Dogs' endocrine and behavioural responses at reunion are affected by how the human initiates contact.

For dogs, humans are likely to be the most important feature in their environment influencing their welfare. To investigate a commonly occurring human–dog interaction, behavioural and endocrine responses of 12 female beagle dogs were measured before, upon and after the return of a familiar person. Each dog was left by the person in a test arena to which it had been habituated prior to the experiment. Three different treatments were applied when the person returned and each dog experienced all these in a balanced design; the familiar person entered the test arena and 1) initiated physical and verbal contact in a calm and friendly way (PV), 2) there was verbal contact only (V) or, as a ‘control’, 3) the person ignored the dog (C). Interaction continued for 4 min during which the person behaved in a standardized way according to the treatment. Blood samples were collected to investigate oxytocin and cortisol levels. Upon return, oxytocin increased initially, probably because of the dog seeing the person entering the room and walking towards the area where the dog was housed. In treatment PV, where physical contact was applied, elevated levels of oxytocin were observed even after the interaction had ended. Cortisol levels showed a decreasing curve throughout the test, however this decrease was most pronounced in treatment PV, possibly as a consequence of the oxytocin release. Also, dogs in this treatment initiated more physical contact with the familiar person and expressed more lip licking upon reunion. The initial responses to reunion in treatment V were tail wagging and vocalisations. When dogs were ignored upon reunion in treatment C, they could have redirected their approach-behaviour towards an assistant (who was always situated in the room). To conclude, the type of interaction evidently affected the endocrine and behavioural responses of dogs in different ways. The mere return of the familiar person had a positive effect on oxytocin levels and induced contact-seeking behaviour, whereas physical contact was necessary in order to induce a sustained increase in oxytocin levels and to decrease cortisol levels in the period following reunion.