Malleefowl (Leipoa ocellata) are in decline across their range. Previous studies have found that the survival rate of young Malleefowl is low, the single greatest cause of mortality being predation by the introduced Red Fox (Vulpes vulpes). Many of these studies, particularly those in New South Wales (NSW), were conducted in habitats that were heavily modified by fire, exotic herbivores or plant harvesting. In this paper, we examine the survival of Malleefowl in relatively undisturbed mallee habitats within two conservation reserves in South Australia (SA). Both reserves were long unburnt and free of large exotic herbivores, but differed greatly in understorey structure. Fifteen young captive-reared Malleefowl were released into each reserve. In all, 70% of these individuals were dead within 40 days. Fox predation was the prime cause of mortality, accounting for at least 30%, and perhaps as much as 96%, of all deaths. The extent and causes of mortality were similar in the two reserves. The overall level of Malleefowl survival was (1) better than that recorded in more disturbed habitat in NSW in the absence of any Fox control, but (2) substantially less than that in NSW after widespread Fox control was implemented. This study indicates that Malleefowl in SA are subject to significant levels of Fox predation, even in relatively undisturbed habitats. Also, for the two mallee habitats examined, evidence suggests that understorey structure had no influence on the degree of predation. Available data indicate that during the past two decades Malleefowl populations in SA have declined at about the same rate as those in NSW. Current densities in SA are typically about one-quarter of what they were 15 years ago. We conclude that habitat integrity and structure have little effect on the interaction between Foxes and Malleefowl, and suggest that Malleefowl populations across Australia are threatened by Foxes, placing the species at substantial risk of extinction.