Current Science, Sept 14, 2001

The fatal mauling of a San Francisco woman raises the question: Why do dogs turn deadly? One night last January, Diane Whipple, 33, was unlocking the door to her San Francisco apartment when two large, snarling dogs lunged down the hallway at her. Trailing after them was one of the dogs' owners, Marjorie Knoller, who lived in the apartment adjacent to Whipple's.

Neighbors heard Whipple screaming as one of the dogs, a 54-kilogram (120-pound) male Presa Canario mix named Bane, attacked her. The second dog, Hera, a slightly smaller female dog of the same mixed breed, joined in. When police arrived at the scene, they found shreds of clothing strewn along the hallway, bloody handprints on the walls, and Whipple lying on the blood-soaked floor. The sight was so horrific that rescue workers later needed trauma counseling.

Whipple, a lacrosse coach at St. Mary's College, was rushed to a nearby hospital, where she died from neck injuries sustained during the attack. As for the dogs, Bane was euthanized, and Hera was sent to an animal shelter. Euthanasia is the act of killing a person or an animal painlessly for reasons of mercy.

Bred to Be Bad

What makes dogs turn deadly? Experts in dog behavior say some breeds are more aggressive than others. Dogs were first domesticated, or tamed to live with humans, from wolves thousands of years ago. Since then, people have selectively bred, or mated, certain types of dogs to emphasize specific behavioral traits that are helpful to humans. Those traits include fighting, guarding, hauling, herding, and hunting.

Certain breeds of guard and fight dogs are involved most often in fatal attacks on humans. A recent study in the United States revealed that rottweilers (guard dogs) and pit bulls (fighters) were responsible for roughly 60 percent of the more than 300 fatal attacks that have occurred during the last 20 years.

Killer Instinct

Though rottweilers and pit bulls are involved in deadly attacks more often than other breeds, experts say it's impossible to tell a killer by breed alone. One of the best predictors of canine aggression is whether a dog has been neutered, or surgically stripped of its sex organs. Dogs that haven't been neutered experience hormonal surges that drive them to roam and fight. Hormones are chemical messengers that control body processes and behavior. Neither Bane nor Hera had been neutered.

Another factor that might have been involved in the Whipple attack was predatory aggression. Predators kill other animals for food or to defend their territory. Dogs have evolved from wild canines, and most wild canine predators kill in packs. Evidence from several hundred fatal dog attacks suggests that some domestic dogs will return to those savage instincts when they gather in a pack. "Frequently it's a small pack of two to five dogs that work as a group and down some prey--most often a child or small adult." Diane Whipple--who was just 1.6 meters (5 foot 3 inches) tall and weighed only 50 kilograms (110 pounds)--was bitten in the leg and dragged to the floor by one dog as the other dog attacked her throat.