Discrimination between male former group members and unrelated males was tested in 13 males. During tests, each subject lived in a cage connected by tunnels to 2 cages, each housing a stimulus male. Subjects used the tunnels to approach and interact with both stimulus animals. Proximity to the stimulus males, aggressive and non-aggressive contacts and exchange of tongue flicks were recorded. Aggressive contacts were rare. The subjects had significantly more non-aggressive contacts with former group members than with unrelated males but exchanged significantly more tongue flicks with unrelated animals. There was no difference in proximity to either class of stimulus male.