Reintroduction as a tool for the recovery of warru (Petrogale lateralis MacDonnell Ranges race) on the Anangu Pitjantjatjara Yankunytjatjara Lands of South Australia.

Abstract

Captive breeding for reintroduction is widely used as a tool for threatened species conservation. While captive populations have been successfully established for many species, the failure rates of subsequent reintroductions have been high. Often this is because managers are required to make reintroduction decisions without adequate knowledge of species biology, and little or no understanding of post-release population dynamics. A captive-breeding for reintroduction programme was initiated in 2007 for warru (black-footed rock-wallaby, Petrogale lateralis MacDonnell Ranges race (MRR)) of the Anangu Pitjantjatjara Yankunytjatjara (APY) Lands of South Australia (SA). A 97-ha predator exclosure (the “warru pintji”) was constructed on the APY Lands in 2010 in which to release captive warru to establish a source population for future releases. This thesis presents five data chapters that examine multiple aspects of the soft-release (release from captivity to a fenced area of natural habitat in comparison to a hard release which is directly to the wild) and long-term reintroduction process, with the broad aim to advance the limited knowledge of warru reintroduction biology and assess reintroduction as a potential recovery tool. Responses to reintroduction and post-release population dynamics were assessed through a 24-month multi-faceted monitoring programme following the release of 16 captive warru. Warru survival rate was 63%. Definitive mortality causes were not determined but their early timing suggested reintroduction-related stress. Blood biochemistry and body mass indicated rapid adaptation to the wild in surviving warru, with maintenance of excellent body condition post-release. This was also evidenced by high female reproductive rates. This work represents the first data on the reintroduction biology of warru. Behaviours post-release were examined using Global Positioning System (GPS) collars in home range studies of seven reintroduced warru. As knowledge of warru home ranges was lacking, GPS collars were also fitted to nine warru within a remnant population to facilitate comparison. Reintroduced warru displayed rapid selection of hill habitat and established home ranges (8.9 ± 5.9ha) with core areas centred about the rocky outcrop. Reintroduced warru displayed lower fidelity to their home ranges compared to remnant warru, likely due to exploratory behaviours and establishment of dominance hierarchies, although none of these behaviours led to dispersal from the release site. Patterns of male/female overlap were similar to the remnant warru population suggesting the formation of a functioning social system post-release. Drinking at supplementary water points was significantly predicted by rainfall and plant moisture content for both reintroduced and remnant warru populations. As limited rainfall during the dry winter on the APY Lands is linked to low juvenile warru survival, the results suggest that provision of supplementary water during the drier winter or drought could alleviate resource pressures for warru. This could potentially increase warru survival chances and thus population persistence. A review of the genetic composition of the three in situ warru populations (New Well, Alalka and Kalka), the two genetic captive groups (1-New Well/Alalka and 2-Kalka), and the broader MRR, was undertaken using 14 microsatellite loci and a 672 base pair sequence of mitochondrial DNA. Captive groups had significantly lower genetic diversity than their wild source populations, increasing the likelihood of inbreeding. While microsatellite data presented significant contemporary genetic differentiation among the in situ populations, there was a lack of phylogeographic structure within mitochondrial haplotypes, suggesting greater historical connectivity across the MRR. Outbreeding depression was therefore predicted to be unlikely, so this thesis recommends that captive warru populations be managed as one genetic group to increase the adaptive potential of future reintroduced groups. These data provide the first phylogenetic analysis for the MRR and highlight the importance of assessing historical, as well as contemporary genetic structure, for threatened species. Population viability analysis using post-release demographic rates predicted that the warru pintji population would exhibit a positive growth rate. Supplementation of the pintji population from captive stock in 2014 and delaying the first removal of a release group for new reintroductions until 2015 will enable larger release groups to be removed. This should increase the probability of successful establishment of the released population. Juvenile recruitment is an important component of successful establishment of a reintroduced warru population and will require intensive monitoring to enable adaptive management, such as the release of additional animals or increased predator control, to be implemented if successful recruitment is not observed. The results of the current study suggest that, in the absence of introduced predators, reintroductions are capable of successfully re-establishing populations of warru. The thesis provides a case study of the reintroduction biology data that can be obtained through appropriate, intensive and targeted monitoring of both reintroduced and remnant populations. The outcomes also highlight the contributions that a long-term soft release can make to assess the suitability of captive breeding for reintroduction as a tool for population recovery. Future monitoring of hard releases of warru to gain comparative reintroduction biology data will ultimately determine the role that reintroduction can play in warru recovery on the APY Lands.