Caribou distribution and group composition associated with construction of the Trans-Alaska pipeline

Abstract

Caribou surveys were conducted periodically along the Trans-Alaska Pipeline haul road on the centra l Arctic Slope between June and November 1975. Mean calf percentage observed in summer was approximately one-third lower than that obtained from concurrent aerial surveys of both the pipeline corridor and adjacent areas; however, fall means were identical. In both summer and early fall, mean latitudes calculated for groups with and without calves along the haul road were more southerly than for the corresponding group types observed through aerial survey. A more detailed regional comparison of survey data revealed corridor-related abnormalities in Caribou distribution and group composition. No Caribou, or relatively low numbers, were observed in the northernmost segment of the pipeline corridor near Prudhoe Bay, and calf percentages in summer were consistently lower for each of four arbitrarily established regions of the haul road than expected on the basis of aerial survey results; fall calf percentages did not differ appreciably. Mean group size was generally lower along the haul road than for comparable areas to the east and west. Responses of Caribou to the pipeline corridor in general, and of cows and calves in particular, are discussed in relation to inherent avoidance tendencies as modified seasonally by terrain group dominance, and human activity.