LAUSR

Significance A replicated management experiment was conducted across >90,000 km2 to test recovery options for woodland caribou, a species that was functionally extirpated from the contiguous United States in March 2018. Recovery options were reductions of predators, reductions of overabundant prey, translocations, and creating fenced refuges from predators. Population growth was strongest where multiple recovery options were applied simultaneously. This adaptive management study was one of the largest predator-prey manipulations ever conducted and provided positive results for this endangered North American ungulate. Adaptive management is a powerful means of learning about complex ecosystems, but is rarely used for recovering endangered species. Here, we demonstrate how it can benefit woodland caribou, which became the first large mammal extirpated from the contiguous United States in recent history. The continental scale of forest alteration and extended time needed for forest recovery means that relying only on habitat protection and restoration will likely fail. Therefore, population management is also needed as an emergency measure to avoid further extirpation. Reductions of predators and overabundant prey, translocations, and creating safe havens have been applied in a design covering >90,000 km2. Combinations of treatments that increased multiple vital rates produced the highest population growth. Moreover, the degree of ecosystem alteration did not influence this pattern. By coordinating recovery involving scientists, governments, and First Nations, treatments were applied across vast scales to benefit this iconic species.