Translocation effects on regional and local population viability and connectivity.

Translocations and reintroductions aim to improve the viability of isolated populations and promote connectivity for large carnivores. However, there is no established framework for assessing their success. We used the Eurasian lynx (Lynx lynx) in western and central Europe to assess the impact of translocations on the viability of six populations and their interconnectivity. Lynx populations are small and isolated and have low genetic diversity. Population reinforcements have been carried out, but their impact has not been determined. We devised a workflow to evaluate how releasing new individuals affects population extinction probability and connectivity and patch colonization, and to estimate the minimum release population to create a stepping-stone network. To this end, we calibrated a spatially explicit, individual-based model with space use, survival, and reproductive rates observed in the populations and validated it with field data on population growth and expansion from the 1970s to 2020. We ran the model with the observed population structure in 1995-1996 to 2040 in two scenarios, with and without translocations. In both scenarios, most existing populations remained stable in our model for the next 20 years, but had low connectivity. Lynx translocations positively affected viability and connectivity on a population scale but did not increase connectivity between the eastern and western Alps. To create a stepping-stone population that would significantly improve connectivity across the Alps, we conservatively estimated that at least 13 males and 37 females should be released in the Italian southeastern Alps based on the assumption of negligible immigration rates between patches. Concerted transboundary management to improve the future survival of lynx populations in western and central Europe is still needed.