DIET, BODY-SIZE AND THE ENERGY COSTS OF LOCOMOTION IN SALTATORY PRIMATES

We report the energetic costs of locomotion in five nocturnal, saltato ry prosimians. Using data on nightly travel distance, locomotor freque ncies, distance and height change in each locomotor mode, we calculate d absolute and relative costs of locomotion. Locomotion contributes at most 2% to total daily metabolic energy costs, consistent with most e stimates for quadrupedal species. Tarsius, the smallest, has the lowes t absolute and relative cost of locomotion, but the third smallest, Av ahi, has the highest absolute and relative costs of locomotion, follow ed by the largest species, Otolemur crassicaudatus, which incurs parti cularly high costs in upwards-directed locomotion. Lepilemur's costs o f locomotion are maintained at an unexpectedly low level by remarkably short nightly travel distances.