WHEN DOG OWNERS contact us for behavioral help, many people mention that their dog “nips” or that he’s “mouthy.” What does this mean? Is a nip different from a bite? What is the definition of a dog bite?

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There are several bite level scales that were created to define and communicate the differences between mouthing, nipping and an injurious bite. Understanding the difference is helpful in both preventing escalation of aggression and in eliminating it altogether. When we’re assessing what we can do to help an owner with a biting dog, we look at the circumstances in which the dog bit, as well as severity of the bite.

A few weeks ago, one of my staff at All Dogs Gym was greeting a new dog who was licking her face, when suddenly the dog put his mouth around her throat. Quick to react, the dog’s owner pulled him away. His action didn’t break the skin or injure her, so is this event worth noting? Looking at the most commonly used, six-level bite scale, it was. Here’s a description of bite levels:

The first level is considered “pre-bites.” Often it’s a nose bump or tag with the dog’s mouth either open or closed. Evaluating the dog’s other behaviors will help determine whether a nose bump is a Level 1 bite and should be considered an early warning sign. Level 1 bites are often remembered in retrospect after a more definable bite, or we’ll ask about it if there are other behaviors that might send up red flags.

Level 2 bites involve tooth contact with skin without breaking the skin. Owners often think of this contact as playful and commonly refer to it as mouthing or nipping. Again, it’s important to evaluate the dog’s other behaviors to determine whether this is a precursor to a more serious bite. In what’s called an inhibited bite, the dog doesn’t use force, so the teeth don’t break the skin.

Dogs are well able to control where their teeth go and the force they apply with them, so even though an inhibited bite doesn’t draw blood, it is still a bite and shouldn’t be ignored. Level 2 bites are often easily eliminated through positive-reinforcement training combined with behavioral and environmental management.

My staff member’s experience was a Level 2 bite. The dog put his mouth on her throat, but did not injure her. What was alarming was the location of the bite. A Level 2 bite to the hand or arm during play is not necessarily worrisome. On the other hand, a dog putting his mouth around someone’s throat was more than concerning, and we took this seriously.

Level 3 involves up to four bites that draw blood but are not deeper than half the length of the dog’s canine tooth. These bites might be either punctures or tears if the person pulls away, causing the tooth to lacerate the skin.

When a dog has inflicted a Level 3 bite, it’s important to work with an experienced professional trainer or behavior specialist to identify the triggers, desensitize the dog and provide guidance to protect both the dog and the people around him. It’s important to not use punishment or force. Using physical punishment to try to eliminate biting actually increases aggression.

Next are Level 4 bites, which are deeper than Level 3 and include bruising and lacerations from the dog shaking his head from side to side — called “prey shaking.” This bite level demonstrates that the dog lacks bite-inhibition and should be considered dangerous. Eliminating Level 4 aggression depends on many factors, not the least of which is strict owner compliance to behavioral, training, medical and management guidelines.

Levels 5 and 6 involve serious injury, mutilation and even death. Dogs that have inflicted this level of aggression are not safe to be around people — even their owners.

It is extremely rare for a dog’s first bite to be Level 3 or 4, yet it often takes an injurious bite before an owner will seek professional help. Virtually every biting dog that we have worked with provided many early warning signs, even starting lower on the bite level scale. Earlier behaviors were considered to be “playing” or accidental. Not so. It’s important for dog owners to seek advice and help before the biting escalates and someone is seriously injured.

Writing about a bite level scale is not intended to frighten anyone. Rather, my purpose is to explain that even an inhibited bite with no injury is still a bite. When in doubt, seek a consultation with a qualified professional trainer or behavioral specialist. Doing so may well save you and your dog from future tragedy.

Gail Fisher, author of “The Thinking Dog” and a dog behavior consultant, runs All Dogs Gym & Inn in Manchester. To suggest a topic for this column, which appears every other Sunday, email gail@alldogsgym.com or write c/o All Dogs Gym, 505 Sheffield Road, Manchester, NH 03103. Past columns are on her website.