Those who study which dogs bite most and why agree that firm breed-based statistics are tough to come by.
Whether such numbers are relevant is where they differ.
"Dog-bite statistics are not really statistics, and they do not give an accurate picture of dogs that bite," stated an article in the June 1, 2001, edition of the Journal of the American Veterinary Medical Association.
"Invariably, the numbers will show that dogs from popular large breeds are a problem. This should be expected because big dogs can physically do more damage if they do bite, and any popular breed has more individuals that can bite," said the article, which was a report of the association's canine aggression task force.
The Sept. 15, 2000, edition of that same journal featured a 20-year study of dog bite-related human fatalities, 1979-1998. During the final two-year period studied, "Rottweilers and 'pit bull'-type dogs accounted for 67 percent of human [dog bite-related fatalities] in the United States. … It is extremely unlikely that they accounted for anywhere near 60 percent of dogs in the United States during that same period and, thus, there appears to be a breed-specific problem with fatalities," the article said.
For the 20-year period, there were 238 dog-bite deaths for which a breed was known. The study lists 130, or 54.6 percent, as caused by Rottweilers, "pit bull'-types," or crossbreeds identified with those breed names.
The study adds caveats: Even if breed-specific bite rates could be calculated accurately, there still would be owners who wanted to bring out aggression in their dogs and were thereby drawn to certain breeds.
Fatal bites are rare and "should not be the primary factor driving public policy regarding dog bite prevention," the article said.
The article questioned breed-specific laws and noted that from 1975 to 2000, more than 30 breeds - including two dachshunds, a Yorkshire terrier, and a Labrador retriever - were responsible for fatal attacks on people.
"There is currently no accurate way to identify the number of dogs of a particular breed, and consequently no measure to determine which breeds are more likely to bite or kill," wrote Gail Hayes, a spokesman for the Centers for Disease Control and Prevention's Injury Center, in an e-mail to The Blade. The lead author was affiliated with the CDC when the study was published.
Then there was the article, "World's Meanest Dog: The English Cocker Spaniel?" posted in July on discovery.com, which cited a Spanish study that found a genetic factor for dominant-aggressive behavior in the breed.
Merritt Clifton, editor in chief of the publication, Animal People, said, "Aggression isn't really the most dangerous factor."
Since 1982, he has kept his own tally, "Dog attack deaths and maimings," by breed, which he collects from media reports and, secondarily, from humane society and animal-control reports in the United States and Canada. His log covers only attacks by pet dogs of a clearly identified breed type or ancestry as designated by animal control officers "or others with evident expertise."
His data, updated through Friday, show that "pit bulls," Rottweilers, Presa Canarios, and their mixes accounted for 79 percent of the 2,683 "attacks doing bodily harm" over that 27-year period, a category in his chart that includes all fatalities, maimings, and other injuries requiring extensive hospital treatment.
"Cockers act very macho," he said in a telephone interview. "But what's most dangerous with dogs is reactivity - when the dog reacts to something very quickly, decisively, immediately, and if what the dog does is bite, there can be a very severe consequence before the dog realizes itself what it's done is wrong."
Merely listing bite frequency by breed, even if possible to calculate, wouldn't do a lot of good, he said.
"The dog that bites once and disables someone is a much greater threat than the happy little dog that bites everyone and never hurts anyone," Mr. Clifton said.
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