For almost 60 years, the predator-prey relationship between wolves and moose on Isle Royale, a small island in the northwest part of Lake Superior in Michigan, US, has been the focus of ongoing research. In recent years, however, the number of wolves on the island has ＿＿（21）＿＿ due to inbreeding; there now remain only two individuals—one male and one female—on the 200-square-mile island. This has led to 22 growth of the island's moose herds, which graze extensively in the national park's surrounding forest. The situation has ＿＿（23）＿＿ debate about whether to attempt a genetic rescue of the wolf population or ＿＿（24）＿＿ any intervention and allow extinction. On September 22, the US National Park Service (NPS) announced its decision to ＿＿（25）＿＿ the wolf population. By the end of October, six wolves from Michigan and Minnesota will be airlifted to Isle Royale by the NPS.