Muskox-Caribou Summer Range Relations on Banks Island, N.W.T.

Abstract

The use of food and space by muskoxen (Ovibos moschatus) and Peary caribou (Rangifer tarandus pearyi) in north-central Banks Island was studied in summer 1973 to ascertain whether interspecific competition was occurring. The distribution and dispersion of the two ungulates overlapped only negligibly, and their preferred habitats and diets were correspondingly different. Muskoxen foraged mainly in wet habitats, where they ate almost exclusively lush sedges (Carex stans), supplemented by grasses and willows (Salix spp.). Caribou were concentrated in sparsely vegetated uplands and ate moderate amounts of small sedges (Carex spp.), grasses, willows, and milk-vetch (Astragalus alpinus). Measurements of carcass fat, marrow fat, and rates of production and survival of young indicated that both ungulates were in good physical condition. We concluded that competition was not occurring. J. WILDL. MANAGE. 40(1):151-162 We report here a study to determine whether muskoxen and caribou were competing for food or space on their summer range in north-central Banks Island, N.W.T. The study was made in summer 1973 after Inuit hunters commented in 1972 on a decline in the numbers and physical condition of caribou shot for meat in southern Banks Island, which, they suggested, might have resulted from competition between muskoxen and caribou in the north of the island during the preceding summer (L. Bouckhout 1972, unpublished report, N.W.T. Game Manage. Div., Yellowknife). Following Miller (1967:6), we defined interspecific competition as the active demand by members of two or more species at the same trophic level for a resource or requirement that is actually or potentially limiting. We recognized the customary distinction between competition through interference and exploitation (Elton and Miller 1954) and acknowledged that competition may be non-reciprocal in the sense of Davis (1952). Competition is, of course, a process, (Milne 1961:56), and processes are notoriously difficult to study in the field. We therefore sought evidence of the results of competition between muskoxen and caribou, as well as the process itself, in the condition of their range, their use of food and space, their behavior, and their physical condition. Each of these classes of evidence may be ambiguous when viewed in isolation since they may reflect processes other than interspecific competition; when considered in combination and in the context of a specific field study, however, the chances of serious misinterpretation are remote. We thank LGL Ltd., Environmental Research Associates (Edmonton), and the Game Management Division of the Government of the Northwest Territories for financial and logistical support and for permission to publish our results. The Canadian Wildlife Service (Edmonton) kindly 1 Present address: Department of Anthropology, University of Otago, Box 56, Dunedin, New Zealand. 2 Present address: Environmental Sciences Centre (Kananaskis), The University of Calgary, Calgary, Alberta T2N 1N4. 3Present address: Faculty of Agriculture and Forestry, Department of Plant Science, The University of Alberta, Edmonton T6G 2E1. J. Wildl. Manage. 40 (1):1976 151 This content downloaded from 157.55.39.123 on Mon, 18 Jul 2016 05:39:45 UTC All use subject to http://about.jstor.org/terms 152 MUSKOX-CARIBOU RANGE RELATIONS * Wilkinson et al.