Demography of bridled nailtail wallabies translocated to the edge of their former range from captive and wild stock

Despite numerous, generally unsuccessful attempts to reintroduce threatened Australian mammals, the factors leading to their failure have not been fully clarified, although predator control would appear to be of paramount importance. An experimental approach was taken in attempting to establish a population of bridled nailtail wallabies in an area of apparently suitable habitat and low fox density, but on the edge of the species’ former range. The 133 wallabies released since late 1996 comprised four groups: captive-bred animals, wild caught from the single remaining wild population, animals that were captive bred and acclimatised at the translocation site in a 10 ha predator-proof enclosure, and animals which had been bred in the enclosure. Survival was highest in those bred in the enclosure and highly variable among captive-bred animals. Survival estimates for wild recruits suggested the population would maintain a positive rate of increase under prevailing environmental conditions. Spotlighting surveys suggested the population had increased to approximately 400 animals by late 1999. Above average rainfall during 1996–1999 and no apparent predation suggests caution in describing the translocation as a success. Ongoing monitoring is critical, because it is uncertain how the population will cope with drought and inevitable predation events, and whether the population will expand and persist outside of limited preferred habitat.