The hormone that could be making your dog aggressive discovered.

The hormone that could be making your dog aggressive discovered.Thousands of people are hospitalized every year for dog bites, and aggressive behavior is a major reason dogs end up in shelters. Biologists have studied the biology behind canine aggression, specifically the role of the hormones vasopressin and oxytocin. For some dog owners, a leisurely walk can turn stressful the moment their canine companion sees another pup walking by. Dogs with what is known as "leash aggression" may bark, growl or lunge at other dogs during walks, setting the scene for a tense and potentially dangerous interaction. So why do some dogs lash out on the leash while others don't? Hormones may be to partly to blame, according to new research led by the University of Arizona's Evan MacLean. Although a number of studies have looked at the role of testosterone and serotonin in aggression in dogs and other mammals, those hormones may be only part of the story, according to MacLean's findings, which are published in a special issue of the journal Frontiers in Psychology. MacLean and his collaborators looked specifically at oxytocin and vasopressin -- hormones that are also found in humans -- and found that they may play an important role in shaping dogs' social behavior.