The bush dog, Speothos venaticus, is a rare forest-dwelling South American canid. Social behaviour of a captive pack of three adult males and three adult females was observed over four years in a large enclosure. The dogs appeared to be compulsively sociable, sleeping in close physical contact, travelling together in single file, and feeding communally with minimal aggression. An alpha pair was dominant, but there was no clear hierarchy within the pack as a whole. There were, however, separate male and female hierarchies. The pack engaged in various communal behaviours, including greeting ceremonies in which individuals mutually submitted to one another. All dogs urine marked frequently, both sexes adopting postures to direct urine upwards and to soak their fur in odour. Only the alpha female bred successfully, and all other group members carried and guarded the young. These observations are discussed in the contexts of canid social behaviour and the breeding in captivity of this endangered species.