Ungulate movement in an extreme seasonal environment: Year-round movement patterns of high-arctic muskoxen

Abstract

Detailed knowledge on movement behaviour of free-ranging muskoxen Ovibos moschatus is currently lacking. Quantifying variation in individual movement and the variables driving such patterns is important to understand how they meet their basic requirements and to inform management. Because muskoxen exist in nutrient-poor systems with extreme climatic and seasonal variability, individual movement patterns are expected to be largely dependent on environmental conditions and the seasonal variation therein. We analysed high-resolution location data of 14 adult female muskoxen roaming around Zackenberg in northeast Greenland (74°28′N, 20°34′W). We assessed the relative importance (Akaike variable weights) of multiple extrinsic conditions in explaining variation in hourly speed, turning angles, and activity. We found that time of day, ambient temperature, and land cover types were the most important covariates explaining variation in fine-scale movement and activity patterns throughout the year. Movement speeds were consistently lower in land cover types with more dense vegetation. Speed of movement was positively correlated with ambient temperature when the days were long, while negatively related with temperature in periods with few or no hours of daylight. Diurnal peaks in movement and activity patterns were observed most of the year (including mid-winter months with 24-h darkness), except during high-summer (24-h of daylight), when individual movement and activity remained continuously high. The topographic variation (elevation and slope) explained only a small part of the variation in muskox movement patterns in the areas where the muskoxen were observed. Analyses of displacement patterns revealed a mixture of movement behaviours. We conclude that muskoxen in high-arctic Greenland adopt a largely nomadic movement behaviour, but do so within a rather small geographical area (app. 5000 km2), and that their movement and activity patterns are largely directed at finding suitable foraging patches and avoiding cold-stress during harsh winter weather.