Predicting Late Winter Distribution of Muskoxen Using an Index of Terrain Ruggedness

Abstract

We tested the hypothesis that occurrence of rugged terrain would affect distribution patterns of muskoxen (Ovibos moschatus) in late winter through expected higher availability of forage. Indices of terrain ruggedness (TRI) based on contour characteristics from topographical maps were found to be correlated with occurrence of muskoxen in late winter 1982–1990 in northeastern Alaska. Rugged terrain (TRI > 2.5) constituted less than half of the study area, but contained 83% of all muskoxen observed during 1982–1990. Occurrence of rugged terrain partly explained differences in density of muskox among 12 major drainages in the study area. Within 7 of 8 drainages having >30% rugged quadrats, density of muskoxen was correlated to terrain ruggedness. The study corresponds well with studies of snow characteristics, terrain ruggedness and forage availability. The results indicate, that availability of rugged terrain likely affects distribution patterns of muskox by influencing local vegetation and snow characteristics. Analysis of terrain structure may thus in combination with data on snow and vegetation patterns improve our understanding of distribution patterns of this arctic grazer during winter.