The Bite Scale

An Objective Assessment of the Severity of Dog Bites Based on Evaluation of Wound Pathology

Ian Dunbar PhD, BVetMed, MRCVS

Level 1. Fearful, aggressive, or obnoxious behavior but no skin-contact by teeth.

Level 2. Skin-contact by teeth but no skin-puncture. However, may be skin nicks (less than one tenth of an inch deep) and slight bleeding caused by forward, backward or lateral movement of teeth against skin, but no vertical punctures.

Level 3. One to four punctures from a single bite with no puncture deeper than half the length of the dog’s canine teeth. Maybe lacerations in a single direction, caused by victim pulling hand away, owner pulling dog away, or gravity (dog jumps, bites and drops to floor).

Level 3b. Multiple Level 3a. bites.

Level 4. One to four punctures from a single bite with at least one puncture deeper than half the length of the dog’s canine teeth. May also have deep bruising around the wound (dog held on for a number of seconds and bore down), or lacerations in both directions (dog held on and shook its head from side to side). 

Level 5. Multiple-bite incident with at least two Level 4 bites, or multiple-attack incident with at least one Level 4 bite in each. 

Level 6. Victim dead. 

For better communication between dog professionals, the scale may be refined with a decimal point. For examples, in a Level 2.8 “bite”, even though there were no skin punctures, the dog’s teeth left a mark and the “bite” hurt, or in a Level 3.2, yes the skin was broken but the “punctures” were little more than scratches.

The above list concerns unpleasant behavior and so, to add perspective: 

Levels 1 and 2 comprise over 95% of all dog “bites” and well over 80% of reported bites (tallied by the CDC). The dog is certainly not dangerous but much more likely to be fearful, or rambunctious and out of control. Wonderful prognosis. Quickly resolve the problem.

Level 3: The dog is not overly dangerous but much more likely to be fearful, or rambunctious and out of control. Without treatment, other Level 3 bites may follow with a slow, albeit predictable, increase in severity, especially if the dog is stressed (frightened, cornered, manhandled, etc.) Prognosis is fair to good with owner compliance. Quickly resolve the problem.

Levels 4: The dog has insufficient bite inhibition and is dangerous. Prognosis for resolution is very poor because of the difficulty and danger of trying to teach bite inhibition to an adult hard-biting dog and because absolute owner-compliance is rare. The dog is a Level 4 biter and is likely to inflict an equivalent amount of damage WHEN it bites again. I recommend that the dog is confined indoors and never taken onto public property. The dog is extremely reactive and stressed around (some) people and so walks would probably not be much fun for the dog anyway. Confining the dog to a fenced yard is not safe; the dog may not be able to get out but people (children) may be able to get in. 

Level 5 & 6: The dog is extremely dangerous and mutilates. The prognosis is dire. The dog is simply not safe around people. I recommend euthanasia because the quality of life is so poor for dogs that have to live out their lives in solitary confinement without physical affection from people. 

To add further perspective: Each year in the US, dogs kill approximately 20 people — half of them children. However, most years in the US, approximately 2000 children are killed, not by dogs though, by their parents.


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