EFFECTS OF WEATHER AND PARASITIC INSECTS ON BEHAVIOR AND GROUP-DYNAMICS OF CARIBOU OF THE DELTA HERD, ALASKA

The influence of weather and parasitic insects on the behavior and gro up dynamics of caribou (Rangifer tarandus) of the Delta Herd in the no rth-central Alaska Range was investigated. Data on weather, insect abu ndance, and caribou behavior were collected during summer in 1994 and 1995. High ambient temperature had the greatest influence on activity budgets and rates of change in activity of caribou. In the insect seas on, rates of activity changes and standing increased and feeding decre ased with high temperature. Rates of activity changes and moving incre ased and feeding decreased with high temperature, even in the absence of insects. Caribou decreased feeding and increased standing in the pr esence of oestrid flies, and increased the rate of activity changes in the presence of mosquitoes and oestrid flies. Weather, especially hig h temperature, and parasitic insects, particularly oestrid flies, affe cted caribou mainly by decreasing foraging opportunities and increasin g energy-expending activities.