Demography of bridled nailtail wallabies translocated to the edge of theirformer 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 ful ly clarified, although predator control would appear to be of paramount imp ortance. An experimental approach was taken in attempting to establish a po pulation of bridled nailtail wallabies ih an area of apparently suitable ha bitat and low fox density, but on the edge of the species' former range. Th e 133 wallabies released since late 1996 comprised four groups captive-bred animals, wild caught from the single remaining wild population, animals th at 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 am ong captive-bred animals. Survival estimates for wild recruits suggested th e population would maintain a positive rate of increase under prevailing en vironmental conditions. Spotlighting surveys suggested the population had i ncreased to approximately 400 animals by late 1999. Above average rainfall during 1996-1999 and no apparent predation suggests caution in describing t he translocation as a success. Ongoing monitoring is critical, because it A uncertain ho v the population will cope with drought and inevitable predat ion events, and whether the population will expand and persist outside of l imited preferred habitat. (C) 2001 Elsevier Science Ltd. All rights reserve d.