Authors: Giulia Pedretti1,2*, Chiara Canori2, Sarah Marshall-Pescini3, Rupert Palme4, Paola Valsecchi2,1

1University of Parma, Department of Medicine and Surgery, Via Gramsci 14, Parma, 43126, Italy; 2University of Parma, Department of Chemistry, Life Science and Environmental Sustainability, Viale delle Scienze 17/A, 43124, Parma, Italy; 3Domestication Lab, Wolf Science Center, Konrad-Lorenz-Institute for Ethology, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria; 4Unit of Physiology, Pathophysiology and Experimental Endocrinology, Department of Biomedical Sciences, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria

Different facial expressions (i.e., ears flattener, inner brow raiser) and displacement behaviors (i.e., lips licking, yawning, blinking) have been identified both as stress indicators and communicative signals in domestic dog training and scientific literature. The interpretation of dogs’ behavior can be very important during training and performance assessment. However, few studies systematically investigated the nature and functions of such behavioral patterns. Criteria allowing to disentangle behavioral patterns caused by generalized arousal (physiological activation of the organism), from those actively performed as means of communication are their dependence on the presence of a social partner, the so-called “audience effect”. In our studies, we investigated the influence of positive and negative high-arousal situations and the presence of an interspecific (human) and intraspecific (dog) audience, on dogs’ behavioral displays and facial expressions. We exposed dogs to positive anticipation, non-social frustration, and social frustration (with a human or a conspecific) evoking test sessions (food visible through a Plexiglas and made available or denied) and measured pre and post-test salivary cortisol concentrations. Cortisol concentrations did not increase depending on the test condition while in general post-test cortisol was positively associated with pre-test cortisol concentrations. In the first study, displacement behaviors of “head turn” and “sniffing the environment” occurred more in the frustration-evoking situations compared to the positive anticipation and were correlated with pre-test cortisol concentrations, confirming their link with an activation of the stress response. “Ears forward” occurred more in the positive anticipation condition compared to the frustration-evoking conditions, was positively influenced by the presence of an audience, and negatively correlated to the pre-test cortisol concentrations, suggesting it may be a good indicator of dogs’ level of attention. Finally, “ears flattener”, “blink”, “nose lick”, “tail wagging” and “whining” were associated with the presence of a human audience but were not correlated to cortisol concentrations, suggesting a communicative valence of these visual displays. In the second study, when faced with a conspecific audience, dogs assumed a more avoidant attitude, keeping their distance and not looking towards the window, compared to the human test condition. Furthermore, a conspecific audience elicited more facial expressions (ears adductor, ears downward), displacement behaviors (nose lick, lip wipe), tail wagging, whining, and panting compared to the non-social condition. When comparing the two social conditions (frustration human and frustration dog), dogs exhibited more facial expressions (ears adductor, ears rotator), displacement behaviors (nose lick, lip wipe, head turn), panting, and whining when faced with the conspecific. Pre-test cortisol concentrations were positively associated with ears adductor and panting suggesting a link between these behaviors and a higher level of arousal while negatively associated with tail wagging and head turn, suggesting that less aroused dogs were able to express those behaviors. These findings are a first step to systematically testing which subtle cues could be considered communicative signals in domestic dogs. Our results show that different behavioral patterns are flexibly exhibited depending on the audience present, questioning their direct link with stress and suggesting a more complex communicative function.