Steep slopes, shallow angles: mountain ungulates create their own topography through movements

Travel is considered to account for a substantial proportion of endothermic species energy expenditure. However, transport costs depend on speed of the animal and slope angle of the terrain. We used biologging data from six ungulate species within the French mountains, combined with mapping data, to examine how these different species reacted to slopes by varying travel speed, and chosen ascent and descent angles, in relation to vectoral dynamic body acceleration (VeDBA; as a proxy for energy expenditure). As predicted by theory and as seen in pumas, animals travelled obliquely so that the angle that any individual experienced was lower than that of the topography. Travel speed affected the VeDBA-based proxy for cost of transport (COT) even though most species moved slower on steeper inclines. Models that considered speed, COT, slope, and habitat type showed clear relationships between COT and slope with variation across habitat types and according to species. Species-specific choice of travel speeds and slope chosen by animals underpins fundamental differences in species physiology and ecology via links in heat production and time spent per altitude. Understanding these interrelations points to the complexity of factors affecting space use by mountain ungulates and is crucial for conservation efforts, especially in fast-changing environments where energy expenditure, temperature changes, and resource accessibility impact population wellbeing.