Reintroduction versus translocation: an experimental comparison of conservation techniques using bilbies (Macrotis lagotis) in South Australia
Reintroductions and translocations have been used to re-establish species in areas where they have become locally extinct. The relative merits of these conservation techniques have been controversial and rarely tested. Reintroduced captive-bred animals may be lacking in survival skills required for foraging and predator avoidance. Whereas translocated wild-born animals may have survival skills relevant for their home site, but must adapt to a new environment. Bilbies are one of a suite of mammalian species that have been decimated in arid Australia since European settlement. Formerly widespread throughout continental Australia, they now occur in less than 20% of their former range. Recently, bilbies have been re-established at several sites where they had become locally extinct. We compared dispersal, movement patterns following establishment, and survival of captive-bred bilbies (reintroduced), wild-born bilbies moved from another site (translocated) and wild-born bilbies within an established population (control) at Arid Recovery in central South Australia. All newly released bilbies exhibited an initial dispersal and exploration period. Translocated bilbies quickly established themselves within a few days, and thereafter displayed similar movement patterns and survival to resident bilbies. Reintroduced bilbies dispersed further than translocated animals, and were still roaming widely two weeks post-release. Initial loss of weight and condition following release was evident in both release groups, with adult males suffering significantly greater weight loss than females or subadults. Mortality in the reintroduced group was considerably higher than the translocated and control groups. Captive-bred bilbies may benefit from pre-release training to provide them with survival skills, and translocation between established wild populations is the preferred approach to future management of these small, isolated, re-established populations.