Abstract
The function of jealous behaviour is to facilitate the maintenance of an important social relationship that is threatened by a third-party, a rival individual. Although jealous behaviour has an important function in gregarious species, it has been investigated almost exclusively in humans. Based on functional similarity between dog-owner and mother-infant attachments, we hypothesised that jealous behaviour can be evoked in dogs, similarly to children. In our study owners focused their attention solely on the test partner, while they ignored their dog. We deployed familiar and unfamiliar dogs as social test partners, and familiar and unfamiliar objects as non-social test partners; all subjects encountered all test partners. Dogs showed more jealous behaviour, i.e. owner-oriented behaviour and attempts to separate the owner and test partner in case of social compared to non-social test partners. Results suggest that jealous behaviour emerges in dogs, and it is functionally similar to that in children observed in similar situations. Alternative explanations like territoriality, dominance rank can be excluded.