HABITAT USE BY THE PORCUPINE CARIBOU HERD DURING PREDICTED INSECT HARASSMENT

Harassment of female caribou (Rangifer tarandus) by insects may negatively affect the cows' energy balance during the critical post-calving and lactation period, and certain habitats may provide relief from such harassment. Consequently, we tracked adult, female caribou from the Porcupine Caribou Herd (PCH) by satellite between 25 June and 31 July 1985-89 to determine their habitat preferences during periods of predicted harassment by insects, primarily mosquitoes (Culicidae). When insect harassment was predicted (ambient temperatures greater-than-or-equal-to 13 C and winds <6 m/sec) dry prostrate dwarf scrub vegetation type was preferred by caribou. Caribou used areas of this vegetation type on ridgetops in the foothills and mountains of the Brooks Range and on elevated sites of the coastal plain, as well as areas adjacent to the Beaufort Sea coast to gain relief from mosquitoes. Unlike the caribou in the adjacent Central Arctic Herd, caribou in this sample of the PCH did not show a strong tendency to move to the coastline at the onset of predicted harassment. However, observations of movements of unmarked animals during survey flights indicated that segments of the herd often follow the coastline while moving across the coastal plain of the Arctic National Wildlife Refuge (ANWR) in july. Our findings are only an initial step toward recommendations of habitat mitigation if the coastal plain of the ANWR is opened to petroleum development. Studies that address the interactions between foraging opportunities and insect densities at potential relief sites are necessary to determine consequences to the population if access to relief habitat is restricted.