Summer distribution of Caribou, Rangifer tarandus granti, in the Area of the Prudhoe Bay oil field, Alaska, 1990-1994

Abstract

Aerial surveys were conducted within the Prudhoe Bay oil field are in northern Alaska during 1990-1994 to document summer distribution of Caribou (Rangifer tarandus granti). Numbers of Caribou observed per survey ranged from 34 to 13058. When insect activity was moderate to high, more Caribou were observed within the oil field than when insect activity was low. Severe mosquito (Aedes spp.) harassment often resulted in large post-calving aggregations of Caribou in coastal areas. When mosquito harrassment subsided, aggregations often moved inland through the oil field or laterally along the coast. On several occasions, large groups of Caribou (2000-4000 individuals) were observed feeding or bedded down in the central portion of the oil field. Caribou were observed on, and used, oil field gravel pads and roads as insect relief habitat during the mosquito season in late June through mid-July, and also ysed the shade of oil field structures when oestrid flies (Hypoderma tarandi and Cephenomyia trompe) were abundant from mid-July to early August. Five years of observations document that Caribou use habitat within and travel through oil fields during summer periods of high insect activity.