The partner preferences of a captive group of red-necked wallabies (Macropus rufogriseus banksianus) during playfights were determined and the patterns of social relations formed compared to those in other social contexts. Wallabies preferred play-partners of the same sex and of similar age and dominance status. Young males were most likely to initiate play. Females engaged in play almost exclusively with subadult males and, in particular, their male offspring. Play between females was not recorded. In play between males from different age classes, initiation and termination was independent of age. Termination was dependent on who initiated the interaction: initiators were less likely to terminate playfights than were recipients. Wallabies that had recently vacated the pouch were not the focus of social play in the colony.

Agonistic interactions also occurred most often between wallabies of the same sex and similar age and dominance but older males were most likely to initiate interactions. Initiation and termination of agonistic interactions was age-dependent: older wallabies almost always initiated and won encounters with younger partners. There was no correlation among male dyads between their rates of play and agonistic encounters, dominance reversals were more common in play than in agonism, and the patterns of wins and losses in play and agonism were not correlated. There was some suggestive, but inconclusive evidence that the proportion of time males spent in close proximity at food and water troughs was positively correlated with their rates of play and negatively with their rates of agonistic interactions. There was also some evidence that males that played together often had more frequent affiliative interactions than those that did not. However, there was no correlation between rate of play by males and the proportion of time they spent resting together. These results suggest that the function of social play in the wallabies was motor training and not socialization. In addition, they indicate that play and agonism are causally-distinct categories of behaviour. Based on this interpretation, the relationship between play and serious fighting in macropods and in eutherian mammals is discussed.