Do looks matter? Investigating facial expressions and intraspecific communication across different dog morphotypes

Brachycephalic dogs gained great popularity in recent years, however the extreme conformation (e.g., wide eyes, flat nose, round heads, short tails) characterizing some breeds raised concerns about the effectiveness of facial signals in these dogs. These features might create challenges for an effective intraspecific communication and potentially lead to misunderstandings during intraspecific interactions. This study aimed to investigate potential differences in behavioural displays during intraspecific approaches between dogs of different morphotypes: hunting dogs and shepherd dogs (mesocephalic morphotype) and small companion molossoids and guard molossoids (brachycephalic morphotype). Fourteen brachycephalic dogs and sixteen mesocephalic dogs were tested. We predicted that mesocephalic and brachycephalic would express facial signals at different extent and that if brachycephalic dog facial signaling is impaired by their facial conformation it could elicit different responses in the opponent dog. Contrary to our predictions, no behavioural differences were found between brachycephalic and mesocephalic breeds, suggesting that extreme conformation of brachycephalic dogs has not drastically altered their communicative abilities. Further results showed that the “tongue flicking” behaviour, previously suggested to function as an early warning in conflicted/aggressions-related contexts was performed more by mesocephalic TESTED DOGS when the DOG STIMULUS was a brachycephalic dog, suggesting that this morphotype can elicit intense and ambiguous response in mesocephalic dogs. Conversely, the “bow” behaviour, a stereotyped cue consistently found in canids intraspecific social contexts, was expressed more by the mesocephalic TESTED DOG towards other mesocephalic approaching DOG STIMULI. Different behavioural patterns associated to the specific breed types tested emerged: shepherd dogs showed higher alertness and dog orientation, hunting dogs barked more, guard molossoids showed calm vigilance and small companion molossoids were more avoidant in regards of the dog approaching them. The present study is the first aimed to examine if the brachycephalic morphotype influences dogs’ intraspecific communication and due to the limited number of dogs tested further experimental evidences are needed. Nevertheless, it appears that brachycephalic dogs are perceived differently by non-brachycephalic ones and these results could provide valuable insights for researchers, breeders and dog trainers.