An analysis of social play in polecats (Mustelidae) with comments on the form and evolutionary history of the open mouth play face

A description is given of social play in polecats (Mustela putorius L.) based on frame-by-frame analysis of cine film. Social play more closely resembles fighting than any other form of adult behaviour, but biting is inhibited, occupying only 2% of the polecats' time as opposed to 40% in fighting. A metacommunicatory function can be ascribed to behaviour occupying 48% of the time spent in social play; the open mouth play face is displayed for...