Energy expenditure during level locomotion in large desert ungulates: the one-humped camel and the domestic donkey

This study sought to quantify the rate of energy expenditure (     ), the total cost of transport (COT_tot) and the net cost of transport (COT_net) in camels Camelus dromedaries and donkeys Equus asinus during level locomotion.     of camels and domestic donkeys were measured at exercise speeds between 0 and 4.17 m s⁻¹. Resting     for camels was significantly ( P <0.05) lower than predicted, while donkeys exhibited resting values similar to mammals of the same body mass. In both camels and donkeys     increased in a nearly linear fashion over the range of exercise speeds. The minimum COT_tot of camels in the walking and pacing gaits were not significantly different ( P =0.27). Similarly, donkeys exhibited no significant difference ( P =0.09) in the minimum COT_tot while walking and trotting. In both camels and donkeys, the minimum COT_tot was significantly ( P <0.05) lower than the predicted COT_tot for mammals of the same body mass. The COT_net in both camels and donkeys was determined to be gait dependent and significantly ( P <0.05) lower than the predicted minimum COT_net values for walking and running. The low COT seen in camels and donkeys results in energy and water savings.