Scotia Sanctuary, owned and managed by the Australian Wildlife Conservancy, is a 65,000 ha wildlife sanctuary in western New South Wales. Two 4,000 ha feral predator-free exclosures have been established on the site, with each supporting populations of several reintroduced locally extinct mammal species. Populations of reintroduced mammals are free-ranging within predator exclosures and entirely dependent on their own foraging for sustenance. Population size of each species is estimated annually, with many exhibiting classic boom-bust cycles. This presentation examines whether seasonal conditions, particularly rainfall, are the overriding factor behind the population dynamics and health of these reintroduced species (size of population, condition of animals, breeding rate), focusing on the burrowing bettong Bettongia lesueur. Management intervention of reintroduced species within large fenced exclosures is not a concern where there is evidence of self-regulation by resource limitation.