• Canis familiaris
• Canis lupus
• facial expressions
• play behaviour
• play bow
• relaxed open mouth
• threatening faces

This thesis explores the communicative abilities and play behaviour of wolves and dogs, shedding light on how artificial selection by humans has shaped their interactions. The study focuses on playful communicative tactics, play fighting, and visual signals in these animals.
The dog (Canis familiaris) serves as an excellent model for studying communicative versatility, being the first domesticated animal separated from its wild relative, the wolf, around 23,000 years ago.
Play fighting is a central behavioral domain, as it involves elements from “serious contexts”, such as the aggressive one. Effective communication is crucial during play fighting to prevent misunderstandings and make the activity rewarding. Identifiable play signals (e.g., laughter in humans and great apes, play bow and relaxed open mouth in canids) play a role in facilitating playful interactions.
Chapter 2 compares playful modalities between Czechoslovakian Wolfdogs (CWDs) and grey wolves, suggesting a possible impact of domestication. While both wolves and dogs engage in adult play, wolves tend to play more aggressively and with shorter sessions to prevent escalation. Despite these differences, the play ethogram of dogs and wolves are nearly overlapping.
Chapter 3 delves into the visual communicative systems during play and real fighting. Previous studies have provided only qualitative descriptions of these expressions, but this research offers a quantitative analysis of muscle activation, revealing distinct facial expressions associated with play and aggression.
Chapter 4 examines the functions of dogs' play signals, focusing on the Czechoslovakian Wolfdog to minimize the impact of artificial selection. The relaxed open mouth is considered a ritualized version of the play bite and likely helps manage play sessions, although empirical evidence has been lacking. The play bow, on the other hand, has sparked debates about its characteristics and functions, with some suggesting a metacommunicative role and others questioning its status as a signal. The study employs various methodologies, including k-means clustering analysis, survival analysis, and Linear Mixed Models, to demonstrate the ritualized nature of the relaxed open mouth in Czechoslovakian Wolfdogs, clarify the communicative role of the play bow, and assess their impact on play session management.
In conclusion, this research explores the communicative tactics and play behaviour in wolves and dogs, shedding light on the impact of domestication on their interactions and the role of visual signals in facilitating smooth play sessions.