These are probably regular Barren Ground caribou Rangifer tarandas granti - the species occuring west of the MacKenzie River and well into Alaska? Definitely not the Peary variety Rangifer t. pearyi?
These animals are descended from a herd located on Adak Island in the Aleutian Islands. The Adak herd was established in the 1940's from Barren-ground Caribou brought in from mainland Alaska to serve as an emergency food source and provide recreational hunting opportunities for the island residents. While most of the introduced Caribou where native, wild Caribou...a few domestic Reindeer were also in the mix. These animals likely have genes from both native Alaskan animals and Eurasian Reindeer. In Alaska domesticated Reindeer herds can be found on the Seward Peninsula, Fairbanks, and Palmer. I would not be surprised if small herds existed on other Aleutian Islands. A feral population exists on Kodiak Island as well.