Canine Aggression - Part 1
I want to start by saying, much of the information
I will
present, has come from Karen Overall DVM’s book, Clinical
Behavioral Medicine For Small Animals. Rather than trying to “reinvent
the wheel”, I used the wealth of information that was available
in her book. I have written articles on canine aggression, using
information from my own experiences plus what others had written.
Dr. Overall graduated from the University of Pennsylvania, School
of Veterinary Medicine in 1983, completed a residency in
Behavioral Medicine at Penn in 1989. She is a Diplomat of the
American College of Veterinary Behavior and is certified by the
American Behavioral Society as an Applied Animal Behaviorist. She
is currently on staff at the University of Pennsylvania, School of
Veterinary Medicine where she runs the Behavioral Clinic.
-Gary
Clemons DVM
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:
- Posture of the head, back and tail
- Position of the ears
- Activity of the tail
- Piloerection
- Eyes and mouth
- 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)
Hormones
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.
Author: Gary L. Clemons DVM
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