The size of a large caribou herd in Alaska's Arctic region has dropped by more 50 percent over the last three years, and researchers who have tentatively ruled out hunting and predation as significant factors for the decline are trying to determine why.
The state's Central Arctic herd, which roams an area of north-central Alaska about the size of Ohio, hit a peak of about 70,000 caribou in 2010.
It fell to 50,000 in 2013. That year, spring arrived late, meaning caribou had to trudge through snow later than usual at a time when their bodies are already stressed and not getting the grasses they need for nutrition.
Surveys by the Alaska Department of Fish and Game...