A review of New Zealand native frog translocations: lessons learned and future priorities

Translocations are becoming increasingly common although the effectiveness of this conservation tool for amphibians is highly variable. We reviewed ten translocations of Leiopelma frogs occurring between 1924 and 2016. Data were gathered on factors which may have influenced translocation outcomes. Results at each location were measured against an established four-step framework for stages of success: survival of individuals, reproduction, population growth, and population viability. Three conservation translocations and two mitigation translocations were considered to have failed, indicated by no or low survival of founders or lack of evidence of reproduction within a reasonable timeframe. Causes of failure include invasive predators at the release site, small founder numbers, homing, and poor habitat quality. The remaining five translocations were considered either successful (meeting all four stages of success), or on the road to success (meeting at least the first two stages of success). Successful translocations included predator control, total release of more than 70 founders, and in some cases adaptive management to address management decisions over time. Our findings emphasise the need for long-term post-release monitoring (> 25 years) to determine translocation success for K-selected species. Better, cost-effective, methods for monitoring population growth and population viability are required for Leiopelma frogs. Improvements could be made in open access reporting of methods and decision-making, disease risk analysis and stakeholder engagement. Further, improving our knowledge of what makes high quality Leiopelma habitat would help to objectively assess potential future translocation sites. Future translocations should consider the impacts of predicted global climate change; assisted migration may be required in the future. Translocations are a risky conservation strategy, so should only be undertaken with good cause, quality planning, and sufficient long-term resources for monitoring and management. Any future translocations for Leiopelma, whether motivated by conservation or mitigation, should follow best practice guidelines and use evidence-based decision-making to maximise outcomes.