Population viability analysis informs Western Grasswren translocation: Multi-population sourcing of 112 founder individuals needed to meet success criteria

Abstract

Abstract Conservation translocations have become an increasingly popular method to restore or secure vulnerable populations. However, translocations greatly vary in success. The use of population viability analysis (PVA) may increase the likelihood of meeting translocation goals. However, the quality of PVAs to inform translocations is dependent on the availability of ecological data and clear translocation objectives to guide them. Here, we used PVAs to inform the planned conservation translocation of the Western Grasswren (Amytornis textilis textilis) from mainland Shark Bay onto Dirk Hartog Island, Western Australia. A range of translocation scenarios were modelled and scored against success criteria as determined by translocation objectives. Simulations of 20-yr outcomes found that a minimum founder population of 112 individuals meet all success criteria. PVA supported sourcing individuals from 2 subpopulations to maximize genetic diversity. No impact to source populations was detected for the proposed harvest quantities despite conservative estimates of initial source population sizes. Here we demonstrate that creating clear, measurable objectives alongside a PVA lessens ambiguity about which translocation scenarios could be viable. In doing so, we have identified the minimum translocation sizes needed to maintain genetic diversity and population growth, thus increasing the likelihood of translocation success without impacting the source population.