Why do dogs and cats show aggressive behaviour?

Aggressive behaviour may be caused by physical discomfort, pain, fear, stress, or social interaction problems. Start with a veterinary health check and provide a behaviour history for assessment. Behaviour specialist support may be needed.

How can I safely record an aggression video for my vet?

Keep a safe distance and avoid intervening. Use a steady camera to record the situation before and after the episode, and note the time, people present, and any other animals so your vet can analyse possible triggers.

How long does behaviour modification usually take to work?

It depends on the cause and treatment plan. Short-term improvement may be seen within a few weeks, but complete behaviour modification and stabilisation often take several months, with regular follow-up and ongoing records.

When should I seek a behaviour specialist assessment?

If aggression is frequent, has caused injury, or has not improved with general advice, seek assessment from a behaviour specialist or a vet experienced in behavioural medicine as early as possible for a long-term plan.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Canine and Feline Aggression: Behaviour, Assessment & Care Guide [2025]

Aggression between cats may stem from social stress or environmental factors. Consult a veterinary behaviour specialist first for assessment, and arrange health checks if needed to rule out medical causes.

Take 1 minute to check the symptoms first

Last updated: 2026/01/05

Pethealthmap editorial team

Sources: AVSAB, ISFM, National Taiwan University Veterinary Hospital

When to See a Vet

Immediate veterinary care needed (emergency)

•Persistent severe aggression causing bleeding in people or animals
•Confusion or seizures occur during aggressive episodes
•Aggression occurs together with obvious difficulty breathing

Schedule a veterinary visit as soon as possible (within 24-72 hours)

•Aggression frequency has clearly increased without an obvious trigger
•Defensive or aggressive behavior occurs whenever people or other pets approach
•Appetite or activity level has clearly decreased for several days

01What signs suggest something is wrong?

Aggressive behaviour is often accompanied by emotional and physical changes. Watch for the following behavioural and body signs.

Sudden growling, baring teeth, or biting people or objects
Marked mood swings, irritability, or ongoing tension and restlessness
Reduced appetite or a clear drop in activity
Defensive, evasive, or immediate aggressive responses when approached
Seek assessment early if attacks become more frequent or more intense

Seek emergency care immediately if you notice the following symptoms:

⚠️ Bite wounds or obvious bleeding need immediate attention
⚠️ A sudden increase in attack frequency with clearly stronger aggression

02How can I assess the problem at home? Key observations and when to seek emergency care

Recording aggressive incidents at home, along with any physical or environmental changes at the same time, helps your vet identify possible triggers more quickly.

Record the time, frequency, and context of each episode, including who was present
Use your phone to record videos of the aggression and any warning signs
Track food intake, water intake, and body weight changes each day
Observe and note any toileting changes or signs that may suggest pain
Mark possible triggers: people, other animals, or environmental factors
Bring videos and notes to the specialist consultation for your vet to review

03How will the vet diagnose it? Common tests and assessments

At the clinic, your vet will first rule out underlying medical problems, then carry out behaviour assessment and review your records.

Complete physical examination

checks for pain or physical discomfort

Blood tests and biochemistry

help rule out metabolic or internal medical disease

Urinalysis

checks for infection, kidney function concerns, and related issues

Diagnostic imaging, such as X-rays and CT or MRI if needed, to rule out structural problems

Behaviour assessment and video analysis to identify triggers and context

Referral to a veterinary behaviour specialist or advanced assessment when needed

04How is it treated and managed after diagnosis? Medication, diet adjustments and care guidance

Treatment starts with identifying triggers, then combines behaviour modification with environmental management and regular follow-up to monitor progress.

If a medical cause is found, follow your vet's treatment plan and attend follow-up checks
Create an individual behaviour modification plan based mainly on positive reinforcement
Adjust the environment to reduce triggers and stressors
Keep routines and diet consistent to support emotional and behaviour management
Return for regular reviews as advised to assess improvement and adjust the plan
Keep videos and observation notes as long-term follow-up records

05What should I prepare before seeing the vet? Key details that help identify the cause quickly

Prepare detailed records of when signs began, how often they occur, and the situation around each episode

Record aggression videos and note what happened before and after, including possible triggers

List current medications, supplements, and any allergy history

Record recent trends in diet, toileting, and body weight

Book ahead and mention that behaviour assessment or further imaging may be needed

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.

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