Ecological investigations of the tundra Ecological investigations of the tundra biome in the Prudhoe Bay region, Alaska . ecologicalinvest00brow Year: 1975 159 WINDSPEED n hr'^ /mi h 40/25|— -1 1 km hr' /mi hr' 3 2/20 14/15 - 16/10 8/5 — Air in shade, at 20 cm above ground Wind speed-km hr range, at 100 cm above ground Harassment ^ I Severe T Moderate None Ambient temperature Fig. 4 Relationship of intensity of insect fiarassment on caribou with ambient temperature and wind speed. fronn a variety of individual behavior responses, including tail wagging, ear flicking, head an
Ecological investigations of the tundra Ecological investigations of the tundra biome in the Prudhoe Bay region, Alaska . ecologicalinvest00brow Year: 1975 159 WINDSPEED n hr'^ /mi h 40/25|— -1 1 km hr' /mi hr' 3 2/20 14/15 - 16/10 8/5 — Air in shade, at 20 cm above ground Wind speed-km hr range, at 100 cm above ground Harassment ^ I Severe T Moderate None Ambient temperature Fig. 4 Relationship of intensity of insect fiarassment on caribou with ambient temperature and wind speed. fronn a variety of individual behavior responses, including tail wagging, ear flicking, head and body shaking, twitching, shuddering, leaping, and bounding, as described by Thomson (1971, 1973). Mosquitos (Aides spp) became active, and the first signs of caribou harassment apparent, as shade air temperature increased above 6°C under still air conditions. With increasing tem- perature, mosquito harassment of caribou be- came progressively greater, as did the mosquitos' tolerance for wind. At shade air temperatures of over 13°C, usually on warm, sunny days, warble flies (Oedemageon tarandi) were observed to be active around caribou herds, causing avoidance responses typical of severe harassment. This relationship between intensity of insect harass- ment with ambient temperature and wind strength was quantified for the Prudhoe Bay area through frequent field recordings (Fig. 4). The regularity of the relationship made it possi- ble to predict the degree of harassment from prevailing weather conditions on any day. Unfortunately, the continuous data on air temperature and wind speeds at the small Prud- hoe Bay meteorological station did not corre- spond to the same parameters measured on the field, because wind speed near the ground was not measured, and because local site variations accounted for a considerable variation in tem- perature. However, as an approximate guide, if a maximum daily temperature of °C or over was recorded, a day of moderate insect harass- me
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