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What Makes an Aggressive Dog?

Study suggests it's not so much the breed as the gender, training, origin and owner's age

WebMD News from HealthDay

By Dennis Thompson

HealthDay Reporter

FRIDAY, Feb. 28, 2014 (HealthDay News) -- You see a Rottweiler standing next to a poodle and a Chihuahua. Which dog is most likely to bite you?

To answer that question, don't look at the dog, British researchers say. Instead, look at the owner standing beside it.

A dog's breed is only one of many factors that influence its capacity for aggression, according to a new study published recently in the journal Applied Animal Behaviour Science.

More telling clues to aggression might be the age of the owner, the training the dog has received, the place the dog was obtained and the gender of the dog, the researchers found.

In addition, dogs that are aggressive in one situation likely will not be aggressive in other situations. For example, a dog that might lash out on the street could be perfectly peaceful in its own back yard.

"Aggression is incredibly complex. It's going to be both situation-dependent and dependent on the history of both the people and the dog," said Stephen Zawistowski, science adviser to the American Society for the Prevention of Cruelty to Animals (ASPCA). "You can't just pick the breed of the dog and say somehow that will be predictive of whether the dog will be aggressive."

Zawistowski, who is also an adjunct professor of anthrozoology at Canisius College in Buffalo, N.Y., was not involved with the new study.

For the study, Rachel Casey, of the University of Bristol's School of Veterinary Sciences, and colleagues distributed about 15,000 questionnaires to dog owners regarding dog aggression toward people. About 4,000 were returned.

The researchers found that owners reported dog aggression toward unfamiliar people more often than aggression to family members.

Nearly 7 percent of owners said their dog barked, lunged, growled or actually bit unfamiliar people who came to their house. Meanwhile, 5 percent reported these aggressive behaviors when meeting people while out on walks. By comparison, only 3 percent of owners reported aggression toward family members.

The results showed that a majority of dogs were aggressive only in one of these three situations. A dog that would lunge at a strange person on the street was not likely to lunge when a strange person approached their house.

In breaking down factors associated with dog aggression, the researchers found much more than the dog's breed at work. For instance:

  • Dogs owned by people younger than 25 were nearly twice as likely to be aggressive than those owned by people older than 40.
  • Neutered male dogs were twice as likely to be aggressive as neutered female dogs. However, there was no significant difference in aggression risk between neutered and non-neutered males.
  • Dogs who attended puppy-training classes were about one and a half times less likely to be aggressive to strangers.
  • Dogs trained using punishment and negative reinforcement, however, were twice as likely to be aggressive to strangers and three times as likely to be aggressive to family members.
  • Dogs obtained from animal rescue and other sources were much more likely to be aggressive than those bought from a breeder.

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