World’s Meanest Dog: The English Cocker Spaniel?

A floppy-eared, innocent-looking breed may be one of the world’s most aggressive dogs, according to a new study that found English cocker spaniels tend to be more hostile than other breeds.

The discovery adds to the mounting evidence that aggressiveness is an inherited characteristic, suggesting that genes and breeding practices can both help determine how a dog will behave.

“In our country and according to our database, the English cocker spaniel is the breed that shows more aggression problems,” lead author Marta Amat told Discovery News.

Amat, a researcher in the School of Veterinary Medicine at the Autonomous University of Barcelona, and her colleagues analyzed 1,040 cases of canine aggression brought to a nearby veterinary teaching hospital from 1998 to 2006. Of those cases, the majority of cases were attributed to English cocker spaniels, Rottweilers, Boxers, Yorkshire terriers and German shepherds.

Probing the data further, Amat and her team discovered that English cocker spaniels were more likely than other dogs to act aggressively toward their owners as well as unfamiliar people. In contrast, dogs with reported behavior problems from other breeds tended to act aggressively toward other dogs. Among the English cocker spaniels, golden varieties and males were found to be the most hostile.

The findings, published in the latest Journal of Veterinary Behavior, confirm an earlier study conducted by a separate Spanish team from the University of Cordoba, which also found males and golden English cocker spaniels were more aggressive than females or those with black and mixed-color coats.

In terms of coat color, Amat explained that the coat pigment melanin shares a common biochemical pathway with dopamine and other brain chemicals involved in the control of aggressive behavior.