Responses of Caribou to Overflights by Low-Altitude Jet Aircraft

Maier, Julie; Murphy, Stephen; White, Robert; Smith, Michael

Military training exercises have increased in Alaska in recent years, and the possible effects of low-altitude overflights on wildlife such as barren-ground caribou (Rangifer tarandus) have caused concern among northern residents and resource agencies. We evaluated the effects of overflights by low-altitude, subsonic jet aircraft by U.S. Air Force (USAF) A-10, F-15, and F-16 jets on daily activity and movements of free-ranging female caribou. This study was conducted on caribou of the Delta Caribou Herd in interior Alaska during each of 3 seasons in 1991: late winter, postcalving, and insect harassment. Noise levels experienced by caribou were measured with Animal Noise Monitors (ANMs) attached to radiocollars. Caribou subjected to overflights in late winter interrupted resting bouts and consequently engaged in a greater number of resting bouts than caribou not subjected to overflights (P = 0.05). Caribou subjected to overflights during postcalving were more active (P = 0.03) and moved farther (P = 0.01) than did caribou not subjected to overflights. Caribou subjected to overflights during the insect season responded by becoming more active (P = 0.01). Responses of caribou to aircraft were mild in late winter, intermediate in the insect season, and strongest during postcalving. We conclude that females with young exhibit the most sensitive response to aircraft disturbance. Accordingly, military training exercises should be curtailed in areas where caribou are concentrated during calving and postcalving.

Responses of Caribou to Overflights by Low-Altitude Jet Aircraft

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