Risk factors associated with stranger-directed aggression in domestic dogs

Abstract

Aggression in dogs is a safety concern both for humans and animals, and can lead to decreased animal welfare in affected dogs due to potential abuse, neglect, relinquishment or euthanasia. We examined risk factors associated with stranger-directed aggression in dogs using the previously validated, Canine Behavioural Assessment and Research Questionnaire (C-BARQ). Results are based on participant reports of dog behaviour. Data were analyzed using mixed logistic regression, with participant ID and country as random effects. Dogs (n=14,310) were more likely to demonstrate stranger-directed aggression if the participant rated them as mildly or severely fearful of strangers, or mildly, but not severely, fearful in non-social situations, when compared to dogs with no fear. There was an interaction between sex and neuter status, with neutered males being more likely to be aggressive than any other group. Furthermore, adult dogs were more likely to be aggressive compared to adolescents or seniors, and dogs were less likely to be aggressive if acquired as an adult when compared to being acquired as a puppy or adolescent. The random effects for country and participant were significant (p<0.001) with ICCs of 0.01 (CI: 0.00–0.08) and 0.40 (CI: 0.35–0.46), respectively, indicating that there was some correlation in behaviour among dogs within the same country and owned by the same person. The moderate effect of participant suggests that household effects need to be examined further. When looking only at dogs categorized as aggressive towards strangers (n=11,240), dogs were significantly more likely to be categorized as having severe aggression if they were male, and if the owner rated them as mildly or severely fearful of strangers, or mildly, but not severely, fearful in non-social situations, when compared to dogs with no fear. Breed group and where the dog was acquired also had an association with severe aggression. The random effects for country and participant were significant (p<0.001) with ICCs of 0.06 (CI: 0.02–0.15) and 0.34 (CI: 0.22–0.48), respectively, indicating once again that there was some correlation in behaviour among dogs within the same country and owned by the same person. These results suggest that variables related to the environment, owner experience and the dog’s level of fearfulness are associated with aggressive behaviour towards strangers in dogs. Therefore, it might be possible to identify dogs at risk of developing stranger-directed aggression and implement plans to prevent behavioural issues from developing.