Factors contributing to the likelihood of the development of dog aggression include:

  • Anxiety, fear or phobia
  • Lack of structure
  • Lack of proper exposure to other dogs during the critical socialization period
  • Early imprinting by an aggressive or nervous dam
  • A traumatic experience
  • Territorial behavior
  • Thyroid malfunction or other medical conditions
  • Abuse from owners
  • Medical or physical ailments
  • Breeding and genetic predisposition

Dog aggression manifests at the age of adolescence to social maturity (6 months to 4 years). Warning signs such as fear and/or nervousness around other dogs, displays of aggression only under certain circumstances (while on leash, in the presence of food, in the presence of the owner, etc.), or most commonly, over-the-top play behavior can be seen at any stage of the dog's development. Play behavior such as tackling, chasing, mouthing, nipping, pawing, and wrestling are all normal canine behaviors that serve the evolutionary function of preparing the young dog for later combat and hunting. Young dogs that engage in excessive amounts of these behaviors are much more likely to develop dog aggression as they age.

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a Feisty Fido???


Ian dunbar's bite scale

Level 1.

Obnoxious or aggressive 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 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 (little dog jumps, bites and drops to floor). 

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 N 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. 

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​Ian Dunbar Dog Star Daily 

1.  Identify the cause of the aggressive behavior

2.  Review medical records including blood work from your veterinarian.

3. Create a treatment plan to modify and/or eliminate the behavior

Aggression in dogs is defined by behaviorists as THE INTENT TO DO HARM.  

What do all the pictures on this page have in common?

All of these dogs have shown signs of Aggressive behavior at some point in their lives.  Some have bitten other dogs & people, others have simply shown displays of aggressive behavior including:

  • Barking
  • Growling
  • Air Snapping
  • Lunging
  • Muzzle Bumping
  • Biting 

2. Why Does aggression occur?

3. How can I help?

1. What is Aggression