High Grazing Impact, Selectivity, and Local Density of Muskoxen in Central Ellesmere Island, Canadian High Arctic

Abstract

Grazing activities and densities of muskoxen in Sverdrup Pass, Central Ellesmere Island, were investigated by use of an automatic camera monitoring system from May to August, 1987 and by direct observation from March to May 1988. Average seasonal density of muskoxen was 6.4 ± 1.9 (S.E.M.) animals × km⁻² resulting in an average of 48.3 ± 5.1 (S.E.M.) % of available shoots grazed in meadow stands. These figures far surpass previous estimates of density or impact of muskoxen in the High Arctic. It shows that in some high arctic plant communities herbivores can reach high densities and have a high impact, even though aerial survey counts of large areas indicate low average animal densities. Muskoxen selected wet and mesic meadow communities between April and August, except in late June and late July of 1987, when willow herb fields were chosen. In March and early April of 1988 muskoxen grazed valley slopes with little snow cover and little vegetation. In total, 82.8% of the grazing time between 18 May and 18 August 1987, was spent in meadows, despite the fact that these communities covered only 31% of the study area. Muskoxen were therefore highly selective grazers.