FAIRBANKS - The populations of two of Alaska's largest caribou herds have increased significantly in the past seven years, but numbers in surrounding herds have declined.
State wildlife biologists don't know why the Central Arctic Caribou Herd - the state's third-largest herd - has more than doubled and the Teshekpuk Caribou Herd - the fourth-largest - has similarly increased.
Biologists said the Western Arctic and Porcupine herds, Alaska's largest caribou herds, appear to be decreasing in populations.
Caribou herds are known for fluctuating numbers, and the Central Arctic herd is a prime example. It numbered about 5,000 animals in the early 1970s. The herd grew to 24,000 in the 1980s before declining, then began growing again in the 1990s and has grown ever since to 67,000 animals.