When a dog has bitten someone, or come close to it, the word "bite" can mean very different things. A snap at the air and a bite that needs stitches are not the same problem, and they do not call for the same plan. That is why trainers, vets and behaviour professionals around the world use a shared tool called the Dunbar Bite Scale. It sorts bites into six levels based on what actually happened to the skin, not on how scary the moment felt.
Who created the scale
The scale was developed by Dr. Ian Dunbar, a veterinarian and animal behaviourist. He earned his veterinary degree at the Royal Veterinary College in London and a doctorate in animal behaviour from the University of California, Berkeley, where his research looked at social hierarchies and aggression in domestic dogs. He went on to design the first off-leash puppy socialization classes and founded the Association of Professional Dog Trainers.
He created the scale because a dog bite is a frightening, emotional event, and the way victims, owners and witnesses describe the same bite can vary enormously. One person's "attack" is another person's "nip". To take the guesswork out, the scale looks only at the physical evidence: whether the teeth touched skin, how many punctures there are, how deep they go and whether there is bruising or tearing.
That is the reason it caught on so widely. It gives vets, trainers, behaviour professionals, shelters, rescues and others one objective, damage based language for describing a bite. When everyone uses the same levels, it is easier to compare cases, share history between professionals and make sensible decisions about safety. The Association of Professional Dog Trainers still hosts an authorized version of the scale for its members and the public.
Here is how we understand each level, in plain language.
Level 1: No contact
The dog growls, lunges, snaps or air bites, but its teeth never touch skin. This is a warning. The dog is telling you it is uncomfortable, and it chose not to make contact.
Level 2: Teeth touch, no puncture
The teeth make contact with the skin but do not puncture it. There may be red marks, a light scrape or a small nick with a little bleeding from the teeth sliding across the skin, but no holes going straight in.
Level 3: Shallow punctures
A single bite leaves one to four punctures, none deeper than about half the length of the dog's canine teeth. There may be a tear in one direction, usually from the person pulling their hand away or the dog being pulled back.
Level 4: Deep punctures
A single bite leaves one to four punctures, with at least one deeper than half the length of the canine teeth. There may be deep bruising, which tells us the dog held on and bore down, or tearing in both directions, which tells us the dog held on and shook. This is a serious step up from Level 3.
Level 5: Multiple serious bites
The dog bites several times at Level 4 in one incident, or it has attacked more than once with at least one Level 4 bite each time.
Level 6: Fatal
The bite causes a death. Thankfully this is extremely rare.
Why we ask about bite history at intake
Every dog that comes to us for Behaviour Modification starts with a conversation about its history, and that includes any bites or near misses. We are not asking to judge you or your dog. We ask because the answer changes everything about how we work safely: who handles the dog, what safety gear we use, where sessions take place, and whether we need to bring in other professionals before we begin.
Please be honest with us, even if it feels uncomfortable. Owners often play down a bite out of love for their dog, or call a Level 3 a "nip". An accurate picture keeps your family, our team and your dog safe, and it helps us give you a realistic plan.
Lower levels usually respond well to work
A dog at Level 1 or Level 2 has shown a lot of control. It had the chance to do real damage and held back. In our experience, these dogs usually respond well to a structured plan, good management at home and an owner who follows through. That is not a promise, because every dog is different, but it is a hopeful place to start.
Level 3 cases can often be helped too, but they take more time, more commitment and more care around safety, and progress depends heavily on the owner sticking with the plan.
Higher levels need a careful team approach
Once a dog has bitten at Level 4 or above, the risk is real and the stakes are high. These cases need a full veterinary check first, because pain and medical issues can be behind sudden aggression. They also need a qualified behaviour professional and a careful safety plan before any training begins, which often includes muzzle training, strict management and clear limits on who interacts with the dog. Some of these cases are beyond what training alone can fix, and we will always be honest with you about that.
How we can help
We offer Behaviour Modification after a consultation, and every program is tailored to the dog and the family in front of us. There is no one size fits all plan, and we do not start until we understand your dog's history and what is driving the behaviour.
If your dog has bitten, or you are worried it might, do not wait for it to get worse. Getting a muzzle conditioned now is one simple step every owner can take. Our muzzle training article walks through it.
Keep reading
To learn more about how dogs show discomfort before they bite, read How Dogs Think, Learn and Communicate.