PARASITIC INSECT ABUNDANCE AND MICROCLIMATE OF GRAVEL PADS AND TUNDRAWITHIN THE PRUDHOE BAY OIL-FIELD, ALASKA, IN RELATION TO USE BY CARIBOU, RANGIFER-TARANDUS-GRANTI

During the post-calving period (late June-early August), Caribou (Rang ifer tarandus granti) movements, distribution, and behavior are signif icantly influenced by harassment from parasitic insects such as mosqui toes (Aedes spp.) and oestrids (Warble Fly [Hypoderma tarandi] and Nos e Bot Fly [Cephenomyia trompe]). A number of studies have mentioned th at Caribou use oil field infrastructure features such as gravel pads a nd roadbeds during insect harassment but there has been no effort to q uantify factors contributing to this behavior. During 1992 and 1993 pa rasitic insect abundance and several weather parameters were measured on active and inactive gravel drilling pads, and undisturbed adjacent tundra in the Prudhoe Bay oil field, Alaska, in an effort to explain u se of these man-made structures by Caribou. Ambient air temperatures w ere lower on gravel pads than adjacent tundra at inactive pads but not at active pad sites. Wind velocities were higher on inactive and acti ve pads than on adjacent tundra. Mosquitos were more abundant on tundr a than gravel pads at both active and inactive sites. Mosquito abundan ce was positively correlated with temperature and negatively correlate d with wind velocity and relative humidity at both inactive and active gravel pads. During periods of high insect harassment Caribou were ob served using both active and inactive gravel pads.