Reintroduction of Bridled Nailtail Wallabies Beyond Fences at Scotia Sanctuary – Phase 1

Abstract

Forty male bridled nailtail wallabies Onychogalea fraenata were translocated from an on-site captive breeding compound to two release areas beyond the 8000 ha conservation fences at Scotia Sanctuary (far western New South Wales) in late July 2010. We tested the hypothesis that site fidelity (facilitated by spreading soil laden with female bridled nailtail wallaby odour at the release site) would increase survivorship by restricting animals to Scotia where intensive pest animal control has occurred. Two groups of fifteen animals were fitted with radio collars and released at the two areas (odour-added and odour-free) and monitored intensively for three months. Seven of the bridled nailtail wallabies survived this period, 19 died and four remain unaccounted for. Of the 19 that died, three were killed by introduced red foxes Vulpes vulpes, two by wedge-tailed eagles Aquila audax and one by a dingo/dog Canis lupus dingo. Two bridled nailtail wallabies died from pneumonia. The causes of death for the remaining 11 individuals are unknown. Following their release, 13 bridled nailtail wallabies remained on Scotia whilst the other 13 left the sanctuary (excluding the four that were censored). Those individuals that stayed on Scotia had much higher survival (46%) than the dispersers (8%). This result demonstrates the importance of encouraging the released animals to remain within the area that is subject to intensive predator control. The bridled nailtail wallabies were released at two sites: in an attempt to encourage site-philopatry we added soil laden with bridled nailtail wallaby urine and faeces at one of these sites. Males released here tended to travel less far, and had higher survival, than the males released at the ‘odour-free’ site. We believe the wandering males were searching for mating opportunities. Philopatry may be encouraged and survival increased if females are released with males in future phases of the project. We note that the bridled nailtail wallaby population in Scotia’s 8000 ha feral free area, and also in Scotia’s captive breeding colony, continued to increase during the initial three months of the translocation.