The influence of insects on the distribution, microhabitat choice, and behaviour of the Burwash caribou herd

Abstract

This study examined the influence of insects (mosquitoes and oestrids) on the distribution, microhabitat choice, and behavior of a population of mountain caribou. The study was conducted in the Burwash area of southwestern Yukon Territory during the summers of 1982 and 1983. Mosquito density, the presence or absence of oestrids, and the distribution, microhabitat use, and insect-avoidance behavior of the caribou were observed. Seasonal activity budgets for caribou were calculated. Mosquitoes became active in mid-June. Activity decreased with altitude, and at the highest altitudes (2000 m) the number of mosquitoes was negligible. Snow patches and exposed windy ridges had fewer mosquitoes than did open tundra. The oestrid season began in late June and lasted until early August. Oestrids were widespread throughout the study area and were present in all microhabitats. Caribou reduced harassment by mosquitoes by their altitudinal movements and use of microhabitat. Oestrids influenced activity budgets of caribou, acting to decrease feeding and resting time and to increase the time spent standing and moving.