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Canine Aggression Part 1

Definition of Aggression

Aggression is best defined within a given text as an appropriate or inappropriate threat or challenge that is ultimately resolved by combat or deference. (Overall, 1997)


It is important to realize that aggression can be an appropriate response in certain contexts. (Overall, 1997) An example is when a child is running through his own yard and a friend is chasing him. If the child is screaming, his own dog may feel he is being attacked by the other child and may go after the visiting child. In this context, the aggression may be appropriate. A dog barking at a stranger approaching his yard may be an appropriate response as well. Hopefully the dogs will be able to control their aggressive actions.


It is important to realize that dogs exhibiting inappropriate out-of-context aggression are not misbehaved or poorly behaved. They are clinically abnormal and must be regarded as such. (Overall, 1997)


For the dog’s behavior to improve, it is critical that the dog not be “provoked”. To do so, even unintentionally, only reinforces the inappropriate, undesirable, and perhaps dangerous behavior. (Overall, 1997)


Dominance aggression usually develops at social maturity, usually dogs 18-24 months of age. Signs of interaction can include standing very rigid, up on the toes, growling, hair up on the back, ears erect or slightly back, snarling, baring the teeth and wagging of the tail. If a dog is encountered showing any of these signs, it is also willing to interact in an aggressive manner if provoked. Simply staring at or reaching for these animals may be enough cause for the dog to attack.


Dr. Overall lists 6 factors to evaluate in canine communication that may forewarn you about an impending aggressive encounter:

  1. Posture of the head, back and tail

  2. Position of the ears

  3. Activity of the tail

  4. Piloerection

  5. Eyes and mouth

  6. Vocal: Barking-growling-snarling-lip lifting-snapping and biting


It is important to reemphasize that most aggressive dogs are clinically behaviorally abnormal and aggressive dogs should not be be described as vicious. Vicious is a term applied to humans which connotes an underlying emotional state that does not correlate well with canine behavior. “Dangerous” is a better description. (Overall, 1997)


In the United States more than 1 million people per year report dog bites and as many as 10 people die each year from these bites. Half of these bites leave scars and up to 30% result in time lost from work or school.


Most bites are inflicted by pet animals. In one study involving 3200 children 4 to 18 years of age, 45% reported having been bitten by a dog. (Jones & Beck, 1984) Because of children’s height, bites commonly occur in the upper extremities, shoulders, head, and neck regions. (Poderscek & Blackshaw, 1991)


Seventy-percent of dog bite related fatalities occur in children younger than age 10 and 10.2% occur in individuals older than 69 years of age. (Sacks et. al.,1989) Of 96 cases of dog bites reported in the Veterinary Record (1991), 85% occurred in the owner’s home, 62% represented adults bitten by their own animals, 75% of bites to children occurred when they visited neighbor or friends, 54% involved bites in which the victim was younger than 15 years of age and male dogs were responsible for most bites. Sustained attacks were more commonly reported for large-breed dogs such as German shepherds, Dobermans or Staffordshire bull terriers.


Most dog bites to children occur in the summer, most bites occur on weekends, and most often late afternoon or early evening. (Kizer, 1979) Most children and dogs are outdoors and active during these periods. (Clifford et. al., 1983)


When the human participants are children, they may be uncoordinated and appear unpredictable because of their sudden shifts in posture and vocal range when excited. Some behaviors and some intensities of behaviors in young children can frighten dogs and make them feel  threatened. Other behaviors like shrill squealing, could be misinterpreted by the dog as sounds and signals given by a prey item. Children can be unpredictable, dogs can be unpredictable, and the interaction can be toxic. (Overall, 1997)


Breeds that were overrepresented at the Behavioral Clinic at VHP, were Chows, Cocker spaniels, Dalmatians, and English Springer Spaniels. Borchelt (1983), found that purebred dogs were overrepresented when compared with mixed breeds only for one form of aggression: dominance aggression.


Physical factors that may affect the amount of damage caused by an aggressive dog include size (both mass and height), age (younger dogs rare more energetic and less constrained by physical disability), jaw structure and physique. Rottweilers and Doberman Pinschers, dogs with nasty reputations, are responsible for a small percentage of injuries requiring plastic surgery, whereas sustained attacks are most common in German shepherd, Doberman pinschers and Staffordshire bull terriers. (Vet Record, 1991)


Although male dogs are involved more often in aggression problems, neutering has little effect on this problem. Testosterone acts as a behavior modulator that makes dogs react more intensely. When an intact dog decides to react to something, he reacts more quickly, with greater intensity, and for a longer period of time. If the dog is reacting to a strange person or another dog, he will be quicker to bark, growl, or bite, and will continue for longer than a neutered male. (Overall, 1997) Castration decreases aggression in 62% of inter-dog aggression between male dogs. (Hopkins et. al., 1976)


A re-analysis of Borchelt’s (1983) data indicates the following.

·  Dominance aggression: Intact males represented more frequently than neutered males or females

·  Fear aggression: Intact females represented more frequently then intact males

·  Protective aggression: Neutered males represented more commonly than neutered females

·  Possessive aggression: Intact males represented more frequently than intact females and castrated males represented more frequently than intact females (Overall, 1997)


A very interesting observation was made by Dr. Overall in a preliminary study examining the effects of neutering on the behavior of dogs younger than 6 months of age and 12 months of age or older, one group stood out. Females younger than 6 months of age who were already showing signs of dominance aggression became more aggressive after ovariohysterectomy. This information, if reproduced by others, may be important as far as evaluating which animals are adoptable and which are not.


© Gary L. Clemons DVM

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