They exhibit a complex social system, which varies somewhat according to the type habitat in which they live. The basic social unit consists of 2 to 7 adults (typically 5 to 7) – 2 or 3 adult males and 3 or 4 adult females. Group members share a tree hollow in which they build a spherical or bowl-shaped nest of eucalpyt leaves, but they generally forage alone at night. Group membership is closed to outsiders unless a vacancy is created by the death of a member. The dominant male in each group marks other group members with secretions from his head and chest scent glands. There are a variety of calls, including a loud bark or ‘yip’, and a rolling ‘starter motor’ anger call. Juveniles make a hiss when threatened, and will be assisted by any adult member of the same group. They avoid activity in very cold, wet weather by entering a state of torpor, or remaining huddled together in the nest.