Signs of an Aggressive Dog

By Lynn Roberts, DVM


Q: What are the most basic signs that tell me a dog may be aggressive?

A: A dog’s motivation to bite might vary from case to case.  In general, the three most common types of aggression people need to be aware of are fear aggression, territorial aggression and dominance aggression.  All three present themselves differently and induce a dog to bite in different situations.  Therefore I will go over all three types and give you behaviour to watch out for that may indicate that a pet in your care may bite you as a result of one of these forms of aggression.


1. Fear Aggression: – Fear aggressive dogs may bite if they encounter an unfamiliar person or a person who engages in behaviours that induce fear, such as abrupt approaches.  Fearful dogs engage in typical behaviours, such as lowered body posture and tail position, ears pointing backwards and commissures of the mouth pulled back (fearful grin).  Single bites or snaps followed by withdrawal and submissive behaviours are common with fear aggression.  A person should not hug, stare at, punish or make any overt action toward this type of dog.  Speak in a calm manner and let the dog come to you.  If the dog is not exhibiting the typical postures of fear, reward the dog with a treat.  This will help reduce his/her fear on subsequent visits.


2. Dominance Aggression: – This type of aggression occurs typically if the dog is challenged over a resource that it values enough to engage in a fight.  The motivation to show aggression can vary between individuals as well as from situation to situation.  Dominant aggressive dogs engage in typical behaviours such as staring, head up, tail up, stiff gait, growling and baring the teeth.  These dogs resent being reached out to, patted on the head, pushed off favoured sleeping sites and having their food approached.  With this type of aggression, the bites tend to be multiple and severe. I advise anyone presented with a dog with this type of aggression to be very, very careful.  Avoid standing over or staring at the dog, petting the dog for prolonged periods (especially on the head or back), verbal or physical reprimands, removing an item from the dog or being close to food or food-related toys.  If a dog is showing any of these signs of aggression upon your first interview, take this very seriously. Severe physical harm to you may not be worth this particular client and his/her pet.


3. Territorial Aggression: – Territorial aggression is fundamentally protective and may therefore be partly fear-based.  The fear response is triggered by the perceived threat to a highly valued resource-the dog’s “home turf”.  Territorial aggression usually occurs in a specific area that the dog guards.  That area may vary in location and size.  Some dogs react aggressively if a person approaches their crate or bed.  Others show aggression towards intruders in the house, the garden or the area that surrounds the owner’s home.  Typical body behaviours can be the same as fear aggression (i.e. lowered body/tail posture and ears laid back) or in some cases that of dominance aggression (i.e. staring, head/tail up, stiff gait).  If the dog is known to be territorial over his bed or crate, it is best as a person to avoid these areas.  A dog that is territorially aggressive towards intruders in the home may not be a pet that can be cared for by a pet sitter.  Bites are typically a single quick bite or snap and these dogs usually withdraw afterward.  Unfortunately, territorial aggression tends to worsen over time.