We all hope that our conservation translocations will meet with success, and we expend much time and energy planning for a positive outcome. However, in reality, many translocations fail. Defining what makes a translocation ‘successful’ can be challenging and this difficulty may be magnified when working with cryptic or poorly studied species or when multiple species are involved. Criteria for success must be relevant to the objectives of the translocation, should be measurable and have realistic timeframes for achievement. However, how we evaluate progress against these criteria is highly dependent on our ability to effectively monitor a species, which may be constrained by its behaviour, the release methods or the release environment, including sympatric species. Ineffective monitoring strategies may render some criteria difficult or impractical to evaluate. Finally, poorly defined success criteria may result in apparently successful translocations failing to achieve their stated criteria, or translocations that meet their success criteria but are ultimately doomed to failure.
Here, we discuss the challenges that have been faced with defining and evaluating success for a fauna reconstruction program on Dirk Hartog Island in Western Australia. To date seven species have been translocated to the island, all showing initially promising signs. However, the achievement of success criteria within prescribed timeframes has been mixed and has highlighted deficiencies in how we define and measure success. We discuss how we have adapted to this and how this experience has shaped the way we think about success criteria for future translocations.