🐈 Cats
Why Is My Cat Doing That? Decoding Common Cat Behaviour
Litter box boycotts, 3am yowling, sudden biting, overgrooming: a lot of 'bad behaviour' in cats is actually an early medical sign in disguise. This guide shows you which quirks are harmless, which point to a health problem, and the one that's a true emergency.
The quirk-or-symptom problem
Cats hide illness better than almost any pet, and they express discomfort through behaviour rather than obvious signs. A cat in pain doesn't whimper; it stops jumping on the bed, or starts toileting outside the box, or grooms one spot raw. That's why so many "behaviour problems" turn out to be medical, and why guessing wrong wastes time an unwell cat may not have.
The sections below cover the behaviours owners ask about most, with the specific clues that separate a harmless habit from a health flag, and the handful of situations where you should get to a vet without delay.
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Litter box problems: rule out the bladder first
Toileting outside the box is the single most common feline complaint, and the first job is always to rule out a medical cause before treating it as behavioural. The urgent one is urinary blockage: a cat (especially a male) who strains, cries, visits the box over and over, and passes little or no urine can have a blocked urethra, which becomes life-threatening within a day. That is an emergency, not a training issue.
If there's no straining and your cat is otherwise well, the conversation shifts to the usual behavioural triggers: a dirty or covered box, too few boxes (the rule of thumb is one per cat plus one), a box next to the food or in a high-traffic spot, a sudden switch of litter, or stress from a new pet, person, or neighbourhood cat. A vet can help you decide whether a urine test comes first or whether you can start with box changes.
The cat that stops eating
Appetite loss matters more in cats than in most animals. A cat, particularly an overweight one, that eats nothing for more than 24–48 hours is at real risk of hepatic lipidosis (fatty liver disease), a serious and sometimes fatal condition that can start surprisingly fast. So "my cat is a bit off its food" is worth taking seriously rather than waiting a week to see.
Note what's changed: is it total refusal or just fussiness? Any vomiting, hiding, or weight loss? Did you change the food, or is there a new stressor? A vet can weigh your cat's body condition and the timeline and tell you whether this is a same-day concern or something to monitor with a specific plan.
Night-time yowling, especially in older cats
A senior cat that suddenly starts howling at night usually isn't being dramatic. In cats over about 10, loud night vocalisation is a recognised cluster that can point to an overactive thyroid (hyperthyroidism), high blood pressure, failing senses, or feline cognitive dysfunction (a dementia-like syndrome). Many of these are very treatable once identified.
Useful detail for a vet: your cat's age, whether weight has dropped despite a good appetite (a classic thyroid clue), whether they seem disoriented or stuck in corners, and whether the yowling comes with increased thirst. A quick blood pressure and thyroid check often settles it.
Overgrooming and bald patches
A cat that licks a strip of belly or inner-thigh fur bare is sending a message, but not always a psychological one. The identical pattern can come from fleas (even one bite in an allergic cat), a food or environmental allergy, mites, or ringworm, as well as from stress-driven overgrooming. The skin underneath is the clue: raw, scabby, or inflamed points more toward an allergy or parasite, while clean skin under missing fur leans more behavioural.
Rather than guessing, a vet will usually want to rule out the physical causes first (a flea treatment trial is often step one) before treating it as a stress behaviour. Mention any new flea exposure, diet change, or household upheaval.
Sudden aggression or hiding
When a friendly cat turns suddenly aggressive or starts hiding, pain is high on the list. Dental disease, arthritis (far more common in cats than owners realise), and injuries can all make a cat lash out when touched. There's also redirected aggression, where a cat worked up by something it can't reach (a cat outside the window) attacks whoever is nearest, and stays wound up for hours.
For a vet to help, note whether the aggression is triggered by touch (points to pain), by a specific sight or sound, or seems to come from nowhere, and whether anything physical has changed. The fix for a pain problem and the fix for a fear problem are completely different, so getting the cause right matters.
Reading feline pain: what to actually look for
Because cats mask pain, you learn to read the quiet signs: reduced grooming leading to a scruffy or matted coat, hesitating before jumping up or down, sitting hunched with feet tucked and eyes half-closed, a change in facial tension (vets use a validated Feline Grimace Scale), or simply withdrawing from the family. None of these are dramatic, which is exactly why they get missed.
If you're seeing a few of these together, it's worth a conversation. A vet can walk you through a structured at-home pain check and tell you whether it warrants an exam, rather than you waiting to see if it passes.
Key takeaways
- A male cat straining with little or no urine is a true emergency; go to a vet immediately.
- A cat not eating for 24–48 hours (especially if overweight) risks fatal fatty liver disease; don't wait it out.
- Always rule out a bladder/urinary cause before treating litter box issues as behavioural.
- Provide one litter box per cat, plus one spare, kept clean and away from food.
- Sudden night yowling in a senior cat often means thyroid, blood pressure, or cognitive change: all treatable.
- Cats hide pain; scruffy coat, reluctance to jump, and a hunched posture are quiet red flags.
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