Homing age influences the prevalence of aggressive and avoidance-related behaviour in adult dogs

•A questionnaire study on problem behavior in adult dogs in Finland was conducted.•Age of homing from domestic environments and problem behaviors were associated.•Dogs homed after 8 weeks had higher prevalence of aggressive and avoidance behavior.•Homing dogs raised in a domestic environment no later than at 8 weeks is indicated. Homing puppies before 8 weeks has been associated with lower instance of avoidance and types of aggression in adult dogs. The current study aimed to further assess the impact of homing age on these behaviours in adult dogs. Finnish dogs provide an interesting population for this further study, as based on the clinical experience of the co-authors, puppies in Finland are predominantly reared in domestic maternal environments before first homing, which was not the case in the countries where previous studies have been performed. Online questionnaire-based data on frequencies of problematic behaviours (n=3689) were analysed using Chi-Square, comparing adult dogs homed at 6–7 weeks (6–7), 8 weeks (8), 9–12 weeks (9–12) and 13–16 weeks (13–16). 31% were 6–7, 41% 8, 23% 9–12, 5% 13–16. If an overall association was observed, pairwise comparisons between homing age groups were conducted. All of the dogs included in the study came from domestic maternal environments, where the puppies were kept in the breeders' living quarters. Homing age was associated with avoiding, growling and snapping at unfamiliar people when away from the home environment (p=0.004, p=0.02 and p=0.008, respectively); avoiding, barking at, growling at and snapping at unfamiliar people visiting the home (p=0.02, p=0.02, p=0.04 and p=0.03, respectively) and barking at unfamiliar dogs when away from the home environment (p=0.001). With one exception, dogs homed later than 8 weeks, namely during weeks 9–12 and 13–16, had higher than expected prevalence of avoidance and aggressive behaviour than dogs homed at other ages. The exception being that for the measure, barking at unfamiliar dogs away from the home environment, there were higher than expected values in dogs homed at 8 and 13–16 weeks and lower in dogs homed at 6–7 and 9–12 weeks. This research supports the view that homing age is associated with instances of avoidance behaviour and some types of aggression in adult dogs.