Intraspecific killing in dogs: predation behavior or aggression?: a study of aggressors, victims, possible causes and motivations

Abstract

In the Netherlands, dogs may be seized by the police when they have killed or seriously wounded another dog. Police reports on these incidents reveal that some dogs attack vigorously and fast, without warning. In the veterinary behavior clinic at Utrecht University, these types of attacks were earlier recognized in referred dogs, leading to a set of diagnostic criteria for ‘‘dog-killing aggression’’ to distinguish from ritualized intraspecific aggressive patterns. To understand these vigorous types of attacks better, details from police reports and behavior test results of a group of 128 seized dogs and data gathered during behavioral anamneses of 151 referred dogs in a clinical setting were systematically analyzed to identify (1) the type of aggressors, (2) the victims, and (3) the possible factors underlying this intraspecific killing, including motivations. With respect to the aggressors, the population of referred dogs included a broad range of breeds with no breed outstanding. In contrast, in the seized dog population, 56% of the dog-killing dogs were of the American Staffordshire/pit bull terrier type. This difference might reflect owner characteristics with one group being less intended to ask for help in case of problem behavior or it could suggest a genetic, predisposition to react with dog-killing aggression in contact with other dogs or there may be combination of elements. These data, however, are not a proof of a genetic predisposition. In the seized dog population, 83% of victims were small-sized dogs of different breed types. The analysis of the anamnesis of the referred dogs, and voluntary remarks by owners of the seized dogs, revealed that the most frequently mentioned event precipitating this form of vigorous fast attack without warning was having been attacked by a dog somewhat earlier in life (36/24% of these referred dogs). Other, less frequently mentioned precipitating factors were insufficient socialization to other types of dogs during the primary socialization period (21/14% of these referred dogs) or showing a general tendency to prey on other species (9/6% of these referred dogs). The data suggest that for a number of dogs, aggression, rather than predation, was the underlying motivation, but that certain characteristics of the attacks strongly resemble predatory behavior. For the large majority of seized dogs, no information was available on their life history, which limits conclusions regarding causal factors. Therefore, predation cannot be excluded for some dogs. Dog-killing dogs may limit themselves to attacking the type of dog they had unpleasant experiences with before (specialists), or they may generalize their aggressive behaviors to several types of prospective victims (generalists) as found in the data. The consequence of these findings is that getting prior information on the type of victims and the precise details of the attacks are of utmost importance for testing, diagnostics, and making risk assessments. We plead for preventing escalating dog-dog aggression by management and training intervention and not letting the dogs “sort out their conflicts by fighting” because having been attacked by another dog may be an initiating event in some dogs to develop dog-killing aggression.