ECOLOGY OF WOLVES IN RELATION TO A MIGRATORY CARIBOU HERD IN NORTHWEST ALASKA

There is a paucity of data concerning wolf (Canis lupus) demography, m ovement patterns, and predation characteristics in relation to migrato ry caribou (Rangifer tarandus granti). Consequently, during 1987 throu gh 1992, we studied wolves and the Western Arctic Caribou Herd in nort hwestern Alaska. We captured and radio collared 96 wolves in 19 packs and relocated them ion 1,830 occasions. Wolf packs usually did not fol low migratory caribou but maintained year-round resident territories t hat averaged 1,868 km(2). However, during years when caribou were abse nt and moose (Alces alces) densities were low, up to 17% of the radio- marked wolf packs followed migratory caribou and then returned to thei r original territory for denning. Radio-collared wolves (n = 21) dispe rsed primarily during April through September. Spring wolf densities i ncreased from 2.7 to 4.4 wolves/1,000 km(2) during 1987 through 1990, and then declined to 1.5 wolves/1,000 km(2) following a rabies epizoot ic. Annual wolf survival rates averaged 0.552 (rang = 0.464-0.656). An nual survival during 1990-91 and 1991-92 was lower than other years du e to a rabies epizootic. Overall, hunting was the main cause of death (69%) for wolves (n = 52). Most (63%) mortality occurred during Decemb er through March when snow cover permitted wolf hunting from snowmobil es. Caribou and moose composed 51 and 42%, respectively, of the kills observed during the study; 59% of caribou and 64% of moose kills were adults. Ungulate kills averaged 4.6/wolf/100 days and provided 5.3 kg of available food/wolf/day. In northwest Alaska, caribou were the prin cipal prey when present within areas by wolves. However, when caribou densities were <200/1,000 km(2), wolves switched to preying on residen t moose. Wolves within the range of the Western Arctic Caribou Herd ki lled 6-7% of this caribou population annually. Caribou left wolf pack territories during winter, and wolves switched to preying on moose for approximately 4 months of each year. Wolves killed from 11 to 14% of the moose population annually. Wolf densities were limited by hunting and trapping, and wolf predation at levels found in 1987-91 did not st rongly limit caribou population growth. However, existing wolf populat ions may be able to regulate local, low-density moose populations that have become established during the past 40 years.