problems we see in cats — aggression, elimination outside the litter tray and chronic stress — which medical causes need ruling out in each, which changes at home actually work, and how we approach these cases at our clinic in Gràcia, Barcelona.

Why a cat’s behaviour changes (and why it isn’t “personality”)

The domestic cat is still, in essence, a solitary, territorial hunter that is also prey for other animals. That double condition explains much of what it does: it needs to control its territory, have escape routes and high places, eat in peace and, above all, never show weakness. A cat in pain doesn’t complain: it hides, becomes irritable, or stops doing things it used to do.

What we call “behaviour problems” are, almost always, normal responses from a cat to an abnormal situation: pain, illness, fear, a change at home, or an environment that asks more of it than it can cope with. Seeing it this way changes the whole approach: it isn’t about correcting the cat, but about working out what it is trying to tell us.

Aggressive cat: what’s behind it

Aggression in cats is rarely “bad temper”. It usually has an identifiable trigger, and telling which type it is changes the treatment.

Pain-related aggression

The most overlooked cause and the first one we look for. A cat that bites when you stroke its back, no longer tolerates being picked up, or hisses when jumping off the sofa may have arthritis (very common and under-diagnosed in cats over 10), dental pain, an ear infection, cystitis or abdominal pain. A physical examination, and sometimes an X-ray or blood tests, resolve many of these “aggressions” that were never behavioural.

Fear-related aggression

The most common type in cats adopted as adults or poorly socialised as kittens. The cat doesn’t attack because it wants to, but because it feels cornered with no way out: ears back, dilated pupils, body flat to the floor. The more contact is forced, the worse it gets. Treatment means giving the cat control — hiding places, height, never forcing — and moving at its pace.

Redirected aggression

The cat sees an unfamiliar cat through the window, gets aroused and, unable to reach it, discharges on whatever is closest: you, or the other cat in the house. It is sudden, looks “unprovoked”, and can leave the relationship between two cats broken for weeks. Identifying the trigger (often a stray cat in the courtyard) is the key.

Play aggression

Common in young cats living alone that have learned to play with hands and feet. It isn’t an aggression problem but a lack of appropriate stimulation: more play sessions with a wand toy or moving toys, never with hands, and predictable routines.

Conflict between cats in the same home

Two cats that “suddenly” can’t stand each other have usually been living with silent tension for a while: one blocks the way to the litter tray, the other eats while keeping watch. Scarce or badly distributed resources (a single tray, a single bowl, a single high bed) are behind most chronic conflicts.

Cat peeing outside the litter tray: body first, tray second

It is the most frequent feline behaviour complaint, and the one that breaks the most cat–human relationships. One thing should be clear from the start: a cat does not pee outside the tray out of revenge or to “annoy” you. Either it has a physical problem, or the tray doesn’t work for it, or it is marking territory because of stress.

Medical causes that must always be ruled out

• Feline idiopathic cystitis (FIC): bladder inflammation closely linked to stress. The cat associates the pain with the tray and starts urinating on soft, cool surfaces (bed, bathtub, sofa). It is the number one cause in young and adult cats.
• Crystals, grit or urinary obstruction: especially in males. If your cat goes to the tray, strains and produces nothing, or only a few drops with blood, it is a same-day emergency: an obstruction can be fatal within 24–48 hours.
• Chronic kidney disease, diabetes or hyperthyroidism: make the cat drink and urinate far more; sometimes the tray simply can’t keep up, or the cat doesn’t get there in time. We cover it in our guide to chronic kidney disease in cats.
• Arthritis: an older cat with painful hips or knees may be unable to climb into a high-sided tray, or to crouch inside it.

All of this is assessed with an examination, urine and blood tests and, in many cases, a bladder ultrasound, done at the clinic and without sedation in most cats.

When the problem is the tray

If the tests are normal, it’s time to look at the tray through a cat’s eyes:

Urine spraying: a different thing

Spraying is urine sprayed on vertical surfaces (walls, doors, furniture), in small amounts, with the cat standing and tail raised. It isn’t a litter tray problem: it’s a sign of territorial stress. The usual triggers are stray cats seen through the window, a new animal or person in the home, building work, moving house or changes in routine. It is managed by reducing exposure to the trigger and, when necessary, with medication under veterinary supervision.

Chronic stress: the problem that doesn’t look like one

Many “healthy” cats live with a background level of stress that nobody identifies because it makes no noise. It shows up as hiding more than usual, licking bald patches on the belly or legs (over-grooming), eating without appetite or not eating, frequent vomiting, recurrent cystitis, or a cat that “has just never been affectionate”. Indoor cats, who depend 100 % on the environment we give them, are especially vulnerable — we explain it in our guide to indoor cats’ needs.

How we approach feline behaviour at Rovira

Our clinic specialises in feline medicine, and that shapes how we work these cases from the moment the cat comes through the door.

1. Detailed feline history. Before touching the cat we ask about the home: how many cats, how many trays and where, what it sees through the windows, what has changed at home in recent months, how and when the problem started. Very often the answer is already here.
2. Low-stress examination. A cat that arrives tense can’t be examined properly by force. We work in a quiet room, with no dogs, with time, letting the cat explore before we touch it. If you’re on your way, our guide to taking your cat to the vet without stress helps a lot.
3. Rule out pain and disease. Joint and abdominal palpation, oral check and, depending on the case, blood and urine tests, ultrasound or X-ray. Without this step there is no talking about “behaviour”.
4. Environment and handling plan. With the results in hand, we define concrete, realistic changes at home: number and type of trays, distribution of resources, managing windows, play routines, introductions between cats.
5. Referral when needed. If the case requires an in-depth behaviour modification programme or long-term medication, we refer to a veterinary behaviour specialist and follow the case with them. We know where our part ends and the specialist’s begins.

When to book an appointment

• Any sudden change in behaviour in an adult cat.
• A cat that pees outside the tray for the first time, even just once.
• A male cat that goes to the tray and can’t urinate: the same day, no waiting.
• Aggression that appears when you touch a specific area or pick the cat up.
• Bald patches from licking, habitual hiding, not eating or not grooming.
• Before introducing a second cat or moving house, if your cat is already sensitive to change: preventing is far easier than reversing.

If your cat has changed and you don’t know why, book an appointment at our English-speaking clinic in Gràcia. We start with what a cat can’t say in words: whether something hurts.