HANNA, JB*; GRIFFIN, TM; Duke University; Duke University: Climbing energetics in primates: effects of body size
Non-human primates move in a three-dimensional environment, but little is known about the physiological demands of climbing. In this study, we examined the metabolic power of climbing in non-human primates spanning more than an 8-fold range in mass. We also examined the vertical climbing efficiency in non-human primates because one can readily and unambiguously measure the minimum rate of performing work against gravity. The rate of oxygen consumption (VO2) was measured at rest and during climbing in 5 species of primates ranging in body mass from 0.160-1.35kg: Loris tardigradus (LT), Cheirogaleus medius, Nycticebus pygmaeus, Saimiri boliviensis, and Eulemur mongoz (EM). Animals were trained to climb a vertical rope treadmill at their maximum sustainable speed while enclosed in a Plexiglas chamber. VO2 was measured during 10-20 minutes of steady-state climbing. We calculated the cost of transport (COT) and compared this to the predicted value for level locomotion by primates using the regression equation from Taylor et al. (1982). Results show that: 1) gross COT decreased with body size, although not significantly (p = 0.15; range=133-109 J kg-1 m-1 for the smallest (LT, 0.160kg) and largest (EM, 1.35kg) animals, respectively), 2) gross climbing COT was similar to that predicted on the level for small primates (<0.5kg) and nearly double that predicted for the two large animals, and 3) net climbing efficiency did not vary significantly with size (p = 0.53; mean net efficiency = 13.8%). These data indicate that the mass-specific COT for climbing does not decrease with body size as much as predicted for level locomotion. The similar net climbing efficiencies across size suggest that mechanical power output to lift the body against gravity is the primary determinant of the metabolic power required for climbing. Support from a NSF GRF, NSF DIG (BCS-04-52631), SEB traveling fellowship, and NIH grants P40-RR001254 & AR051672.
